Tech talk: Why 2v heads need more advance than 4v heads.

[5mall5nail5]

Was talking to a buddy the other day about timing figures (he has a supercharged LS1). We were just bouncing timing values off of one another and, as can be predicted, he was saying he runs around 20 - 25 degrees of advance where we run 14 - 16 degrees of advance (considering other factors moot). We both agreed it's due to the combustion chamber efficiency mostly but I couldn't think of a good way to visualize why. I was browsing through other images I have saved and found it - thought people might find it interesting and it might give some guys a visualization of why M20/M30 maps have so much more ignition advance compared to 4 valve motors.

The goal is to time your ignition so that the flame propagates in time near the end of the compression stroke. The mixture takes some time to burn and produce the explosion, so too soon and you risk sparking the mixture while the crank is still coming up, and too late and you blow fire out of the exhaust manifolds.

So why is it that a 2v head is "less efficient" than a 4v head? This image makes it clear:

http://jonkensy.com/gallery/albums/userpics/10001/headspeed.JPG

What this image is showing is not necessarily 2v vs 4v chambers. It's showing flame propagation based on spark plug location (which is driven by valve count and placement). So, for instance, the first row is degrees in crank angle after a spark in a head with an offset spark plug. You can see that 25 degrees of rotation after the initial spark and the flame has still not fully propagated.

The second row shows more swirl in the chamber with the same offset plug position. Swirl is important on an indirect injection motor. The fuel is injected and vaporized ahead of the hot intake valve and is sucked in by the engine. Combustion chamber geometry can induce a swirling action by which the mixture is distributed more throughout the chamber. Swirling and port design can also increase the velocity by which the mixture is ingested. You can see that in the second row of images the flame has propagated more. The 3rd row induces more swirl and the flame is propagating faster yet. The first three rows represent an offset spark plug in a chamber.

The 4th row is pertinent to all with a centralized plug. Granted, some combustion chambers in a 4v central plug motor are created more efficiently than others but this is a generalized explanation. You can see that the mixture lights up really fast compared to the off-center plug chamber.

Finally, at the bottom, is a multi-plug motor. Some manufacturers choose to use a 2nd plug in a relatively "inefficient" head to maximize the ability to burn the fuel faster and complete. Porsche engines do this frequently. 2 plugs per cylinder have both advantages and disadvantages. The advantage is you can stagger plug fire with EFI solutions or vary plug fire sync throughout the powerband based on velocity through the chamber. Disadvantages are 2x the number of plugs, wires, etc. which generate more ignition noise and involve more maintenance.

So the reason why a 4v motor might only want 20 degrees where a 2v motor might want 35 degrees is because the flame moves slower through the chamber in a 2v motor and that delta of 15 degrees (hypothetical figures used). So to time it such that the flame is at its most complete state at the end of the compression stroke the initial spark needs to occur that many degrees in advance.

Just thought some one might find this visual explanation useful.

[BobRoss]

http://badassmotherfuckers.org/image.axd?picture=2011%2F3%2F1299264930661.jpg

[5mall5nail5]

This thread also kind of serves for someone who may or may not have loaded a 2v timing map into an ECU for a 4v turbo motor...

[wazzu70]

You mean i can't use a timing map from another motor? Dang :)

I have seen the flame front image before, its quite cool. I read a book long ago about some of the IC testing done at MIT. Some very cool stuff. Lots of studies on combustion chamber shape, timing advance, plug location, complete burn, flame speed, ect.

Too bad it was an older study with a 2v head.

[bawareca]

I dont know what M30 guys are running,but I rarely go over 20 degree on a full load with M20.BMW engines have been always significant for their combustion chamber shape and optimised combustion process(each of it's era).That is one of the reasons why they are so friendly to FI out of the box.
There is no doubt 4 valve engines are much more efficient but the difference is not that huge.You 2D example is interesting,but it doesnt show the complete picture.If you imagine the combustion chamber in 3D you will see that the spark plug is still close to the wall,not in the geometrical center of the chamber.Much better than the 2 valve design,but not 2 times better.
Also the head and the piston are shaped in a way to "move" the chamber close to the spark plug.The furthest end has almost no volume in it.

[bmmrr]

if we retard too much, we loose power , reduce chamber heat but get more egt.
i wonder , Will that egt is enough to burn exhaust valves or damage some parts

[e30tomo]

Not really deep in this like you, but I've heard that some VW guys with early 4 valve engines have some crazy ignition advance numbers... Was talking with some guy who drives an Opel C20LET powered car, and he was like what is that with VW's, they can use much more advance than his engine and BMW's... But C20LET and M/S 50/52 combustion chambers look very similar, and all of them, including VW are with centered spark plug, but VW's chamber is a little different...

VW

http://www.homepages.lu/marcods/Motor/KR_1.jpg


Opel

http://imgc.classistatic.com/cps/blnc/120220/651r1/4941d05_23.jpeg


And, guess which :D

http://bild4.qimage.de/zylinderkopf-bmw-e39-foto-bild-55624644.jpg


However, it can be 17 deg and 30 deg, it's good till it makes pauwa and your engine is still in one piece :)

[Captain Bondo]

\
So the reason why a 4v motor might only want 20 degrees where a 2v motor might want 35 degrees is because the flame moves slower through the chamber in a 2v motor and that delta of 15 degrees (hypothetical figures used). So to time it such that the flame is at its most complete state at the end of the compression stroke the initial spark needs to occur that many degrees in advance.

Just thought some one might find this visual explanation useful.

Great post.

Keep in mind though, it's not that the flame necessarily moves slower, it just has further to move in order for the burn to be complete and so the burn takes more time. Subtle but significant difference.

Worth noting mainly becuase flame speed itself is its own variable, based mostly on AFR.

[YellowBed]

I use 25* on an m30 (old bmw engine from a distant past) and raise it up to 27 after 6k.

What do m50s like?

[Lurker27]

I use 25* on an m30 (old bmw engine from a distant past) and raise it up to 27 after 6k.

What do m50s like?

At what MAP pressure, though?

[SiGmA]

YellowBed - Mid-teens like Jon said.

[RK-Tunes]

It depends on the set up.
here is what ive gained from my recent experiences--

17 psi at 515whp on a m52 at 9* mid range and 13 at redline I saw no knock and the car could have taken 2-3* more timing easy. This a a efficient set up.

on a less efficent set up at 20psi with a pt61 the car would have slight knock at over 9* in the midrange.

With 630whp on a 3.2 it was at 20psi it was at 8* mid range no knock.

At 14psi with 450whp 13-14 degrees in the midrange and 20 up top doesn't knock. This is with a efficient set up. With a cast manifold/ smaller intercooler expect 1-3 degrees less timing.

[BoostedE21]

I forget what I run through my powerband, but I can post my "map/tune" for my timing if you like (yes from my gameboy EFI :stickoutt)

Also, great post. Definitely good insight I never thought or knew about.

[GG///M3]

I usually go for 29 * of timing everywhere when using forged internals from unicorn pre-mix parts.

[5mall5nail5]

I dont know what M30 guys are running,but I rarely go over 20 degree on a full load with M20.BMW engines have been always significant for their combustion chamber shape and optimised combustion process(each of it's era).That is one of the reasons why they are so friendly to FI out of the box.
There is no doubt 4 valve engines are much more efficient but the difference is not that huge.You 2D example is interesting,but it doesnt show the complete picture.If you imagine the combustion chamber in 3D you will see that the spark plug is still close to the wall,not in the geometrical center of the chamber.Much better than the 2 valve design,but not 2 times better.
Also the head and the piston are shaped in a way to "move" the chamber close to the spark plug.The furthest end has almost no volume in it.

I personally disagree - the difference is huge. Having tuned my own car (when back on a holset) and a buddies M20 on a similar holset, the power bands were completely different with the M50 being much stronger. I don't follow you close to the wall statement - the spark plug on an M50 motor is equidistant to the cylinder wall from any other point on the wall. It doesn't much matter whether it has significant volume or not - we're talking about a compressed combustible mixture - it still takes time for the flame front to engulf the entire combustion chamber on the off-set 2v motors.


if we retard too much, we loose power , reduce chamber heat but get more egt.
i wonder , Will that egt is enough to burn exhaust valves or damage some parts

Yes - excessively retarded timing figures will shake and bake the out side.


Not really deep in this like you, but I've heard that some VW guys with early 4 valve engines have some crazy ignition advance numbers... Was talking with some guy who drives an Opel C20LET powered car, and he was like what is that with VW's, they can use much more advance than his engine and BMW's... But C20LET and M/S 50/52 combustion chambers look very similar, and all of them, including VW are with centered spark plug, but VW's chamber is a little different...

However, it can be 17 deg and 30 deg, it's good till it makes pauwa and your engine is still in one piece :)

Yeah I was more or less comparing the BMW engines. The older 16v heads from the VWs are a little odd because their chambers are so flat.


Great post.

Keep in mind though, it's not that the flame necessarily moves slower, it just has further to move in order for the burn to be complete and so the burn takes more time. Subtle but significant difference.

Worth noting mainly becuase flame speed itself is its own variable, based mostly on AFR.

I don't mean speed as in velocity so much as I mean how distant the initial spark must spread to engulf the entire mixture.


It depends on the set up.
here is what ive gained from my recent experiences--

17 psi at 515whp on a m52 at 9* mid range and 13 at redline I saw no knocked and the car could have taken 2-3* more timing easy. This a a efficent set up.

on a less efficent set up at 20psi with a pt61 the car would have slight knock at over 9* in the midrange.

With 630whp on a 3.2 it was at 20psi it was at 8* mid range no knock.

At 14psi with 450whp 13-14 degrees in the midrange and 20 up top doesn't knock. This is with a efficent set up. With a cast manifold/ smaller intercooler expect 1-3 degrees less timing.

You are running timing figures that I run at 30 psi on pump gas w/ methanol. Extremely soft.


I forget what I run through my powerband, but I can post my "map/tune" for my timing if you like (yes from my gameboy EFI :stickoutt)

Also, great post. Definitely good insight I never thought or knew about.

Post it up!

[good & tight]

I posted this awhile ago, this is my timing table for the M30 turbo running E85.

Keep in mind a top fuel dragster is a 2V engine and makes around 6000+hp.
Show me a 4V engine that can do that:stickoutt



http://i3.photobucket.com/albums/y83/lisaotis/dynospark-2.jpg

[5mall5nail5]

I posted this awhile ago, this is my timing table for the M30 turbo running E85.

Keep in mind a top fuel dragster is a 2V engine and makes around 6000+hp.
Show me a 4V engine that can do that:stickoutt



http://i3.photobucket.com/albums/y83/lisaotis/dynospark-2.jpg

Otis - you're confusing this topic. It's not about what can make more power. It's about timing and why a 2v requires more than 4v.

At 300 kpa M50s like 12 advance... roughly half of what you're running.

[bawareca]

Otis - you're confusing this topic. It's not about what can make more power. It's about timing and why a 2v requires more than 4v.

At 300 kpa M50s like 12 advance... roughly half of what you're running.

How do you determine what it "needs"?Do you say that if you go 15 degrees it will go down on the power?
I dont have much experience with 24 v motors and I am curious.Best bet will be to see some factory maps deciphered.

[5mall5nail5]

How do you determine what it "needs"?Do you say that if you go 15 degrees it will go down on the power?
I dont have much experience with 24 v motors and I am curious.Best bet will be to see some factory maps deciphered.

If I run an M30 and M50 at the same press and RPM the M30 might require as much as 2x the amount of timing advance (ignoring a lot of minute details, so work with me).

[good & tight]

Otis - you're confusing this topic. It's not about what can make more power. It's about timing and why a 2v requires more than 4v.

At 300 kpa M50s like 12 advance... roughly half of what you're running.
Not confused, just sayin. :)

The limit I found on 93 octane was 19* at 230kpa, after that I switched to E85.

[5mall5nail5]

Not confused, just sayin. :)

The limit I found on 93 octane was 19* at 230kpa, after that I switched to E85.

I assume that was without water/meth? My M50 was well within limits on 93 octane + 50:50 water meth at 9 degrees at 299 KPA. I went to 11 degrees only to slip the clutch worse.

[bawareca]

Your comparison with M30 may be correct,but i can assure you that M20 and M30 are different beasts.
And you didnt enlighten us how did you get to the magical number 12.

[5mall5nail5]

Your comparison with M30 may be correct,but i can assure you that M20 and M30 are different beasts.
And you didnt enlighten us how did you get to the magical number 12.

An M20 is not a different beast. Look at a timing map for each.

How I got to the magical number 12? It's called tuning my friend.

[good & tight]

I assume that was without water/meth? My M50 was well within limits on 93 octane + 50:50 water meth at 9 degrees at 299 KPA. I went to 11 degrees only to slip the clutch worse.
Correct no water/meth. 19* was it's max limit (showing light signs of det), I bumped it 2* more and lifted the head.

[5mall5nail5]

Correct no water/meth. 19* was it's max limit (showing light signs of det), I bumped it 2* more and lifted the head.

Heh - ouch.

[GG///M3]

Rape * timing is best

[bawareca]

........... It's called tuning my friend.
I have heard that word once,I have to google it.
My question was,is it detonation limited at 12,or it is where it makes most power?

[good & tight]

Heh - ouch.
Not to mention a few 24psi spikes trying to figure out the boost controller.:lol
But yea 19psi is the limit.

[5mall5nail5]

I have heard that word once,I have to google it.
My question was,is it detonation limited at 12,or it is where it makes most power?

My personal car was not detonating, but my clutch couldn't cope. Based on lower pressure figures 12 seems about where I'd want to be.


Not to mention a few 24psi spikes trying to figure out the boost controller.:lol
But yea 19psi is the limit.

Yah - gotta tweak that overboost setting ;)

[Lurker27]

My question is this: We know that 2v heads present much more restriction, which, in comparing megasquirt tables (you're the one to talk to about this, I think) shows up as higher VE. It's not just swirl/tumble that the 24v heads have an advantage in (though I think you're right that the combustion dynamics are what is, partially, what is demanding more timing. If the cylinder pressure is less due to lower VE, then you'll need more timing anyway, right?

So if we normalize to VE*Manifold pressure...how does the comparison look then? And more importantly, does this limit power in practice? I'm assuming that a less even flame front propagating more slowly in the chamber somewhat increases the tendency to detonate at a given cylinder pressure, but does this effect the tq capability of the engines in question?

[Robstah]

M20s are in-efficient. Period. Boost fixes a lot of those issues.

I can has 32v LSX?

http://www.araoengineering.com/lsx.htm

They claim 100hp right off the bat.

My dream engine is a 32v flat plane crank LSX that revs to 9000RPM. I could care less about the power it makes.

[bawareca]

M20s are in-efficient. Period. Boost fixes a lot of those issues.

.........

Compared to what?To be fair,you can compare it to something of it's era,i.e. late 70s:alright


...............
I can has 32v LSX?

http://www.araoengineering.com/lsx.htm

They claim 100hp right off the bat.

My dream engine is a 32v flat plane crank LSX that revs to 9000RPM. I could care less about the power it makes.
I was left with the impression that is a BMW forum;)

[RK-Tunes]

You are running timing figures that I run at 30 psi on pump gas w/ methanol. Extremely soft.

Pump gas and Meth is different from just pump gas.

Also I have done lots of testing and i have first hand seen the differences between mbt and what my datalogger is reading from the knock sensors. A fee extra degrees making 10-15whp more is not worth putting a motor that close to knocking.

I am extreamly happy with the horsepower and torque numbers I end at.. I look to make the maximum safe power.

[Bwaterman]

Very interesting graphics Jon, I hadn't considered how significant swirl in the combustion chamber was to burn rate. Until now I had mostly considered CC shape (ie pent roof, hemi etc) for flame propagation.

For those who have not read it, this article about knock and pre-ignition is related and talks about burn rates affecting octane requirement and CR. http://www.contactmagazine.com/Issue54/EngineBasics.html

[RK-Tunes]

Also. Very nice information in this thread jon.

[BobRoss]

Does compression ratio not come into play here?
not many boosted 2v motors around here running more than 8.8:1 that i know of?

[bawareca]

http://www.e30tech.com/forum/showthread.php?t=33028

That is very informative thread with many M20 timing maps posted.Most guys(including me) run ~20 degree @200 kpa and ~ 14 @ 250 kpa with pump gas.if i make the approximation it should be 8-11 degree @300 kpa.I dont see how one can run half of that timing and make reasonable power.
I wanted to find 24v map for comparison,but looks like they are very secret :gasthrowe

[Bwaterman]

Does compression ratio not come into play here?
not many boosted 2v motors around here running more than 8.8:1 that i know of?

It does come into play but this thread is focused mainly on CC swirl and spark plug location.

High CR will increase flame speed but in a 2V hemi head the flame has to travel a long way around and over the dome of the piston which means a longer burn. Having a longer burn will increase heat buildup and increase the potential for detonation. That is why a pent roof chamber can safely run a higher CR than a domed head and it will require less timing to achieve peak cyl pressure at 14-15deg ATDC

[bawareca]

Does compression ratio not come into play here?
not many boosted 2v motors around here running more than 8.8:1 that i know of?

i run 9.5:1 currently,but didnt go the dyno yet.I will have the results in a month.

[VwAlex]

Jon = hpf fanboi his opinion = no value

[gstuning]

It´s got more to do with the overall turbulence rather then swirl.

I.e the tiny TINY eddy currents created as the piston is pushing up on the mixture.

Two things create turbulence, air density and engine speed.

Air density then breaks down into : A combination of air volume and compression ratio.

Engine speed creates turbulence thanks to faster moving piston.

Those two also dictate why ignition advance must change with fixed VE over a range of engine speed.

The flame propogation speed is the results of turbulence. As you start burning a little eddy current it rotates and ignites the adjacent ones, the faster they spin the faster they come in literal contact with other eddy currents to ignite them.

I think the easiest way to visually this is the mythbusters episode when they where burning gas to blow out pot hole covers, when they stuck a whole bunch of springs and stuff into the pipes that created turbulence as the gas infront of the burn was getting pushed by the rise in pressure behind it, when it moved past the springs little eddy currents where made, when the flame finally cought up with the now turbulent air the flame propogation accelerated faster and faster. Squish area also helps with this in the final push of the piston to the top.


If we imagine a fixed engine with nothing changing but engine speed you will need higher and higher ignition advance to account for the ignition delay which is a fixed time so that peak pressure can occur at the right moment.

In the real world two things happen, VE drops after peak torque which causes a need for more advance, however with more engine speed you also get more natural turbulence which requires less advance to be put in. The results are that sometimes after peak torque that ignition advance doesn´t need to be raised as much or at all.

The less the ignition advance for MBT the higher is the turbulence design of the cylinder, and with that higher efficiency for the given airflow amount as you are creating less work against the engine while it´s on the compression stroke, giving you more final output.

Given a M20 and M50 engine with the same amount of air density, compression ratio and engine speed the M50 will be more efficient due to plug placement. The M20 is designed with swirl inducing pistons and chamber which helps its efficiency but the M50 has tumble (pent roof) designed which starts turbulence sooner in the piston stroke which ultimately helps with flame propogation.

[bmmrr]

Pump gas and Meth is different from just pump gas.

Also I have done lots of testing and i have first hand seen the differences between mbt and what my datalogger is reading from the knock sensors. A fee extra degrees making 10-15whp more is not worth putting a motor that close to knocking.

I am extreamly happy with the horsepower and torque numbers I end at.. I look to make the maximum safe power.

Are these knock sensors oem sensors and oem ecu?

I would like to know , if oem sensors can detect knock when you convert n/a car to turbo car? I mean, I heard that knock frequency changes when the car is boosted. Or can the oem sensors think, the car is knocking but while it is in boost and not knocking.

[Robstah]

Compared to what?To be fair,you can compare it to something of it's era,i.e. late 70s:alright


I was left with the impression that is a BMW forum;)

We are talking about 2 valve heads vs. 4 valve heads. Someone has already posted pictures of other make 4 valve heads. :shifty

My point with the M20 and all 2 valve motors is that boost tends to help with the inefficiencies. NA applications will see the biggest benefit between 2 valve and 4 valve heads.

[BadBoostedBmwM3]

So the reason why a 4v motor might only want 20 degrees where a 2v motor might want 35 degrees is because the flame moves slower through the chamber in a 2v motor and that delta of 15 degrees (hypothetical figures used). So to time it such that the flame is at its most complete state at the end of the compression stroke the initial spark needs to occur that many degrees in advance.

Just thought some one might find this visual explanation useful.

The meat and potatoes as some would say.

It depends on the set up.
here is what ive gained from my recent experiences--

17 psi at 515whp on a m52 at 9* mid range and 13 at redline I saw no knock and the car could have taken 2-3* more timing easy. This a a efficient set up.

on a less efficent set up at 20psi with a pt61 the car would have slight knock at over 9* in the midrange.

With 630whp on a 3.2 it was at 20psi it was at 8* mid range no knock.

At 14psi with 450whp 13-14 degrees in the midrange and 20 up top doesn't knock. This is with a efficient set up. With a cast manifold/ smaller intercooler expect 1-3 degrees less timing.

Jordan, I'm not questioning your tuning abilities (obviously you've done well thus far), but isn't that very soft even for pump gas? Most people post around ~13*.
Btw, I'm not a tuner, but in the cases I've seen with soft timing, the EGTs were on the high side. How were yours?
Also, are you calling "midrange" where torque crosses over the power line?


M20s are in-efficient. Period. Boost fixes a lot of those issues.

I can has 32v LSX?

http://www.araoengineering.com/lsx.htm

They claim 100hp right off the bat.

My dream engine is a 32v flat plane crank LSX that revs to 9000RPM. I could care less about the power it makes.

Off topic but I bet that would sound awesome!
I'm not too familiar with flat plane cranks but what are their power making abilities like?

[5mall5nail5]

Jon = hpf fanboi his opinion = no value

LOL you can't be serious!


Last time I checked top fuel and funny car were 2 valve motors they are in the 8-10k HP range...

Additionally with nitro meth being the fuel they run they are required to start their ignition insanely early something like 30 degrees at idle. Can it be called inefficient to burn that early sure but last time I checked the folks concerned with mpg are rarely concerned with power

I’m in no way advocating that 2 valves are inherently better than 4 valves - I’m just playing devil’s advocate.

I do believe that there are massive benefits to be had from 4v or even 5v heads but I certainly don't believe that there is inherently anything wrong with the m20/m30/top fuel BBM (big block mopar), because as we all know forced induction has long since been an equalizer of poor intake/head design

Lastly and certainly not least, since there seems to be so much bashing of the old and so little appreciation of the old(er) engines just remember Offenhauser turbocharged a 4 cylinder 4 valve head back in the 19-teens and made over 1000 HP it evolved into the Indy race engines of the 1980's. Had safety been on par we probably would still be running those engines in one variant or another.

Again... some people need to read the title. It's not about "how many valves are in engines making the most power". Turbo fan engines make way more power than a top fuel motor. That's not what we're talking about. We're talking about why 2v heads require more timing to make the same effect as a 4v head.... on our BMWs since we're on a BMW forum (though it loosely applies to all combustion chambers). We're not talking about more or less power. We're talking about ignition timing tendencies.



Given a M20 and M50 engine with the same amount of air density, compression ratio and engine speed the M50 will be more efficient due to plug placement. The M20 is designed with swirl inducing pistons and chamber which helps its efficiency but the M50 has tumble (pent roof) designed which starts turbulence sooner in the piston stroke which ultimately helps with flame propogation.

Thanks for your input Gunni. Always appreciated.

[bawareca]

Given a M20 and M50 engine with the same amount of air density, compression ratio and engine speed the M50 will be more efficient due to plug placement. The M20 is designed with swirl inducing pistons and chamber which helps its efficiency but the M50 has tumble (pent roof) designed which starts turbulence sooner in the piston stroke which ultimately helps with flame propogation.


Thanks for your input Gunni. Always appreciated.
No one is arguing that M50 is more efficient than M20 and M30.Even if I never saw any of those i will tell that the newer generation [BMW] engine is more efficient than the old one.With other manufacturers 4 V design may be superior in light years than the 2V, but that is not the case with BMW.As one can see from the link with the M20 ignition tables the numbers are pretty close,so are the power levels.

[NOTORIOUS VR]

No one is arguing that M50 is more efficient than M20 and M30.Even if I never saw any of those i will tell that the newer generation [BMW] engine is more efficient than the old one.With other manufacturers 4 V design may be superior in light years than the 2V, but that is not the case with BMW.As one can see from the link with the M20 ignition tables the numbers are pretty close,so are the power levels.

Your problem (along with many others here) is this...

You're not seeing why most 2V engine designs require more advance then a 4V engine design.

Stop comparing the timing tables you see on E30tech to others.... the ones you see for "running" setups will be influenced by other factors.

5mall5nail5 and Gunni are completely correct here.

[bawareca]

Your problem (along with many others here) is this...

You're not seeing why most 2V engine designs require more advance then a 4V engine design.

Stop comparing the timing tables you see on E30tech to others.... the ones you see for "running" setups will be influenced by other factors.

5mall5nail5 and Gunni are completely correct here.

But your post is just some words put in one sentence,and the title of that thread is TECH TALK.I can say that you have never saw a piston in your life,but that has nothing to do with that thread.What I "see on E30tech" is what I see on my map,and is a good refference point.At least it is more than just say someone "You dont know,you dont see....."
What John said is that M20 needs 2 times more timing than M50,which i dont agree.Plus he never explored the limit,where the power will start going down because he is "clutch limited",according to his post.

[5mall5nail5]

But your post is just some words put in one sentence,and the title of that thread is TECH TALK.I can say that you have never saw a piston in your life,but that has nothing to do with that thread.What I "see on E30tech" is what I see on my map,and is a good refference point.At least it is more than just say someone "You dont know,you dont see....."
What John said is that M20 needs 2 times more timing than M50,which i dont agree.Plus he never explored the limit,where the power will start going down because he is "clutch limited",according to his post.

I've tuned and helped tune about a dozen or more M50-based motors on standalones. I am not going by just my own engine here. An M20 requires more timing than M50 to do the same work. Fact.

[BoostedE21]

Post it up!

I think this is still my tune (car is in the shop still getting the new motor)
My E21 tune (https://spreadsheets.google.com/spreadsheet/lv?key=0AsC5708CaXzYdDdYZTB2VUpucnl3aUU0MEQzc29WV2 c&hl=en).

This is based on feel and sound, no dyno tune. Feedback always welcome.

[bawareca]

I've tuned and helped tune about a dozen or more M50-based motors on standalones. I am not going by just my own engine here. An M20 requires more timing than M50 to do the same work. Fact.

Agreed 100%,no argue here.Also agree that M30 may require close to double the timing of the M50 at times(of course those are all approximations).M20 is a different beast and not that far behind M50.


.........
Also the head and the piston are shaped in a way to "move" the chamber close to the spark plug.The furthest end has almost no volume in it.


. ..........It doesn't much matter whether it has significant volume or not - we're talking about a compressed combustible mixture - it still takes time for the flame front to engulf the entire combustion chamber on the off-set 2v motors...........
!

However the milestone of the small- six engines was yet to come: the 325i unit (325is in the states). This head (casting number 1705885) has large U-shaped ports (about 37mm by 37mm) and a slightly larger combustion chamber volume of 40cc but follows a new combustion chamber philosophy. Several studies have shown that an open chamber design (basically spherical in shape) has a faster burn rate (desirable in terms of avoiding detonation and good for efficiency) than either a classical hemi chamber (such as that used on tha Alfa V-6) or a Heron chamber(bowl in piston such as that used in VW Golfs/Rabbits). On the 1705885 head there is a dish in the piston within a dome! This is hard to explain unless it has been seen. Basically BMW engineers probably reasoned out that it would not be possible to move the spark plugs to a more central position (desirable in terms on thermodynamic efficiency) and keep the cylinder configuration the same so they moved the bulk of the chamber volume around the spark plug (which consisted of the offset dish in the piston and the hemi in the head) all the rest became squish zones. This is an outstandingly efficient package. The stroke was made shorter than the old 323i while the con rods were lengthened to increase rod to stroke ratio to reduce friction/increase top end poke. The compression ratio was 9.7:1 and 8.8:1 for the US market/later European spec. The lobe centerline angle of the camshaft was reduced again to 108 degrees but so was the duration. The late Eta used the large port "885 head (often called the 'supereta'). I have no knowledge on what kind of piston or cam timing that has been used.

(copied from that site- http://e21.tricord.be/e21/about/m20/cylinder-heads.php )

[gstuning]

bore diamater = more advance required.

the M30 advance numbers are in no way comparable to M50´s and M20´s.

[DarkSideofWill]

Was talking to a buddy the other day about timing figures (he has a supercharged LS1). We were just bouncing timing values off of one another and, as can be predicted, he was saying he runs around 20 - 25 degrees of advance where we run 14 - 16 degrees of advance (considering other factors moot). We both agreed it's due to the combustion chamber efficiency mostly but I couldn't think of a good way to visualize why. I was browsing through other images I have saved and found it - thought people might find it interesting and it might give some guys a visualization of why M20/M30 maps have so much more ignition advance compared to 4 valve motors.

The goal is to time your ignition so that the flame propagates in time near the end of the compression stroke. The mixture takes some time to burn and produce the explosion, so too soon and you risk sparking the mixture while the crank is still coming up, and too late and you blow fire out of the exhaust manifolds.

So why is it that a 2v head is "less efficient" than a 4v head? This image makes it clear:

http://jonkensy.com/gallery/albums/userpics/10001/headspeed.JPG

What this image is showing is not necessarily 2v vs 4v chambers. It's showing flame propagation based on spark plug location (which is driven by valve count and placement). So, for instance, the first row is degrees in crank angle after a spark in a head with an offset spark plug. You can see that 25 degrees of rotation after the initial spark and the flame has still not fully propagated.

The second row shows more swirl in the chamber with the same offset plug position. Swirl is important on an indirect injection motor. The fuel is injected and vaporized ahead of the hot intake valve and is sucked in by the engine. Combustion chamber geometry can induce a swirling action by which the mixture is distributed more throughout the chamber. Swirling and port design can also increase the velocity by which the mixture is ingested. You can see that in the second row of images the flame has propagated more. The 3rd row induces more swirl and the flame is propagating faster yet. The first three rows represent an offset spark plug in a chamber.

The 4th row is pertinent to all with a centralized plug. Granted, some combustion chambers in a 4v central plug motor are created more efficiently than others but this is a generalized explanation. You can see that the mixture lights up really fast compared to the off-center plug chamber.

Finally, at the bottom, is a multi-plug motor. Some manufacturers choose to use a 2nd plug in a relatively "inefficient" head to maximize the ability to burn the fuel faster and complete. Porsche engines do this frequently. 2 plugs per cylinder have both advantages and disadvantages. The advantage is you can stagger plug fire with EFI solutions or vary plug fire sync throughout the powerband based on velocity through the chamber. Disadvantages are 2x the number of plugs, wires, etc. which generate more ignition noise and involve more maintenance.

So the reason why a 4v motor might only want 20 degrees where a 2v motor might want 35 degrees is because the flame moves slower through the chamber in a 2v motor and that delta of 15 degrees (hypothetical figures used). So to time it such that the flame is at its most complete state at the end of the compression stroke the initial spark needs to occur that many degrees in advance.

Just thought some one might find this visual explanation useful.

A few things to keep in mind:

-An engine is a system, and system level performance characteristics very seldom trace down to one variable

-The M20/M50 is the only apples/apples comparison mentioned so far. Most M30's have a significantly larger bore (92mm) than the M50 (84-86.5) and the LS1's bore is the grand canyon by comparison (99mm to 101.6+). Also, only similar boost and fuel can get to the comparison you're trying to get to.

-The LS1 chamber is extremely efficient. GM and BMW have pretty much the same design muscle in terms of CFD. The 2V *inline* valve chamber allows a very large fraction of the bore to be quench/squish, which increases mixture motion significantly. The offset intake valve also promotes good swirl.

-BMW's offset canted valve 2V chamber is a mess compared to the LSx chambers. The high valve angles make the chamber deep and the cant makes it large so that it can't have good quench/squish. The minimal valve offset means it can't have good swirl either. These chambers need domed pistons to achieve high compression ratios, resulting in poor surface area to volume ratios.

-The M50 chamber has a shallow valve angle and pent roof plug. The pent roof directs mixture toward the plug similar to quench/squish but with lower velocity. The entire perimeter of the bore is quench pad. The chamber isn't too deep and isn't too shallow. When viewed from the side, the plug is at the upper edge of the chamber, but the chamber's vertical dimension is reasonable.

-The VW chambers mentioned above probably have poor surface area to volume ratio because they're flat. In the pics, they also appear not to have quench/squish pads on the intake side.

-While there is a "sweet spot" for the fraction of the fuel that is vaporized in the port, it is possible vaporize too much and displace intake air. Every engine likes something a little different, but there are several variables in mixture quality: vapor fraction, droplet size, homogeneity, temperature, density, etc. It's very difficult to manipulate these variables when using port fuel injection without moving the injector from the stock location. It's surprisingly easy to manipulate mixture quality with carb mods, but the carb doesn't meter the fuel as precisely as EFI, either.

[bawareca]

^^^^ Now that is a tech talk :thumbup:

[5mall5nail5]

^^^^ Now that is a tech talk :thumbup:

Why? because I didn't say it? He reiterated most of what I said.

Sounds like you only have an issue when I say things. An M20 takes more advance than an M50. An M10 takes more advance than an M50. And M30 takes more advance than an M50. 2v heads take more advance than 4v heads - it's a fact and the first post outlines why.

[bawareca]

^^^But that is pointless,a fact that no one argue with.
And you are claiming in your first posts that M20 and M30 are the same piece of $$h.t and need twice the timing M50 needs.
Also when i wrote in my post that the spark plug is actually close to the top of the CC than in the middle you answered that there is no such thing.

[5mall5nail5]

^^^But that is pointless,a fact that no one argue with.
And you are claiming in your first posts that M20 and M30 are the same piece of $$h.t and need twice the timing M50 needs.
Also when i wrote in my post that the spark plug is actually close to the top of the CC than in the middle you answered that there is no such thing.

:confused

I didn't call anything a POS.

I think you need to focus more on what I said and less on what you think I said.

[YellowBed]

but but but but..... :embarrasm

[bawareca]

:confused

I didn't call anything a POS.

I think you need to focus more on what I said and less on what you think I said.

Thank you for pointing out that english is not my native language.I did take my time to learn it fluently,and as I may have some 'glitches' here and there that is not the problem here.If you go back and reread the thread you will find that there is a big change in your claims from page 1 to page 3.
As in the HPF threads you only comment on what helps your arguments,and just leave the 'uncomfortable' comments in the dust.
As I wrote before I have respect for your knowledge and experience,but I dont like discussions where the main argument is "It is so because I said so...",so obviously I wont be participating such a debates anymore.
Oh,my project is M20 because I like it,not because I cant afford M5X,M6X or S whatever.I can imagine someone having M50,but drooling over Supras,as an example, could be pretty stressed.

[5mall5nail5]

Thank you for pointing out that english is not my native language.I did take my time to learn it fluently,and as I may have some 'glitches' here and there that is not the problem here.If you go back and reread the thread you will find that there is a big change in your claims from page 1 to page 3.
As in the HPF threads you only comment on what helps your arguments,and just leave the 'uncomfortable' comments in the dust.
As I wrote before I have respect for your knowledge and experience,but I dont like discussions where the main argument is "It is so because I said so...",so obviously I wont be participating such a debates anymore.
Oh,my project is M20 because I like it,not because I cant afford M5X,M6X or S whatever.I can imagine someone having M50,but drooling over Supras,as an example, could be pretty stressed.

LOL ok bud. Whatever you say. You're right. M20s... and M30s.... M50s... they're all the same.

It isn't because I say so. It's because physics never sleeps. I don't know what else to tell you. If you don't want to believe it, then go run an M50 at 20 psi at 25 degrees. I don't care.

[YellowBed]

keep shut a set of intake/exhaust valves on the m50 and see if it likes
the same timing as an m20. :eek:

[dohcdoh]

Top fuel will never switch to turbos. google is your friend :)
" NHRA rule book says that for Top Fuel dragsters, the forced induction engine is restricted to Roots-type supercharger, rotor helix angle not to exceed that of standard 71-series GM-type rotor. Turbocharger and/or centrifugal supercharger are prohibited. "

[5mall5nail5]

I don't believe he's advocating that they are all the same, I believe he's advocating that because you've never pushed an m20 to its limits that you don't necessarily have the right to say unilaterally that the m20/m30/m10 ALWAYS require twice the timing of the m50.

That said you do have experience with the m50 and in YOUR m50 vs. your buddies m20 (we've all got a buddy who's got something) that had similar - albeit not identical setups, and it made power differently. That’s all fine and dandy but again I think you're missing the point that all engines make power.


Additionally top fuel engines produce 1000+ HP per cylinder, or said another way 1000+HP per every 62.5 cubic inches, or 1000+hp per liter what other engine (using pistons and only 500 cubic inches) is in that league?


I am in no way advocating that superchargers are more efficient or that turbo has less potential - I give it 5 years before top fuel makes the switch to turbo or turbo/supercharger hybrid engines.


Bud. It's documented. I've built over 30 ECUs. It takes roughly 2x the timing in an M20 and M30 to do the same power figures, NA, than an M50. Its a fact. There's no arguing it. Go look at published ignition maps on E30tech or R3v. I've got experience tuning a dozen M50 based motors - maybe more. M30s. M20s. S38s. M60s. There's a CONSTANT trend. That's why it's physics. It's repeatable.

Again what on gods green earth does a top fuel motor have to do with a 2 or 4v bmw motor discussion?

Seriously sometimes I feel like people don't read, and just argue.

[bawareca]

LOL ok bud. Whatever you say. You're right. M20s... and M30s.... M50s... they're all the same.

It isn't because I say so. It's because physics never sleeps. I don't know what else to tell you. If you don't want to believe it, then go run an M50 at 20 psi at 25 degrees. I don't care.

I dont think you can make that timing even on M20,but it may be up for some great numbers,briefly ;) I am not really interested in m50 as it is too heavy for the purpose I need it,but Iwas considering spending a small fortune to build M54,but extensive research shows that almost none of the original parts can be used for performance.
I really like the 'evolution' in your opinions for just 3 pages,you sir rock :buttrock

[5mall5nail5]

i respectfully disagree, the topic was 2v vs 4 valve not 2v bmw vs 4v bmw

:rolleyes

http://jonkensy.com/gallery/albums/userpics/10001/Capture.JPG


Oh yeah I can see how a top fuel motor can easily be confused on Bimmerforums ... being that we run nitromethane and 2v V8's and all... yeah totally I can see why you're confused...


:rolleyes


I dont think you can make that timing even on M20,but it may be up for some great numbers,briefly ;) I am not really interested in m50 as it is too heavy for the purpose I need it,but Iwas considering spending a small fortune to build M54,but extensive research shows that almost none of the original parts can be used for performance.
I really like the 'evolution' in your opinions for just 3 pages,you sir rock :buttrock

You obviously have trouble reading if you think my opinion has evolved. I cannot help you think. I have no idea what you're reading to have come to that conclusion. There should be a comprehension test followed by a significant fee for using the internet.


why would you bother to argue NA engines in a forced induction thread.

Troll.

[5mall5nail5]

your arguement for the m60 seems like an excercise in futility i cannot think of a single (current) bmw v8 that only had 2 valves per cylinder. and by that measure you could compare it to a 2 v sbc/sbf/sbm and you would find yourself up a creek without a paddle because the american made engine make WAY more power with their 2v engines than even the s62 and even the new gen bmw twin turbo v8's (though that may not be the case for long)

I am sorry, where did I state that an m60 had 2v? Where did I say there was a 2v equivalent. Why are you arguing lol? Timing maps confirm physics. It's funny - they work hand in hand. What are you even arguing any longer?

Really? A 5.7 - 7.3L engine makes more power than a 4.9L. That's amazing - good find. The domestic two valves require more ignition advance :rofl, so that brings us back to the basis of the thread.

Isn't there like an AOL chatroom you can go argue in?

Oh I get it - livinginexile... joined march 2012... 13 posts... trolls in my build thread. trolls in my valve tech thread... ah you must be a troll.

[bawareca]

:

You obviously have trouble reading if you think my opinion has evolved. I cannot help you think. I have no idea what you're reading to have come to that conclusion. There should be a comprehension test followed by a significant fee for using the internet.


Now you can answer yourself why the other guy's post is a tech talk and most of yours isnt.
"That is well documented" equals "It is so because I said so" argument.
I am probably the next troll,because I dont agree with you.
And your opinion didnt 'evolve' ,it is just slippery.I dont know who the f**k cares about NA engine in that thread,but if you want to prove you're right you are free to post some factory maps for the spoken engines.

[5mall5nail5]

Now you can answer yourself why the other guy's post is a tech talk and most of yours isnt.
"That is well documented" equals "It is so because I said so" argument.
I am probably the next troll,because I dont agree with you.
And your opinion didnt 'evolve' ,it is just slippery.I dont know who the f**k cares about NA engine in that thread,but if you want to prove you're right you are free to post some factory maps for the spoken engines.

I think I've posted this before in another thread, but I will post it again once more:

I will not retype things over and over for you. Read my posts - then, develop a thought. I have not changed my "opinion". You can strobe a factory M20 at idle and a factory M50 at idle and see their IDLE timing is nearly double. Do it for yourself if you do not believe me. At the end of the day, everyone else here has confirmed. I don't know why you're arguing. It's not a fact because I said so, it's a fact because every single timing map in an M20 motor is running with significantly more timing advance than an M50 doing the same work.

What is there to doubt?

[DarkSideofWill]

every single timing map in an M20 motor is running with significantly more timing advance than an M50 doing the same work.


Define "the same work".

[SiGmA]

Now you can answer yourself why the other guy's post is a tech talk and most of yours isnt.
"That is well documented" equals "It is so because I said so" argument.
I am probably the next troll,because I dont agree with you.
And your opinion didnt 'evolve' ,it is just slippery.I dont know who the f**k cares about NA engine in that thread,but if you want to prove you're right you are free to post some factory maps for the spoken engines.I'm sorry man, what? This isn't because Jon said so, between an M20 and an M50, there is a factor of roughly two on the timing maps. This is in large part due to the valves, as well as other engine construction things. Its not like this is any sort of new info, Jon just posted it up with some pictures to show different flame fronts.

I really wish I had a better timing map from my car, but I don't have the ViPEC software installed anymore and don't want to deal with that tonight to get you a graph. I do have a DME timing map (WOT) overlaid on a pull, as well as Otis posted up his M30's map. Check it out.

M30
http://i3.photobucket.com/albums/y83/lisaotis/dynospark-2.jpg

M50
https://lh5.googleusercontent.com/-HQ3nQaGazNQ/StKyqCTa0jI/AAAAAAAAFWo/ZVStLx71p0o/s912/10-10-2009-4th-15deg-13psi.jpgTake a peek at Otis' idle area. About 20* on his motor. My M50 took about 9*. Very very normal for an M50.
saw this and thought i'd repost it here



sorry kevlar for copy and pasting your likeness


http://forums.bimmerforums.com/forum/vb3avatar/avatar12_11.gif (http://forums.bimmerforums.com/forum/member.php?u=12)Kevlar (http://forums.bimmerforums.com/forum/member.php?u=12) http://images.bimmerforums.com/vb3images/statusicon/user_offline.gif
Judge, Jury & Bulldozer
Administrator
Join Date: Feb 2001
Location: Fort Lauderdale, FL.
Cars: 2011 M3 Sedan
Posts: 70,349
http://images.bimmerforums.com/vb3images/misc/im_icq.gif (http://forums.bimmerforums.com/forum/showthread.php?t=1258495#) http://images.bimmerforums.com/vb3images/misc/im_aim.gif (http://forums.bimmerforums.com/forum/showthread.php?t=1258495#)

Agree to disagree ... respectfully!
It's a shame I really have to post an announcement of this nature. I would like to think that adults would be able to get along with one another and voice (http://forums.bimmerforums.com/forum/showthread.php?t=1258495#) their opinions without constantly pickign fights with one another over what they think is best.

Listen folks... everyone is entitled to their opinion. That's fine. However, please do not try to force your opinion on others. If you disagree with something they say/do, you can speak your mind, but don't follow them around the forum trying to beat sense into them because you feel that your opinion is right. If you documents to back up your opinion, great... but in the end ... people are going to do what they want to do and you can't do anything about it.

So... learn to get along or at least learn to take your drama (http://forums.bimmerforums.com/forum/showthread.php?t=1258495#) elsewhere. When I have to start kicking people out of the sandbox because they can't play nicely together, it really takes some of the fun out of all of us enthusiasts being able to discuss things together ... respectfully.

__________________Dude, what? GTFO troll.


Define "the same work".Power output.

[bawareca]

I think I've posted this before in another thread, but I will post it again once more:

I will not retype things over and over for you. Read my posts - then, develop a thought. I have not changed my "opinion". You can strobe a factory M20 at idle and a factory M50 at idle and see their IDLE timing is nearly double. .................

So that is all you got? From a thread called TECH TALK and after all that discussion you are talking about idle?Really?In that subforum?The great tuner opened a complete thread to discuss the idle timing?Now that is pathetic.That is what I call slippery.

[5mall5nail5]

So that is all you got? From a thread called TECH TALK and after all that discussion you are talking about idle?Really?In that subforum?The great tuner opened a complete thread to discuss the idle timing?Now that is pathetic.That is what I call slippery.

I am not surprised that's all you've got out of the thread. You don't seem to pay much attention.

An M20 runs 16 at idle.

An M50 runs about 9.

That's nearly 1/2 the amount of timing.

My point stands.

How about this - since you don't believe there is any difference in timing advance required (even though Gunni, an engine design engineer confirmed, but hey...) why not run an M50 map in your M20? Should make the same power right?

[SiGmA]

diyautotune's basemap for the m20 is 16 degrees at idle:redspot

if it's running 25 degrees more timing than the m50 then you must be something like -4 to -9 degrees of timing... yes jon your story is changing...My brain hurts a little more every time I read your posts.

If Jon said approx double, and DIYAutoTune suggests 16* at idle, and an M50 takes 9* or so... A factor of 0.5625 which is damn close to half, or double going the other way. But somehow you think half of 16 is -4 to -9? WTF?

[bawareca]

I am not surprised that's all you've got out of the thread. You don't seem to pay much attention.

An M20 runs 16 at idle.

An M50 runs about 9.

That's nearly 1/2 the amount of timing.

My point stands.

How about this - since you don't believe there is any difference in timing advance required (even though Gunni, an engine design engineer confirmed, but hey...) why not run an M50 map in your M20? Should make the same power right?
And you are absolutely sure about that,you can almost swear in the bible?

[5mall5nail5]

And you are absolutely sure about that,you can almost swear in the bible?

No, I am lying about M50 idle figures. :rolleyes

[bawareca]

No, I am lying about M50 idle figures. :rolleyes

You tell me.In that thread there are many M50 maps published:
http://forums.bimmerforums.com/forum/showthread.php?t=1655079
For the lazy guys I will take the freedom to quote Gunny:

As discussed in another thread there seems to be some lacking information regarding the values related to M50 based engines.


Please post your ignition table and the relevant information related to it.

Engine : M50 Non vanos, ARP and MLS
Turbo : Borg Warner S257 (57mm compressor, 63mm turbine)
Exhaust : "3
Load strategy : Speed density
Fuel : 98ron / 91mon

This table was thrown together being considered safe. It worked a treat was run to 1bar boost.

http://myndasafn.bmwkraftur.is/d/93239-1/m50ign.jpg

just for kicks here is the cars VE table.

http://myndasafn.bmwkraftur.is/d/93242-1/m50ve.jpg

And after that it ,of course,your table:

I know :)

I'd have to pull the latest map in the car but its not running much more timing. I literally took my conservative street tune to the dyno and did pulls. I think I added .5 degrees up top and the clutch let go. I was running around 300 kPA for 685 rwhp with a timing map not to dissimilar from the above.

Edit: Actually, I pulled my timing map from before the dyno (like 2 weeks before I think) and ... its even more conservative lol:

http://jonkensy.com/gallery/albums/userpics/10001/timing_pulled.JPG

I think I had it up to about 10 advance under the 315 kPA column when the clutch let go.

Imagine how much power is left on the table. I run about 22 psi on the street. The truth is its fast as is so I have a hard time tuning timing on the street. Make some edits if you want!
I still dont see 9 degree at idle,but that is probably because I cant read maps.FYI my M20 runs best at 13 degree for what it is worth.

[5mall5nail5]

You tell me.In that thread there are many M50 maps published:
http://forums.bimmerforums.com/forum/showthread.php?t=1655079
For the lazy guys I will take the freedom to quote Gunny:


And after that it ,of course,your table:

I still dont see 9 degree at idle,but that is probably because I cant read maps.FYI my M20 runs best at 13 degree for what it is worth.

You're looking at an 8.5:1 CR M50 on my map. You failed to quote the one with 12 deg of idle advance (also 8.5:1).

The map you quoted from Gunni is a stock motor with a 0.140" thick MLS which drops the engine to like 8.8:1 CR and KILLS the efficiency (kills squish and quench). It is noted that head spacer motors require more timing than low compression motors (with proper pistons vs thick gaskets).

Do more researching!

(If you notice in my table there you will see 8 degrees of timing at 300 kPA vs Otis' 19 - 20 degrees).

I am not sure why you're fighting this - it's dictated by physics lol.

A stock M20 requires much more advance than a stock M50. You can't use head spacer gasket timing maps. Thought that would be painfully obvious?

[bawareca]

Hardly.

There's no use arguing with the clueless. Hopefully the rest of the forum will find this thread useful. The two of you are hopeless. Well, I should say the one is hopeless the other one is intentionally trolling.

Thanks,I knew it's coming.After posted maps in which there is no 9 at idle you are going further with the insults,but looks like it is normal for you.I continue to enjoy your TECH TALK thread :redspot Even in your other map there is no 9* at idle,and I believe it was your primary map.And even if take your time to read your quoted post you will find that you wrote that your timing at full load is what it is because your clutch gave away,so you should open another thread about clutch limited engines:D
If you are tired dont bother to make any more excuses and calls on the laws of physics,I am sure most guys reading that thread know what your next post will be.The only interesting for me is when I will be promoted from hopeless to troll:D

[5mall5nail5]

Thanks,I knew it's coming.After posted maps in which there is no 9 at idle you are going further with the insults,but looks like it is normal for you.I continue to enjoy your TECH TALK thread :redspot Even in your other map there is no 9* at idle,and I believe it was your primary map.And even if take your time to read your quoted post you will find that you wrote that your timing at full load is what it is because your clutch gave away,so you should open another thread about clutch limited engines:D
If you are tired dont bother to make any more excuses and calls on the laws of physics,I am sure most guys reading that thread know what your next post will be.The only interesting for me is when I will be promoted from hopeless to troll:D

I'd post a map from a stock M50 but you still won't get it, whats the point?

Gunni confirmed. Are you going to argue with him too?


Oh... weird...

http://jonkensy.com/gallery/albums/uploads/sparky.jpg

Image Date: 2007-01-05 22:03:17 (no TZ)
Orientation: Normal
Color Space: sRGB
GPS Coordinate: undefined, undefined
Software: Adobe Photoshop CS2 Windows


Date created, so you don't try and say I just made it :rofl

From my 200k mile M50 Non-Vanos MegaSquirt setup w/ stock compression. That's odd... looks like 9 degrees of advance...

[bawareca]

I'd post a map from a stock M50 but you still won't get it, whats the point?

Gunni confirmed. Are you going to argue with him too?


Oh... weird...

http://jonkensy.com/gallery/albums/uploads/sparky.jpg

Image Date: 2007-01-05 22:03:17 (no TZ)
Orientation: Normal
Color Space: sRGB
GPS Coordinate: undefined, undefined
Software: Adobe Photoshop CS2 Windows


Date created, so you don't try and say I just made it :rofl

From my 200k mile M50 Non-Vanos MegaSquirt setup w/ stock compression. That's odd... looks like 9 degrees of advance...
Why should i argue with Gunni?I fully agree with his opinion written a few pages earlier.
If i see a map with 13 degree difference between 2 adjacent fields i would think it should be a shitty tunning,hopeless tuner or all of the above.And that map is what it is not because of the M50 is so efficient,but because your 200 k+ engine is knock(or clutch :D) limited.8 degree @10 psi is not a sign of efficient engine.But at least you are trying to be instrumental now.

[5mall5nail5]

Why should i argue with Gunni?I fully agree with his opinion written a few pages earlier.
If i see a map with 13 degree difference between 2 adjacent fields i would think it should be a shitty tunning,hopeless tuner or all of the above.And that map is what it is not because of the M50 is so efficient,but because your 200 k+ engine is knock(or clutch :D) limited.8 degree @10 psi is not a sign of efficient engine.But at least you are trying to be instrumental now.

Thats a basemap I create for people to get started. The out of boost portion runs the car proper.

I feel bad that you're so lost :(

Run my DTA map in your M20. There's no difference, right?

[gstuning]

Why should i argue with Gunni?I fully agree with his opinion written a few pages earlier.
If i see a map with 13 degree difference between 2 adjacent fields i would think it should be a shitty tunning,hopeless tuner or all of the above.And that map is what it is not because of the M50 is so efficient,but because your 200 k+ engine is knock(or clutch :D) limited.8 degree @10 psi is not a sign of efficient engine.But at least you are trying to be instrumental now.

Ignition timing is not all about hitting MBT all the time, at low loads and engine speeds this can cause a very obnoxious KICK when the throttle is opened up and the torque is quadruppled from say 30kpa slow 1st gear@1750rpm driving to something like 70kpa. Alot of people get improved drivability with less ignition below 2000rpm.

Those ignition values for idle are not the final output value anyway, the VEMS I use adjusts ignition constantly to maintain steady idle, I may want to have the base line a little higher to control the de-acceleration of the engine entering idle, then when its at just above the idle target the ecu pulls out a few degrees and it smoothly comes down to the idle speed . It´s also about emissions as well. 10deg is a general all purpose all around ideal starting point for ignition at idle for a pent roof head. Throttle angle also have ALOT to do with what ignition angle you need for idle, for instance if your missing a ICV but require excellent cold starting behaviour and higher idle speeds like a choke would give, then when it´s warm the ignition is the only thing that can pull the engine speed down to normal idle.

Also please note the rpm scale in Jon´s map, it goes from 1200 to 2000rpm,

Ignition at idle it not really something to discuss in this thread as there are really the most variables in play to affect final timing.

High load (being equal mass flow) is the only comparable situation between two engines, who would also have to have the same compression ratio and plug heat range for absolute ignition values to become comparable. Overall it´s not a excersise in exact scrutineering as what I wrote in my first post are the reasons.

Burn efficiency between the two is negligable btw.

Whoever has the higher turblence intensity after the ignition delay will have a higher flame propogation speed.

[DarkSideofWill]

Define "the same work".



Power output.

Even though BMEP is the same if *TORQUE* output is the same between two different engines of the same output, turbo M20 and turbo M50 at the same torque output are going to be very different engines. The M20 will need more boost to get the same mass flow of mixture into the chambers. Because of the higher boost, it will have higher back pressure and be expending more energy to drive the turbo. The M20 will need a *higher* mass flow in order to achieve the same torque because it's putting more energy into the turbo.

This difference becomes greater at higher RPM and power output as the M20 head becomes more of a restriction. Since the M20's running a higher mass flow at a higher boost and therefore higher temperature, *OF COURSE* it's going to accept less timing...


That's why I asked... "The same work", using the physics definition of work, doesn't make any sense in his argument.

[Quicksilver328i]

Don't you think that variable cam timing and thus variable dynamic compression ratios also play a major factor. The lsx tables I've studied get much less aggressive with a cam, because the dynamic compression ratio is raised.

[BadBoostedBmwM3]

Well, this thread has turned again!!

I'm just going to stay out.

[gstuning]

Even though BMEP is the same if *TORQUE* output is the same between two different engines of the same output, turbo M20 and turbo M50 at the same torque output are going to be very different engines. The M20 will need more boost to get the same mass flow of mixture into the chambers. Because of the higher boost, it will have higher back pressure and be expending more energy to drive the turbo. The M20 will need a *higher* mass flow in order to achieve the same torque because it's putting more energy into the turbo.
.

Thats not exactly correct, you have no idea of the potential or actual backpressure as no mention has been made of turbo manifolds or turbines/turbos or exhaust system sizes. Your assuming.

[DarkSideofWill]

If that can't be assumed, then there is no valid comparison of any kind and this is all masturbation.

[Captain Bondo]

High load (being equal mass flow) is the only comparable situation between two engines, who would also have to have the same compression ratio and plug heat range for absolute ignition values to become comparable. Overall it´s not a excersise in exact scrutineering as what I wrote in my first post are the reasons.
[/B]

The other thing everyone seems to be ignoring, that I alluded to in my first post, is that the burn rate changes SIGNIFICANTLY with AFR.

What this means is that the timing map and fuel map are linked. A certain amount of timing advance is only optimal at a certain AFR.

Even two identical motors with different fuel curves would have distinctly different spark maps (assuming each was optimized).

There are lots of variables. Jon was just trying to present a general concept.
That concept being that an engine with a centered plug will TYPICALLY require less spark advance, which is well proven and valid.

In a general sense, this is worth keeping in mind for the average tuning noob when building their own map or comparing it to others.

Amount of squish area, squish height, port design, AFR, rpm, type of fuel, etc etc also influence the required total advance. Nobody's arguing that I don't think.

A faster burn is typically more efficient because it allows the pressure inside the combustion chamber to be focused to occur when the crank/rod angle are at the optimal position to convert that pressure into crankshaft rotation.

This does ignore the thermal energy aspect but that's another issue.

[BoostedE21]

Man, after reading this thread. I'm so lost on where to even begin to tune an MS. :eyecrazy

Or anything other than my current system.

[5mall5nail5]

Man, after reading this thread. I'm so lost on where to even begin to tune an MS. :eyecrazy

Or anything other than my current system.

It's pretty easy to get roughed in - its just knowing that a 2v BMW head is going to take about 1.6 - 2.0x as much timing advance in general. This is all in general. I recently had someone IM me and say that they put an M20 timing map into an M50 application... so, this was to explain, basically, why that won't work.

[BoostedE21]

It's pretty easy to get roughed in - its just knowing that a 2v BMW head is going to take about 1.6 - 2.0x as much timing advance in general. This is all in general. I recently had someone IM me and say that they put an M20 timing map into an M50 application... so, this was to explain, basically, why that won't work.

Yeah, looking at those maps and tables, no idea what they are or mean. Other than the kpa values and such. My game boy EFI did not prepare me for when I change to MS. :stickoutt

[5mall5nail5]

Yeah, looking at those maps and tables, no idea what they are or mean. Other than the kpa values and such. My game boy EFI did not prepare me for when I change to MS. :stickoutt

Your gameboy ECU is SO confusing. The traditional kPA vs RPM is much more conventional.

Also, when "copying" maps - you MUST ensure that the original poster is running a true, correct crank sensor angle. For instance, if we looked at Jfdmas timing map for his M52 we'd be like wtf this looks like an m30 map. John admits to not really setting the crank angle proper and just "tuned the car for what it wanted" - so, we suspect his crank sensor was off.

We now know an M50 non vanos is around an 84 - 86 crank angle and a VANOS (OBDI, OBDII) is 324 deg.

[Captain Bondo]

eh no need to make it confusing. Pretty much anything will run with an idle advance anywhere from 8-17 degrees, cruise to around 30, 100kpa to around 20, 200kpa around 15. From there you need to drive around with some det cans on.

You should not be beating the car without some manner of knock detection, and preferably on a dyno, anyways.

So an M50 doesn't have a normal 60-2 motronic trigger pattern?

[5mall5nail5]

eh no need to make it confusing. Pretty much anything will run with an idle advance anywhere from 8-17 degrees, cruise to around 30, 100kpa to around 20, 200kpa around 15. From there you need to drive around with some det cans on.

You should not be beating the car without some manner of knock detection, and preferably on a dyno, anyways.

So an M50 doesn't have a normal 60-2 motronic trigger pattern?

All BMW motors other than the M10 have a 60-2 wheel. They moved the gap around.

[BoostedE21]

Your gameboy ECU is SO confusing. The traditional kPA vs RPM is much more conventional.



Really? I found it to be easy to tune. I put all of the values in Excel and saw my "map/tune". The maps posted above, I have no idea what they mean or how you tune it. I guess once I actually have it in my hands I can see and be better educated on it and won't be so intimidated.

[5mall5nail5]

Really? I found it to be easy to tune. I put all of the values in Excel and saw my "map/tune". The maps posted above, I have no idea what they mean or how you tune it. I guess once I actually have it in my hands I can see and be better educated on it and won't be so intimidated.

Your map looks to be some sort of piggy back mode? Like I saw -5, -10, -15 degrees, and then like +5, +12...

That is, if I am reading it right.

[Captain Bondo]

All BMW motors other than the M10 have a 60-2 wheel. They moved the gap around.

Crazy, and good to know. I thought a 60 degree trigger angle was some sort of Bosch "standard" (All Volvo and VAG and SAAB motronic systems I am aware of with 60-2 have a 60 degree trigger angle- whioch makes sense and would be the normal sane thing to do). It would be very "BMW-esque" for them to decide they want to do it their own way, though. Typical. :lol

[5mall5nail5]

Crazy, and good to know. I thought a 60 degree trigger angle was some sort of Bosch "standard" (All Volvo and VAG and SAAB motronic systems I am aware of with 60-2 have a 60 degree trigger angle- whioch makes sense and would be the normal sane thing to do). It would be very "BMW-esque" for them to decide they want to do it their own way, though. Typical. :lol

Well the OBD2 are Siemens units. But, still 60-2 wheels. It also depends on how the ECU counts. Some count from tooth 0 (first missing tooth). Some count from tooth #2 (first present tooth). But, they're different none the less. BMW also changed the cam triggers between various motors.

[good & tight]

Dug up my old M10 spark map. Ran on 93 mixed with 100 octane.

http://i3.photobucket.com/albums/y83/lisaotis/30psi.jpg

[5mall5nail5]

Dug up my old M10 spark map. Ran on 93 mixed with 100 octane.

http://i3.photobucket.com/albums/y83/lisaotis/30psi.jpg

Thanks Otis. Confirms the significant increase over 4v head timing (which I knew, but...).

[BoostedE21]

Your map looks to be some sort of piggy back mode? Like I saw -5, -10, -15 degrees, and then like +5, +12...

That is, if I am reading it right.

You're looking at it right. I set the base timing of the motor (factory settings). Then I adjust the manifold pressure timing...ie -18 degrees of timing at 16psi. There is also fuel RPM and then manifold pressure fuel. MP fuel richens the mixture as your MP raises.

That tune is just my noob tune. Haven't dyno tuned it, but will once we the new motor squared away and install the MS (I'd like to ask for your help if thats okay when the time comes).

[5mall5nail5]

You're looking at it right. I set the base timing of the motor (factory settings). Then I adjust the manifold pressure timing...ie -18 degrees of timing at 16psi. There is also fuel RPM and then manifold pressure fuel. MP fuel richens the mixture as your MP raises.

That tune is just my noob tune. Haven't dyno tuned it, but will once we the new motor squared away and install the MS (I'd like to ask for your help if thats okay when the time comes).

Eek - yeah that's confusing, and hard to "picture".

Sure feel free to hit me up with MS questions. Its been a while but its all the same really.

[BoostedE21]

Eek - yeah that's confusing, and hard to "picture".

Sure feel free to hit me up with MS questions. Its been a while but its all the same really.

Much appreciated!

[NOTORIOUS VR]

so it's clear bawareca was only posting to hear himself talk... WTH kinda garbage was that...

[someguy2800]

one thing to consider is that your not aiming to reach peak cylender pressure at TDC. At TDC there is no leverage on the rod to push on the crankshaft so all the pressure is basically wasted. Many people incorrectly think more timing is allways better until it pings but this is not true because if you spark to early, then your making peak pressure to early when the rod cannot transmit its power to the crank. The result is you pound out the rod bearings and overheat the piston.

I was taught that most motors regardless of design make best power with a peak cylinder pressure around 12-15 degrees after TDC, with the effective power stroke essentially being over at around 20 degrees past TDC. So when you say a motor is running 20 degrees of advance, it really has about 32 degrees of crank rotation to complete the burn vs a motor running 10 degrees of timing which has about 22 degrees of rotation to complete the burn. Bottom line is timing tuning is all about burn rate and dialing in peak cylinder pressure to where the motor can make most efficient use of it.

[bawareca]

one thing to consider is that your not aiming to reach peak cylender pressure at TDC. At TDC there is no leverage on the rod to push on the crankshaft so all the pressure is basically wasted. Many people incorrectly think more timing is allways better until it pings but this is not true because if you spark to early, then your making peak pressure to early when the rod cannot transmit its power to the crank. The result is you pound out the rod bearings and overheat the piston.

I was taught that most motors regardless of design make best power with a peak cylinder pressure around 12-15 degrees after TDC, with the effective power stroke essentially being over at around 20 degrees past TDC. So when you say a motor is running 20 degrees of advance, it really has about 32 degrees of crank rotation to complete the burn vs a motor running 10 degrees of timing which has about 22 degrees of rotation to complete the burn. Bottom line is timing tuning is all about burn rate and dialing in peak cylinder pressure to where the motor can make most efficient use of it.
That is a good point.It also shows that the rod ratio has a lot to do with the timing,i.e. how long the piston has to travel before it reaches the point of maximum leverage.That also explains a lot why there is such a big difference between M20 and M30 timing.
I was looking at old data for euro M20s with ignition distributors.There is roughly 13 degrees difference between M20B20 and M20B20.As they are using the same head and piston design,same intake and exhaust,and very close CR the difference can be explained with the different rod ratio mostly.

[DarkSideofWill]

Many people incorrectly think more timing is allways better until it pings but this is not true

If you can advance ignition timing beyond peak torque without pinging, then you don't have enough boost.

[black bnr32]

This message is hidden because bawareca is on your ignore list (http://forums.bimmerforums.com/forum/profile.php?do=ignorelist)

[Captain Bondo]

That is a good point.It also shows that the rod ratio has a lot to do with the timing,i.e. how long the piston has to travel before it reaches the point of maximum leverage.That also explains a lot why there is such a big difference between M20 and M30 timing.
I was looking at old data for euro M20s with ignition distributors.There is roughly 13 degrees difference between M20B20 and M20B20.As they are using the same head and piston design,same intake and exhaust,and very close CR the difference can be explained with the different rod ratio mostly.

No.

[bawareca]

No.

That is a good point .
So,did you mean that M20B25 and M30B35,as an example, have the same piston speeds,or did you mean that the piston speed is irrelevant to the ignition timing?

[wazzu70]

My assumption would be he knows rod ratio is different and thus piston velocities, but does not think this is the main cause for ignition timing difference.

Bore size is 84mm for the m20 versus 92mm or whatever it is for the M30.

The bore size difference would make a big impact IMO.

[Captain Bondo]

That is a good point .
So,did you mean that M20B25 and M30B35,as an example, have the same piston speeds,or did you mean that the piston speed is irrelevant to the ignition timing?

Rod ratio is largely irrelevant to required timing. The important relationship is that the locus of peak pressure occurs at the appropriate crankshaft angle.
Because a high rod ratio increases piston dwell, one could argue that the effective combustion chamber volume is smaller during combustion and therefore less advance is required, but the influence is marginal.

You need more advance as RPMs increase because the crankshaft is going faster. Everything is referenced to crankshaft angle.

[YellowBed]

Wonder what a pile of junk gen1 Chevy big block requires...


Here's my m30 at 20psi. It was set to about 15* before tuning and it
was a complete turd with that low of advance.



http://img.photobucket.com/albums/v163/glowkid/BMW/M30%20Times/0c8913a3.png

[Lurker27]

You're running 91+methanol, right? Otis runs like 26 degrees on E85 at the top of the cells. I just don't want any M30 bros to see that map and grenade their engine on pump only. btw, what nozzle are you running for meth, I'm setting mine up soon

[YellowBed]

No idea on gph but cooling mist said it was good to 500hp when I bought it 5-6years ago.
The pump is cut back to 85% So probably on the too big side.

[someguy2800]

Bore size is 84mm for the m20 versus 92mm or whatever it is for the M30.



bingo. Plus different cumbustion chamber shape. Rod ratio in my opinion is mostly irreverent and not worth concerning yourself over at this level. I saw a graph once about the difference in piston speed and position between a 5.7 rod and a 6 inch rod and the difference was so miniscule as to make me laugh. There are so much more important things to concern yourself with.

[NOTORIOUS VR]

That is a good point.It also shows that the rod ratio has a lot to do with the timing,i.e. how long the piston has to travel before it reaches the point of maximum leverage.That also explains a lot why there is such a big difference between M20 and M30 timing.
I was looking at old data for euro M20s with ignition distributors.There is roughly 13 degrees difference between M20B20 and M20B20.As they are using the same head and piston design,same intake and exhaust,and very close CR the difference can be explained with the different rod ratio mostly.

:lol

[bawareca]

Everybody has opinion,but there are interesting facts here:

E21 323i ("77-82) distributor no# 0237 302 006
with quoted timing at 22 degs at 1500 rpm
E21 323i late- 0237 302 032 same timing quoted as above
323i 1982-1983 dist no 0237 302 038
19degs at 3000 rpm
323i 1983-1984 dist no 0237 302 040
16 degs at 5000 rpm
323i 1985-1986 dist no 0237 304 025
16 degs at 5000 rpm
320i/6 1982-1983 dist no 0237 302 037
26 degs at 3000rpm
320i/6 dist no 0237 302 039
23 degs at 5000 rpm
320i/6 dist no 0237 304 024
23 degs at 5000 rpm

(from http://sites.google.com/site/e21323i/bmw-m20-engine-ignition-distributor-timing-numbers ,but there are many other sources)

For someone who doesnt know, M20B20 and M20B23 share the same 80 mm bore and the same old and inefficient spherical combustion chamber with slightly domed or flat pistons,same intake,exhaust,etc and a very close CR. There are roughly 7 degree difference between them under high load.Pre 83 are Bosch K-jetronic,84-85 are L-jetronic.
OTOH even the most conservative M50 table shown here runs 20 degree @100 kpa (N/A engine).

[5mall5nail5]

Very few people tune their turbo car at 5000 RPM @ 100 kPA. It's actually very hard to get the engine there.

You're also referencing bosch timing figures to guys who are submitting basemaps. Very few people have standalone tuned NA motors. It also depends where on the 100 kPA line you look.

[bawareca]

Sorry,but the tittle says "Why 2v heads need more advance than 4v heads",and there was discussion about idle timing on the previous page.So what it is?
Timing is timing,no matter if it is controlled via points or MoTec .

[5mall5nail5]

Sorry,but the tittle says "Why 2v heads need more advance than 4v heads",and there was discussion about idle timing on the previous page.So what it is?
Timing is timing,no matter if it is controlled via points or MoTec .

2v heads do need more timing than 4v heads - they have, intrinsically, less efficient combustion chambers. We've been over this already.

You're looking at basemaps for turbo M5x motors and comparing them to NA M20 maps at 5000 RPM and (assuming) 100 kPA. Again, I have yet to tweak the timing on an M50 at 5000 RPM and 100 kPA. I can't get the load to stay there long enough to warrant adjustment from a calculated starting point.

[bawareca]

I am finally out of that discussion,because it is changing the subject with every post :confused However i think there was something interesting for everyone,in different areas ;)



Your comparison with M30 may be correct,but i can assure you that M20 and M30 are different beasts.
And you didnt enlighten us how did you get to the magical number 12.


An M20 is not a different beast. Look at a timing map for each.

How I got to the magical number 12? It's called tuning my friend.

If you really want to prove that you are correct you can multiply your (super conservative) map by 2 and feed it in a M20,or feed Otis's map in M20 :eek:

[5mall5nail5]

I am finally out of that discussion,because it is changing the subject with every post :confused However i think there was something interesting for everyone,in different areas ;)






If you really want to prove that you are correct you can multiply your (super conservative) map by 2 and feed it in a M20,or feed Otis's map in M20 :eek:

You are becoming very irritating the way you quote literally. I've mentioned 1.5 - 2.0x throughout this thread. When an M20 is at 25 degrees under load an M50 may be at 16 degrees... 16 x 1.6 = 25... move on. The subject is not changing you just post so strangely its hard to understand whether or not you are reading the same thread. An M20 takes more time. PERIOD. I don't know what else you want to hear. A half dozen capable people have agreed. The rest of the world is not devastated to find this out but for some reason you're like... fighting it. M20s take more timing than an M50 PERIOD. FACT. The end. The most ridiculous part of your posts in this thread isn't that the rest of us aren't debating whether or not they require more timing or not, but WHY. The first post explains, in the most basic form, why a 2v head requires more than a 4v head. I feel like you're arguing with me that 6 cents is not 6% of a dollar when really we're talking about whether or not sales tax applies.

I get it you disagree with me that's fine, go on your way and do your thing - you're confusing me and surely dudes who are trying to figure this out.

[Captain Bondo]

Timing is timing,no matter if it is controlled via points or MoTec .

Not really. When you're relying on mechanical advance, be it via a vacuum pod and/or centrifugal, you have a fixed timing curve to work with, all you can do is move the whole curve up or down by turning the distributor body.

That data lists the distributor PN precisely because they all have different curves.

Trying to compare them based on a single operating point is meaningless.

[sikdogg]

... I get it you disagree with me that's fine, go on your way and do your thing - you're confusing me and surely dudes who are trying to figure this out.
Amen to that...

[Matt Cramer]

Not really. When you're relying on mechanical advance, be it via a vacuum pod and/or centrifugal, you have a fixed timing curve to work with, all you can do is move the whole curve up or down by turning the distributor body.

That data lists the distributor PN precisely because they all have different curves.

Trying to compare them based on a single operating point is meaningless.

You could potentially tune it by changing the springs in the advance mechanism as well. There's only so many curves you can get this way, but you do have some adjustment. At least, if there is some measure of support from whoever built the distributor...

[Captain Bondo]

You could potentially tune it by changing the springs in the advance mechanism as well. There's only so many curves you can get this way, but you do have some adjustment. At least, if there is some measure of support from whoever built the distributor...

But that's not my point. What I am saying is that you cannot compare two different timing curves based on a SINGLE operating point. :nono

[5mall5nail5]

Yeah a vacuum or spring / fixed distributor can't be compared to an EFI controllable spark. Matt knows this though, he's just sayin'.

[BoostedE21]

Here's my m30 at 20psi. It was set to about 15* before tuning and it
was a complete turd with that low of advance.

http://img.photobucket.com/albums/v163/glowkid/BMW/M30%20Times/0c8913a3.png

A little OT, but can someone please explain to me how to read that map above? I mean I know what it means, X advance at X RPM. But the poster said the timing was at 15*, I don't see where on the table is equals 15*. Unless there is another parameter where you set the amount of retard at a certain MP. (this is how SDS does it, you have base timing then tune the MP ign. ie pull timing under boost).

Sorry for the noobish question. :(

[5mall5nail5]

A little OT, but can someone please explain to me how to read that map above? I mean I know what it means, X advance at X RPM. But the poster said the timing was at 15*, I don't see where on the table is equals 15*. Unless there is another parameter where you set the amount of retard at a certain MP. (this is how SDS does it, you have base timing then tune the MP ign. ie pull timing under boost).

Sorry for the noobish question. :(

That's the issue - whenever you hear someone like bawareca say "See, the engine runs at bawareca at 100 kPA" you have to instantly know that they're just picking one arbitrary point. The timing map on a proper ECU should have 3 scales - RPM, Timing Advance (in degrees, radians, whatever), and a load site. The load site can be throttle % for alpha-N, or it can be +- PSI, or it can be kPA, etc. or it can be lb/min or whatever the unit is you want to represent load.

So, for instance, in Yellowbed's post when he says "it was at 15" we're usually assuming under like peak boost around the torque peak. Like if I were to verbally describe my map I'd say "Yeah around 30 psi I run about 9 - 10 degrees". On my map, at the 300 kPA line around 3000 RPM I am sure its higher than 9, but I can't run the car there and it isn't a real useful figure anyway. It's still vague, but it's a brief way to describe. Factory Motronic 3.1+ ecu's ramp the timing up after 5000 - 5200 RPM or so. They might be 19 - 20 deg in the WOT 5000-5200 range but will ramp up to maybe 24 - 25 degrees by 7000 RPM. Bawareca kept saying "ha, see, the M5x doesn't run less timing!" but that's because he's looking at the ramp up at redline which is almost irrelevant. You really need to look at the timing around 5000 - 5200 RPM to get an idea of how the motors compare.

[Matt Cramer]

A little OT, but can someone please explain to me how to read that map above? I mean I know what it means, X advance at X RPM. But the poster said the timing was at 15*, I don't see where on the table is equals 15*. Unless there is another parameter where you set the amount of retard at a certain MP. (this is how SDS does it, you have base timing then tune the MP ign. ie pull timing under boost).

Sorry for the noobish question. :(

It looks like you're reading this correctly - he's got a single 3D table with MAP (presumably - it could be MAF) on the Y axis and RPM on the X axis. And unless something like an air temperature correction curve that pulls timing when the air heats up too much is kicking in, his engine won't be seeing 15 degrees. I think he was saying he HAD been running 15 degrees under boost, only to find it wasn't enough timing when he tuned it and came up with a table that always gave him more advance.

[5mall5nail5]

It looks like you're reading this correctly - he's got a single 3D table with MAP (presumably - it could be MAF) on the Y axis and RPM on the X axis. And unless something like an air temperature correction curve that pulls timing when the air heats up too much is kicking in, his engine won't be seeing 15 degrees. I think he was saying he HAD been running 15 degrees under boost, only to find it wasn't enough timing when he tuned it and came up with a table that always gave him more advance.

Yep he was implying he had 15 deg and it woke up by putting it up closer to proper timing.

[bawareca]

................

You really need to look at the timing around 5000 - 5200 RPM to get an idea of how the motors compare.

You can talk as much $$hit about me as you like,I dont really care,but ridiculous statements like that come to show that you really know this engine stuff backwards :eek:

I am leaving you to dominate again all the internets and all threads :stickoutt

[BoostedE21]

That's the issue - whenever you hear someone like bawareca say "See, the engine runs at bawareca at 100 kPA" you have to instantly know that they're just picking one arbitrary point. The timing map on a proper ECU should have 3 scales - RPM, Timing Advance (in degrees, radians, whatever), and a load site. The load site can be throttle % for alpha-N, or it can be +- PSI, or it can be kPA, etc. or it can be lb/min or whatever the unit is you want to represent load.

So, for instance, in Yellowbed's post when he says "it was at 15" we're usually assuming under like peak boost around the torque peak. Like if I were to verbally describe my map I'd say "Yeah around 30 psi I run about 9 - 10 degrees". On my map, at the 300 kPA line around 3000 RPM I am sure its higher than 9, but I can't run the car there and it isn't a real useful figure anyway. It's still vague, but it's a brief way to describe. Factory Motronic 3.1+ ecu's ramp the timing up after 5000 - 5200 RPM or so. They might be 19 - 20 deg in the WOT 5000-5200 range but will ramp up to maybe 24 - 25 degrees by 7000 RPM. Bawareca kept saying "ha, see, the M5x doesn't run less timing!" but that's because he's looking at the ramp up at redline which is almost irrelevant. You really need to look at the timing around 5000 - 5200 RPM to get an idea of how the motors compare.


It looks like you're reading this correctly - he's got a single 3D table with MAP (presumably - it could be MAF) on the Y axis and RPM on the X axis. And unless something like an air temperature correction curve that pulls timing when the air heats up too much is kicking in, his engine won't be seeing 15 degrees. I think he was saying he HAD been running 15 degrees under boost, only to find it wasn't enough timing when he tuned it and came up with a table that always gave him more advance.


Yep he was implying he had 15 deg and it woke up by putting it up closer to proper timing.

Okay that makes sense. Thanks for the help!

[5mall5nail5]

You can talk as much $$hit about me as you like,I dont really care,but ridiculous statements like that come to show that you really know this engine stuff backwards :eek:

I am leaving you to dominate again all the internets and all threads :stickoutt

I am not talking "$hit" on you, but I am highlighting to a tuning newbie that you saying an engine "runs at ____ degrees" makes no sense.

Yeah I really suck at this engine thing. My history tuning them and such is pretty terrible.

[Alchemee]

I have some experience with tuning ls motors as I've had 3 different sets of heads on my car na, and now FI.

If we look historically at GM motors starting back in the early 90s with the lt1, they ran best at close to 40 degrees of timing. GM refined the combustion chamber in the lt4 heads and guys were seeing the bets results in the mid to low 30s.

Along comes the ls1 in 97 and now it's 28-30 degrees, then in 2002'ish GM made the ls6 heads which were again an improvement over the ls1's and max timing was lowered to the 23-24 degree range.

I picked up these a few years ago:
http://www.fquick.com/images/vehicles/full/14127324230.jpg?1279502894

http://www.fquick.com/images/vehicles/full/14127324228.jpg?1279502878

They are an aftermarket casting from MAST with revised valve angles and NA I saw the best power at 20-22 degrees of timing. Ask any of the 4-valve mustang guys and they'll tell you that they run in the mid to high teens for timing because the chambers are that efficient.

I think some of the attitude in this thread is coming from confusing efficiency with power or performance. The ls motors were making 330rwhp and juast as much torque from the factory in the late 90s and still got mid to high 20s gas mileage and were actually a low emissions vehicle.

Just interesting food for thought.

[Lurker27]

^ I think that's the nub of it - 2valve guys are taking a FACT of flame propagation and getting their feelings hurt. It's clear to anyone paying attention that it's pretty easy to make huge power on 2v motors, and all the ancillaries (turbo, fueling) are going to consume way more of your attention and money in any build.

[gath]

Bringing this from the dead coz I have a question. What will be needed to run a 2 valve m20 efficiently using a m50 NV engine management. This will include the ECU, harness, injectors, MAF, COP, and all the rest of m50 stuff now hooked onto the m20. How much retard is needed in the m50 maps to make it run well in the m20?

[m20powered]

Interesting thread.
Bringing this from the dead coz I have a question. What will be needed to run a 2 valve m20 efficiently using a m50 NV engine management. This will include the ECU, harness, injectors, MAF, COP, and all the rest of m50 stuff now hooked onto the m20. How much retard is needed in the m50 maps to make it run well in the m20?This could be tricky because Motronic uses airflow as a load index. A stock M20 could flow less air than an M50 in certain RPM ranges (because of lower VE), and this would cause it to calculate MORE advance (because it would be interpreted as lower engine load). I'm going to say that you might need some retard in the 3760-5400RPM rows and possibly around 1500. This is based on looking at M50NV EPROM dumps and my old M20 Megasquirt table.

[gath]

Interesting thread.This could be tricky because Motronic uses airflow as a load index. A stock M20 could flow less air than an M50 in certain RPM ranges (because of lower VE), and this would cause it to calculate MORE advance (because it would be interpreted as lower engine load). I'm going to say that you might need some retard in the 3760-5400RPM rows and possibly around 1500. This is based on looking at M50NV EPROM dumps and my old M20 Megasquirt table.

I am running this setup now and am very impressed with the progress. After starting the vehicle it hunts for idle then settles at 600 rpm, runs a bit rich and CEL comes on after getting to 60 mph.. but drives really well. My only issue is that i have no tuning skills, it is a nightmare..

[Binjammin]

I am running this setup now and am very impressed with the progress. After starting the vehicle it hunts for idle then settles at 600 rpm, runs a bit rich and CEL comes on after getting to 60 mph.. but drives really well. My only issue is that i have no tuning skills, it is a nightmare..

Well, considering the 2v nature of the m20 and the 4v of the m50, your ignition timing alone is going to be a ways off. Also, not sure but someone may be able to confirm if the m20 and m50 have different crank offsets? You'll also be getting a code for a lack of cam sensor, as the m20 doesn't have one of those either...

[e30kid89]

Well, considering the 2v nature of the m20 and the 4v of the m50, your ignition timing alone is going to be a ways off. Also, not sure but someone may be able to confirm if the m20 and m50 have different crank offsets? You'll also be getting a code for a lack of cam sensor, as the m20 doesn't have one of those either...

They have the same trigger offset. I'd say the main issue would be satisfying the cam signal somehow with the m20. Doable but will be challenging

[gath]

Cam sensor is installed on a custom cover plate and seems to be working well. I think the the main issue is the timing/ignition maps.. am running the 403 maps which needs adjusting but that is the challeng.

[5mall5nail5]

An M50 motronic on an M20 would be about 12-15 degrees off (retarded) on average - it'll make very very poor power. Wouldn't recommend it unless you have some way to tune the dme.

[digger]

most of the reason why 4V makes more power than 2V is in valve curtain area and absolute flow potential rather than combustion efficiency. this allows use of shorter duration and potentially wider lobe centre cams which tend to broaden the power curve. plus modern 4V engines have other bags of tracks like vanos and so forth that also allow use of smaller cams

when you look at custom design race heads of 2V nature they give nothing up to the 4V in peak hp and peak torque which is evident in the BMEP they are achieving, though wont have the broadness in the power curve. this is not much use to any of us when you start off with a OEM casting decades old where power and torque weren't the primary focus but nevertheless it should be noted.

saying that 4V is more efficient than 2V is not absolute IMO, it certainly applies to OEM castings but is not an absolute

in addition to this most aftermarket m20 pistons lose the good features of the stock pistons killing the squish and hardly anyone does a good job with the cylinder head. there are a couple of NA m20 in the range 290-350rwhp from 2.9 and 2.8L respectively you dont see many US spec S50 or M50/52 near there.....

[bawareca]

in addition to this most aftermarket m20 pistons lose the good features of the stock pistons killing the squish and hardly anyone does a good job with the cylinder head. .
It is amazing how no one aftermarket M20 pistons "engineer" cares about the squish,but no one cares about M20 anyway and everything is good in the world.

[Quicksilver328i]

It is amazing how no one aftermarket M20 pistons "engineer" cares about the squish,but no one cares about M20 anyway and everything is good in the world.It is amazing how few aftermarket pistons are designed with combustion chamber shape in mind at all.

There are a lot of lessons that can be taught by looking at the shapes of OE parts that aren't.

One of my favorite "puzzles" to throw people is how "messed up" looking an LSx combustion chamber is compared with most modern DOHC combustion chambers, yet they still seem to work incredibly well in a variety of environments still...

[digger]

It is amazing how no one aftermarket M20 pistons "engineer" cares about the squish,but no one cares about M20 anyway and everything is good in the world.

you can get them by JE and even ross do them now, all of them would do it if you sent them a mould of the chamber and a sample piston but most customers seem to like any piston as long as it is shiny, forged and CNC'd because it must be good.
the ones that use it seem to be better overall for it and have less tune issues......

[DarkSideofWill]

It is amazing how few aftermarket pistons are designed with combustion chamber shape in mind at all.

There are a lot of lessons that can be taught by looking at the shapes of OE parts that aren't.

One of my favorite "puzzles" to throw people is how "messed up" looking an LSx combustion chamber is compared with most modern DOHC combustion chambers, yet they still seem to work incredibly well in a variety of environments still...

If you know what you're looking at, the LS chamber doesn't look messed up at all... And has WAY more quench pad area than any 4V chamber.

[Quicksilver328i]

If you know what you're looking at, the LS chamber doesn't look messed up at all... And has WAY more quench pad area than any 4V chamber.
Exactly, which is why its fun to show it to people who don't know what they're looking at

[wazzu70]

Want to post up a picture of the mentioned LS chamber and piston?

[Quicksilver328i]

Alchemee posted some examples of a slightly modified head. A lot of the pistons are flat top, some of the lower compression motors had a dish top.

http://www.ssrfanatic.com/forum/attachments/f5/48247d1207797952-ssr-ls2-head-cam-swap-img_0760.jpg
http://i1000.photobucket.com/albums/af127/1nasty86/Mobile%20Uploads/2011-12-17_093651.jpg

Random googled photos of LS2 parts for example.

I particularly love the spark plug placement.

[SLEEPYDUB]

Going to resurrect this thread for some of you.

I have an M20 with a B27 bottom end, and the 885 head. Would this combo require even more timing then a normal B25 head/bottom? I am running what seems to be a lot of timing, even in boost up to 20psi. So lets say where a B25 requires 23* of timing, would the b27 bottom require even more? If so, how much?

[digger]

IMO with lower compression and lack on mixture motion due to mismatch in piston and head yes it would burn a little slower and require a little more advance