Page 5 of 7 FirstFirst 1234567 LastLast
Results 101 to 125 of 154

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

  1. #101
    Join Date
    Mar 2003
    Location
    Orange County, So CA
    Posts
    5,378
    My Cars
    Turbo E21,12 WRX,03 S2K
    Quote Originally Posted by 5mall5nail5 View Post
    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).

    E21 LEGION


    Crypto success: http://brief.watchersfrontline.com/SHV

  2. #102
    Join Date
    Sep 2002
    Location
    USA
    Posts
    45,770
    My Cars
    BMWs
    Quote Originally Posted by BoostedE21 View Post
    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.

  3. #103
    Join Date
    Mar 2003
    Location
    Orange County, So CA
    Posts
    5,378
    My Cars
    Turbo E21,12 WRX,03 S2K
    Quote Originally Posted by 5mall5nail5 View Post
    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!

    E21 LEGION


    Crypto success: http://brief.watchersfrontline.com/SHV

  4. #104
    Join Date
    Oct 2006
    Location
    Toronto, Canada
    Posts
    3,375
    My Cars
    E36 Turbo
    so it's clear bawareca was only posting to hear himself talk... WTH kinda garbage was that...

  5. #105
    Join Date
    Apr 2006
    Location
    Minnesota eh?
    Posts
    6,155
    My Cars
    86 325es
    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.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  6. #106
    Join Date
    Jul 2005
    Location
    Mission Hills , CA
    Posts
    2,490
    My Cars
    X535D 323iS Z4 i3
    Quote Originally Posted by someguy2800 View Post
    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.

  7. #107
    Join Date
    Jan 2009
    Location
    In the Darkness, where fear and knowing are one
    Posts
    700
    My Cars
    1987 Fiero GT
    Quote Originally Posted by someguy2800 View Post
    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.

  8. #108
    Join Date
    Jul 2008
    Location
    Saskatoon, SK, Canada
    Posts
    2,678
    My Cars
    m3, gtr
    This message is hidden because bawareca is on your ignore list

  9. #109
    Join Date
    May 2009
    Location
    Vancouver, BC, Canada
    Posts
    453
    My Cars
    '89 535i/5 speed
    Quote Originally Posted by bawareca View Post
    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.

  10. #110
    Join Date
    Jul 2005
    Location
    Mission Hills , CA
    Posts
    2,490
    My Cars
    X535D 323iS Z4 i3
    Quote Originally Posted by Captain Bondo View Post
    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?

  11. #111
    Join Date
    Sep 2005
    Location
    Bellingham, WA
    Posts
    3,372
    My Cars
    e30
    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.
    -Nick
    91 E30 M42 on VEMS

    Turbo Camshaft Thread

  12. #112
    Join Date
    May 2009
    Location
    Vancouver, BC, Canada
    Posts
    453
    My Cars
    '89 535i/5 speed
    Quote Originally Posted by bawareca View Post
    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.

  13. #113
    Join Date
    Apr 2006
    Location
    USA
    Posts
    870
    My Cars
    E30 m30 turbo
    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.



    Last edited by YellowBed; 03-20-2012 at 11:20 PM.

  14. #114
    Join Date
    Aug 2004
    Location
    Delaware
    Posts
    574
    My Cars
    E30 M30 Turbo
    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

  15. #115
    Join Date
    Apr 2006
    Location
    USA
    Posts
    870
    My Cars
    E30 m30 turbo
    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.

  16. #116
    Join Date
    Apr 2006
    Location
    Minnesota eh?
    Posts
    6,155
    My Cars
    86 325es
    Quote Originally Posted by wazzu70 View Post
    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.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  17. #117
    Join Date
    Oct 2006
    Location
    Toronto, Canada
    Posts
    3,375
    My Cars
    E36 Turbo
    Quote Originally Posted by bawareca View Post
    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.

  18. #118
    Join Date
    Jul 2005
    Location
    Mission Hills , CA
    Posts
    2,490
    My Cars
    X535D 323iS Z4 i3
    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...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).
    Last edited by bawareca; 03-21-2012 at 11:21 AM.

  19. #119
    Join Date
    Sep 2002
    Location
    USA
    Posts
    45,770
    My Cars
    BMWs
    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.

  20. #120
    Join Date
    Jul 2005
    Location
    Mission Hills , CA
    Posts
    2,490
    My Cars
    X535D 323iS Z4 i3
    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 .

  21. #121
    Join Date
    Sep 2002
    Location
    USA
    Posts
    45,770
    My Cars
    BMWs
    Quote Originally Posted by bawareca View Post
    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.
    Last edited by 5mall5nail5; 03-21-2012 at 12:45 PM.

  22. #122
    Join Date
    Jul 2005
    Location
    Mission Hills , CA
    Posts
    2,490
    My Cars
    X535D 323iS Z4 i3
    I am finally out of that discussion,because it is changing the subject with every post However i think there was something interesting for everyone,in different areas


    Quote Originally Posted by bawareca View Post
    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.
    Quote Originally Posted by 5mall5nail5 View Post
    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

  23. #123
    Join Date
    Sep 2002
    Location
    USA
    Posts
    45,770
    My Cars
    BMWs
    Quote Originally Posted by bawareca View Post
    I am finally out of that discussion,because it is changing the subject with every post 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
    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.
    Last edited by 5mall5nail5; 03-21-2012 at 02:10 PM.

  24. #124
    Join Date
    May 2009
    Location
    Vancouver, BC, Canada
    Posts
    453
    My Cars
    '89 535i/5 speed
    Quote Originally Posted by bawareca View Post
    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.

  25. #125
    Join Date
    Oct 2008
    Location
    SoCal
    Posts
    901
    My Cars
    '97 328i
    Quote Originally Posted by 5mall5nail5 View Post
    ... 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...

Page 5 of 7 FirstFirst 1234567 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •