Steep drop on dyno???

[S--K]

Just wondering if anyone knows why the M motor's torque curve dives so much ( on the dyno graph ) after 5000 RPM??

I've seen some dyno's of VTEC motors that are
flat all the way to redline.

Is there any way to maintain our torque curve
like that ?

[V Shah]

He he, you could just get a supercharger... Dyno (http://fp.geocities.com/bandbauto/m3_dyno.jpg)

I believe the drop on stock cars is because of the VANOS. Please correct me if I'm wrong.

[Kevlar]

after 5250 torque is bound to go down because of the function used to calculate it.

refering to the VTEC engines... if you look at the engines without using the cam profile, you'll see that they start losing power very early. However, since they change cam profiles at 5000rpm, they use a more (F1 like) cam profile for higher engine speeds.

[m3fanatic97]

By the nature of the inline 6, It will peak (torque-wise) earlier than say a free revving v6.

[S--K]

It's the reverse Kevlar. HP is calculate right?

HP = (Torque x RPM) / 5250

I would imagine torque to be the true representative
of how the much the engine pulls at any point on the
dyno graph.

[stimpee]

To go out on a limb and correct Kevlar,

Torque is the measured quantity. A dyno measures torque vs. time and/or rpm. Horsepower is simply a human created calculated function of torque and rpm

hp = torque * rpm/5252

The curves always cross at 5252, but the torque falloff is purely a function of the way the engine is "tuned".

Mr. Pee

[S--K]

Hey,

M3fanatic, please enlighten as to what quality of the
inline 6 causes the dip in torque? I really don't know.

Why is the V6 free-er revving? I was guessing that
it had something to do with the M3's intake also.

Thanks.

[S--K]

Dang, Vshah that's a nice flat torque curve!!!!!!


Do you know a site that has some other dyno
graph examples???

The turbo graph's on Kevlar site show that the
turbo car's fade more in the upper end of the RPM
range, but they more than make up for this my
still making soooo much torque in these RPM ranges.

[Kevlar]

yeah... that's the formula I was talking about... i couldn't think of it off the top of my head... I was kinda grasping at straws.

[Bob ///M3]

http://www.bonnevillemotorwerks.com/images/e36m3-dyno.gif

Jim Conforti's stock vs modified HP & Torque Table (http://www.bonnevillemotorwerks.com/e36m3-dyno.html)

Torque and horsepower curves are affected by many things. As you can see from the above graph which compares a stock engine with one that has altered ignition and fuel maps, the enhanced performance software not only gives the engine increased horsepower and torque but it actually alters the curves somewhat. Other things that affect the curves are camshaft timing, valve lift duration, piston stroke, air intake, fuel delivery, etc., etc.

I think the M3's engine has a very flat torque curve and one that is very nice for a performance street car. Having the torque peak at a much higher level would require redesigning major engine components. Of course raising the torque peak real high in the rpm range would offer very little low and mid-range torque. Unfortunately, that's the tradeoff. We can't have high torque values in the low-range, mid-range and high-range! The closest engine design that offers such an example of this is the Wankel rotary engine (13B) that Mazda used in their RX7.

I hope the curves help you.
http://bobcrews.homestead.com/files/Tach_Rev_URL.gif

Bob <font color="1E90FF">/</font><font color="7D26CD">/</font><font color="red">/</font><b><font color="gray">M3</font></b>

[S--K]

Bob, Awesome cartoon!!!

Thanks for the info!!!

I'm curious though are the J.C. gains for real? What
was it like 40 HP gains and 30 ft/lb of torque?

If that's true, I'm sending my computer in ASAP!!!!

[S--K]

OHH, I also wanted to say that I wasn't asking to
raise the peak torque to a higher RPM level -- I really
wanted to find a way for the dip starting at 5000 RPM
to be minimized. The torque seems to drop about
25 ft/lbs from 5000 to 6500 RPM (it drops from about 200 to 175) -- if you could find a way to keep the torque around 200 from 5K to 6.5K you have upped your HP and pulling power without really increasing you peak torque and you also have a flatter torque curve in the process.

Thanks.

[S--K]

Ohh, just realized something. Do some vendors
offer the JC ECU reprogramming for OBDII cars, if so
is there a list somewhere or should I just email
JC?

[RS]

ya, somewhere I heard "horsepower is what you brag about, but torque is what you feel" and I think one of the reasons the torque falls off a bit is due to the intake system being tuned for a lower rpm punch. I got a chance to play with a dyno and a 600cc F2 engine for a year when in school working on the formula SAE team and the difference that intake runner lengths have on torque generated at a given rpm is dramatic (with everything else being the same). When the intake valve closes and the air/fuel that was rushing in, abruptly stops, it generates a pressure wave that travels up the intake runner and when the pulse hits the runner opening leading into the manifold it is sort of reflected back (compression wave becomes refraction wave..I think). The reflected back portion now has a little bit of a positive pressure charge to it and when the intake valve opens at the time when the charge arrives, it forces air/fuel into the cylinder (with the speed of sound being so high, the wave actually bounces back and forth many times between intake valve openings). The timing on that positive charge is based on the length of the runner so by playing with that you can really change the engine characteristics. Obviously, thats why superchargers are so nice cause they are always stuffing the air/fuel into the cylinder, and I guess thats why the curve is so flat. So the longer the runners, the more the engine is tuned for lower rpm grunt. Thats why you see newer cars now with dual length intake runner systems and why Formula 1 engines actually have a mechanisim that telescopes their intake runners as a function of rpm.

So the little rice cake engines (actually honda engines are great :) ) have shorter runners and since they redline so high, they take advantage of lower gearing to put more torque to the ground for a longer time as the engine spools up........Thats just one piece of the pie....as Bob/// shows with his charts you can do alot with ignition/fuel maps too, but the "hump" at ~3800 is kinda still there until you start forcing air in.......

Bob///, is that dyno difference just a result in "sharking" it + a CAI or something...man thats a big increase!

[S--K]

Thanks, great technical explanation.

One question though is why is the torque curve on the
S.C. flatter than that of the Turbo? (See Kevlar's Dyno
charts at www.activeautowerke.com/dyno)

[RS]

I think the reason the torque curve is so flat on a S/C system is that you dont have to worry about lag. So with the belt driven S/C system you have a compressor that is plenty big to pump enough air/fuel up to redline and its directly rpm specific. With the turbos spooled up by exhaust gases, that alone is kinda non-linear and since you dont want these blades taking all day to spin up, its sized a little smaller and I dont think it can pump as much air/fuel at higher rpm. The little 1.8T from the audi/vw is a good example. With 5 valves per cylinder, that little sucker is very free breathing and the little turbo does wonders at low rpm, but you get it past 5500 and it starts to die....but then theres not that much lag vs bigger turbo, more lag.....so its a trade off....
Also, S/C's take quite a bit more hp to make hp (spinning that belt driven pump) versus a turbo system (kinda free hot exhaust gases)

it must be a blast to have a turbo on an m :)

[C.Yang]

Torque is basically what makes your car "feel" fast, but HP is what determines whether your car is fast (subject to discussion). HP is torqueXrpm/constant. So the higher the RPM, the higher the HP, and higher the torque, higher the HP. Torque is the actually energy created by your engine. This is transferred to the wheels in the form of turning power. Horsepower helps put torque and rpm into a number which tells how fast a car can go. The reason why RPM's is important in determining many cars ability to accelerate fast is gearing. Honestly, i forgot the reasoning, but I think it has something to do with gearing. An example showing why RPM's is important is looking at say tugboats. Those boats have tons of torque, but no HP, because they don't have the ability to get the RPM's real high They have a lot of torque, but relatively low HP. Torque is the actual energy, but doesn't say how it is applied. You can have tons of torque, with low HP, but not vice versa. OH, and this is my 100th post. Lets see if ive Mpowered with the Mpower now

[C.Yang]

just a senior member........

[RS]

so when does junior status turn into senior???

actually torque is rotational force, and horsepower is a unit of energy. Horsepower is the rate at which work (force * distance) is done. So ya, hp is a good indication that your car is fast because it means that it can do a lot of work at a high rate and its easy to quote, instead of telling someone that my engine has x torque and I can rev it to x rpm and ..blah..blah. And the gearing thing is true...so, like a semi (low hp, high torque) for example, if those things could rev higher (say 6000) than their ~2500 redline, the ~1400 ft-lbs of torque they put could be run through gears lower than they already are and give better accelleration as the engine revs up. And you can have high hp, low torque engines, you just need to spin it fast...rotary engines, or jet turbine engines for example.

[V Shah]

Originally posted by RS
so when does junior status turn into senior???

I believe you turn into a "Member" after 30 posts and a "Senior Member" after 100 posts.

[S--K]

C.yang you said:

"So the higher the RPM, the higher the HP, and higher the torque, higher the HP."

Higher RPM doesn't equal higher torque in the M motor, but higher RPM does equal higher horsepower(generally). In essence what I was asking was how to better maintain the torque of the M motor from the 5K to 6.5 K RPM (this is where it drops from ~200 to 175
foot pounds). Imagine if you had 200 ft lbs of torque
at 6K RPM you have this much HP:

HP = (200 x 6000) / 5252

HP = 228.5

vs.


HP = (175 x 6000) / 5252

HP = 200

28 HP would mean about 4 mph faster in your quarter mile times.

[Bob ///M3]

There's been a certain amount of discussion, in this and other forums about the concepts of horsepower and torque, how they relate to each other and how they apply in terms of automobile performance. I have observed that although nearly everyone participating has a passion for automobiles there is a huge variance in knowledge. It's clear that a bunch of folks have strong opinions (about this topic, and other things) but that has generally led to more heat than light. This is meant to be a primer on the subject, which may lead to serious discussion that fleshes out this and other subtopics that will inevitably need to be addressed.

OK. Here's the deal, in moderately plain english.


Force, Work and Time:

If you have a one pound weight bolted to the floor and try to lift it with one pound of force (or 10, or 50 pounds) you will have applied force and exerted energy but no work will have been done. If you unbolt the weight and apply a force sufficient to lift the weight one foot then one foot pound of work will have been done. If that event takes a minute to accomplish then you will be doing work at the rate of one foot pound per minute. If it takes one second to accomplish the task then work will be done at the rate of 60 foot pounds per minute, and so on.

In order to apply these measurements to automobiles and their performance (whether you're speaking of torque, horsepower, newton meters, watts, or any other terms), you need to address the three variables of force, work and time.

Awhile back, a gentleman by the name of Watt (the same gent who did all that neat stuff with steam engines) made some observations and concluded that the average horse of the time could lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 foot pounds per second, or 33,000 foot pounds per minute, for an eight hour shift, more or less. He then published those observations and stated that 33,000 foot pounds per minute of work was equivalent to the power of one horse, or one horsepower.

Everybody else said OK!

For purposes of this discussion we need to measure units of force from rotating objects such as crankshafts so we'll use terms which define a *twisting* force, such as foot pounds of torque. A foot pound of torque is the twisting force necessary to support a one pound weight on a weightless horizontal bar one foot from the fulcrum.

Now, it's important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynomometer) is torque, expressed in foot pounds (in the U.S.), and then we *calculate* actual horsepower by converting the twisting force of torque into the work units of horsepower.

Visualize that one pound weight we mentioned, one foot from the fulcrum on its weightless bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (Pi * a two foot circle), and incidently, we have done 6.2832 foot pounds of work.

OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per revolution of that weight into 33,000 foot pounds, we come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 foot pounds per minute of work and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it's the equivalent of 1/2 horsepower (16,500 foot pounds per minute) and so on. Therefore, the following formula applies for calculating horsepower from a torque measurement:


Torque * RPM

Horsepower = ------------

5252


This is not a debatable item. It's the way it's done. Period.

Torque:

First of all, from a driver's perspective "torque", to use the vernacular, RULES! Any given car (in any given gear) will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.

In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb however, until well past the torque peak and will continue to rise as engine speed climbs until the torque curve really begins to plummet faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*!


You don't believe all this?

Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear and punch it. Notice the belt in the back? Now take it to the power peak and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now?


The Case For Horsepower:

OK. If torque is so all-fired important, why do we care about horsepower?

Because, "It is better to make torque at high rpm than at low rpm because you can take advantage of *gearing*. Ah, gearing!

For an extreme example of this I'll leave carland for a moment and describe an example using a waterwheel. This is a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which is connected to the works inside a flour mill. Working some things out from what the people in the mill said, it was determined that the wheel typically generated about 2600(!) foot pounds of torque. Wow! Clocking its speed and determining that it was rotating at about 12 rpm, if we hooked that wheel to, say the drivewheels of a car, that car would go from zero to twelve rpm in a flash and the waterwheel would hardly notice!

On the other hand, twelve rpm of the drive-wheels is around one mph for the average car and in order to go faster we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us:

6 HP.

Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited.


At The Dragstrip:

Okay, back to carland and some examples of how horsepower makes a major difference in how fast a car can accelerate in spite of what torque on your backside tells you.

A very good example would be to compare a LT1 Corvette with the last of the L98 Vettes. Figures as follows:


Engine Peak HP @ RPM Peak Torque @ RPM

------ ------------- -----------------

L98 250 @ 4000 340 @ 3200

LT1 300 @ 5000 340 @ 3600


The cars are geared identically, and car weights are within a few pounds, so it's a good comparison.

First, each car will push you back in the seat (the fun factor) with the same authority...at least at or near peak torque in each gear. One will tend to *feel* about as fast as the other to the driver but the LT1 will actually be significantly faster than the L98 even though it won't pull any harder. If we mess about with the formula, we can begin to discover exactly *why* the LT1 is faster. Here's another slice at that formula:


Horsepower * 5252

Torque = -----------------

RPM


If we plug some numbers in we can see that the L98 is making 328 foot pounds of torque at its power peak (250 hp @ 4000), and we can infer that it cannot be making any more than 263 pound feet of torque at 5000 rpm, or it would be making more than 250 hp at that engine speed and would be so rated. In actuality, the L98 is probably making no more than around 210 pound feet or so at 5000 rpm and anybody who owns one would shift it at around 46-4700 rpm because more torque is available at the drive wheels in the NEXT higher gear at that point.

On the other hand, the LT1 is fairly happy making 315 pound feet at 5000 rpm and is happy right up to its mid-5,000 rpm redline.

So, in a drag race, the cars would launch more or less together. The L98 might have a slight advantage due to its peak torque occuring a little earlier in the rev range, but that is debatable since the LT1 has a wider and flatter curve (again pretty much by definition, looking at the figures). From somewhere in the mid range and up however, the LT1 would begin to pull away. Where the L98 has to shift to second (and throw away torque multiplication for speed), the LT1 still has around another 1000 rpm to go in first and thus begins to widen its lead...more and more as the speeds climb. As long as the revs are high, the LT1, by definition, has an advantage.

Another example would be the LT1 against the ZR-1. Same deal, only in reverse. The ZR-1 actually pulls a little harder than the LT1 although its torque advantage is softened somewhat by its extra weight. The real advantage however, is that the ZR-1 has another 1500 rpm in hand at the point where the LT1 "must" shift.

There are numerous examples of this phenomenon. The Integra GS-R for instance is faster than the garden variety Integra not because it pulls particularly harder (it doesn't), but because it pulls *longer*. It doesn't feel particularly faster, but it is.

A final example of this requires your imagination. Figure that we can tweak an LT1 engine so that it still makes peak torque of 340 foot pounds at 3600 rpm but instead of the curve dropping off to 315 pound feet at 5000 we extend the torque curve so much that it doesn't fall off to 315 pound feet until 15000 rpm!!! Okay, so we'd need to have virtually all the moving parts made out of some space-age exotic material...and use some sort of turbocharging on demand that would make enough high-rpm boost to keep the curve from falling...hey, bear with me.

If you raced a stock LT1 against this car, they would launch together, but somewhere around the 60 foot point the stocker would begin to fade and would have to grab second gear shortly thereafter. Not long after that you'd see in your mirror that the stocker has grabbed third and not too long after that, it would get fourth but you really wouldn't be able to see that due to the distance between you (as you crossed the finish line), *still in first gear*, and pulling like crazy!

I've got a computer program that models an LT1 Vette in a quarter mile pass, and it predicts a 13.38 second ET, at 104.5 mph. That's pretty close (actually a tiny bit conservative) to what a stock LT1 can do at 100% air density at a high traction drag strip, being powershifted. However, the modified car, while belting the driver in the back no harder than the stocker (at peak torque) does an 11.96, at 135.1 mph all in first gear, of course! It doesn't pull any harder, but it sure as hell pulls longer! It's also making *900* hp at 15,000 rpm. The formula is fact!

Of course, folks who are knowledgeable about drag racing are now openly snickering because they've read the preceeding paragraph and it occurs to them that any self respecting car that can get to 135 mph in a quarter mile will just naturally be doing this in less than ten seconds. Well, of course that's true, but I remind these same folks that any self-respecting engine that propels any car into the nine second bracket is also making a whole bunch more than 340 foot pounds of torque too.

That does bring up another point, though. Essentially, a more "real" car running 135 mph in a quarter mile might be making 700-800 foot pounds of torque and thus it would pull a whole bunch harder than my paper tiger would. It would need slicks and other modifications in order to turn that torque into forward motion but it would also get from here to way over there a bunch quicker.

On the other hand, as long as we're making quarter mile passes with fantasy engines, if we put a 10.35:1 final-drive gear (instead of like a 3.23), with slicks and other chassis mods, we'd be in the nines just as easily and thus save face. The mechanical advantage of such a non-sensible rear gear would allow our combination to pull just as hard, plus we'd get to do all that gear banging and such that real racers do, and finish in fourth gear, as God intends drag racers to do!

The only modification to the preceeding paragraph would be the polar moments of inertia (flywheel effect) argument brought about by such a "stiff" or low rear (final drive) gear and that argument is outside of the scope of this already massive document.


At The Bonneville Salt Flats:

Looking at "top speed", horsepower wins, in the sense that making more torque at high rpm means you can use a stiffer (lower) gear for any given car speed and thus have more effective torque *AT THE DRIVE WHEELS*.

Finally, operating at the power peak means you are doing the absolute best you can at any given car speed, thus measuring torque at the drive wheels. I know I said that acceleration follows the torque curve in any given gear, but if you factor in gearing vs car speed, the power peak is *it*. An example. If you take our same car engine up to its torque peak in a gear, it will generate some level of torque (foot pounds times "whatever overall gearing") at the drive wheels, which is the best it will do in that gear (meaning, that's where it is pulling hardest in that gear).

Any rpm (other than the power peak) at a given car speed will net you a lower torque value at the drive wheels. This would be true of any car on the planet, so, theoretical "best" top speed will always occur when a given vehicle is operating at its power peak.


"Modernizing" The 18th Century:

Okay. for the final-final point! What if we ditched that water wheel and bolted an LT1 in its place? Now, no LT1 is going to be making over 2600 foot pounds of torque (except possibly for a single, glorious instant, running on nitromethane), but assuming we needed 12 rpm for an input to the mill, we could run the LT1 at 5000 rpm (where it's making 315 foot pounds of torque) and gear it down to a 12 rpm output. Result? We'd have over *131,000* foot pounds of torque to play with. We could probably twist the whole flour mill around the input shaft, if we needed to! The formula is fact!

The Only Thing You Really Need to Know...repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*. Ah, and you ask what the best shift points are! And, question whether being able to shift at a higher rpm reduces the rear wheel torque loss. And, if just maybe using performance enhancing software helps in areas not seen on a dynometer!

Bob <font color="1E90FF">/</font><font color="7D26CD">/</font><font color="red">/</font><b><font color="gray">M3</font></b>

[RS]

uhhhh, what he said :)

damn, now thats a response...

nicely put, thanks Bob

[S--K]

Thanks Bob, great technical response. You've expounded on what I've been asking -- how to
maintain the M3 torque from 5K to 6.5K RPM??

By the way did you get a chance to read my questions regarding the JC chip??? Please answer if you can.

Thanks!!

[Bob ///M3]

S--K, I think the Jim Conforti performance software is indeed for real! I question the amount of gain in torque and horsepower that I see published however it stands to reason there "must" be some.

It is important to note that even "if" there was absolutely no gain in torque or horsepower the ability to shift at 500 rpms higher is a tremendous performance advantage. The results are staggering!

With a completely stock engine you have a big mis-match of driveshaft torque depending on "what gear you are shifting into" based on the transmission's gearing.

The mis-match for a stock engine can be seen in the following data:

Best shift point for the 1-2 shift is 6500 with a LOSS of 242 Lb/Ft of torque.

Best shift point for the 2-3 shift is 6500 with a LOSS of 111 Lb/Ft of torque.

Best shift point for the 3-4 shift is 6500 with a LOSS of 43 Lb/Ft of torque.

Best shift point for the 4-5 shift is 6500 with a LOSS of 43 Lb/Ft of torque.


Now compare the above "stock" engine driveshaft torque mis-match with the following figures that represent the exact same engine (torque and horsepower) except the rev limit has been increased by 500 rpm!

Best shift point for the 1-2 shift is 7000 with a LOSS of 61 Lb/Ft of torque.

Best shift point for the 2-3 shift is 7000 with a LOSS of 4 Lb/Ft of torque.

Best shift point for the 3-4 shift is 7000 with a GAIN of 29 Lb/Ft of torque.

Best shift point for the 4-5 shift is 6500 with a GAIN of 29 Lb/Ft of torque.

As you can see, just raising the rev limit by 500 rpms without any engine gains allows a much better driveshaft torque match. This can be noted by the much lower mis-match figures (which are better) at each shift...in particular for the 1st to 2nd and 2nd to 3rd gear shifts; 242 lb/ft vs. 61 lb/ft and 111 lb/ft vs. 4 lb/ft respectively. It must be noted that the closer to "zero" (0) the driveshaft torque match is, the better...as it can be either a "loss" or a "gain". Perfect, of course, would be zero but the smallest amount of loss or gain, the better!

Now then, "if" the performance software does actually increase the engine's torque and/or horsepower then the car's performance is even that much better. And, as I have already stated, I do indeed believe there is an increase in engine torque and horsepower.

Could I "feel" the difference? Oh yes, I could! But then again some people are more sensitive to this sort of thing. Some people couldn't feel the difference in their car's performance if two 250 lbs guys jumped into the back seat adding 500 lbs to the weight of their car!

Then again, it has been noted that after adding the performance software there was no increase seen on a dyno! I believe testing differences with a OBDII engine is next to impossible due to the so many different (and complex) sensors feeding signals to the engine management unit.

Other than increasing the rev limit by 500 rpm (with the already mentioned advantages) the performance software also alters the ignition and fuel maps which "allows" the engine to take advantage of them but only if the conditions are "right"! "Right" meaning that on those maps (ignition and fuel) there is altered (for the better) ignition and fuel delivery "if" the air temperature is right, engine temperature is right, fuel octane is right, etc. ,etc. You may ask if there is ever a time when the better maps are indeed used; and my answer is yes, I think so depending on "conditions.

Can I feel the difference? Yes, most all the time...depending on "conditions"!

Would I buy it again? Yes!

Would I buy it again if I was told there would be no engine torque or horsepower gain? Yes, because as I've already explained just raising the rev limit alone increases the "car's" performance by reducing the driveshaft torque loss.

Bob <font color="1E90FF">/</font><font color="7D26CD">/</font><font color="red">/</font><b><font color="gray">M3</font></b>



Originally posted by S--K
Bob, Awesome cartoon!!!

Thanks for the info!!!

I'm curious though are the J.C. gains for real? What
was it like 40 HP gains and 30 ft/lb of torque?

If that's true, I'm sending my computer in ASAP!!!!

[Zippy M3]

Bob ///M3,

This is your boss...back to work! Hahahaha.

Great explanation!

[gerry_miranda]

Question about Dyno's on DME upgrades.

How come some people are seeing gains, but a lot are seeing no gains on the DYNO? This has been attributed to the DIFFICULTY in accurately testing OBD2 cars.

When I had my DME upgraded the dyno did not see any changes.


BUT....if the OBD2 dyno issues are the cause, how come all the DYNO results I here regarding CAI on ODB2 are positive gains. I have never heard any one say, "I put in a CAI and saw no gains"?

[RS]

ooops.... earlier I said that horsepower is a unit of energy....I meant that it is a unit of power, or time rate of work/energy done....just wanted to clear that up.

Another little way of looking at it: if Force = Mass * Acceleration , so A=F/M, and the mass of your car is constant. So the way to increase A is to increase F. F at the contact patch of where the tire meets the road is given by (torque on the rear wheel axle) / (radius of wheel/tire). So if your engine is the same, the way to increase torque and hence F, is by mechanical leveraging, or gearing in this case. But unfortunately if you gear it lower, the engine will spin up faster....so if you can keep making the torque as the engine spins faster and faster, you can increase F by taking advantage of the lowered gearing (maybe a higher final drive ratio in the differential)......Or more likely, you leave the gearing alone and you increase torque output from your engine (hopefully at higher rpms) with modifications which will also increase F.

So S--K, it would be nice if the S52US engine would keep the same torque that it has at ~4000 all the up to 7000 but evidently the volumetric efficiency drops off most likely cause its tuned for a higher torque at a lower level. If you tuned it for max torque at 7000, there would be less torque available at lower rpms (maybe less fun to drive) ....and if looking at the dyno plot, the total area under the torque curve would probably be less if it peaked 7000 versus 4000. I think the Euro S52 engine's torque actually does peak at a higher rpm and I believe they have slightly lower gearing (6 speeds) and a higher (~8000) redline.

[Kevlar]

Bob... You are the man! Great explanation. I don't know how you do it... be I am definitely glad that you do.

As for OBD-II upgrades. I've seen a few. I've seen AA, vs. JC vs. Dinan. All upgrades offer little to no power on a stock car. The amount the offer a stock car depends on operating conditions of the engine along with the adaptation issue and how it's adapted previously.

The place where the upgraded software really starts to shine is when you add an intake and exhaust to the car. The ///M intake is restrictive. If you remove the baffles from the stock airbox, you see a net gain of 2-4 hp at the wheels

http://www.activeautowerke.com/dyno/
'96 M3 Stock vs '96 M3 with Aibox Baffles removed

I think the JC shart about the SI giving 35hp is a bunch of crap. I had his software in my car with an intake and exhaust and never got that much power. I have since switched out to the AA chip and I still don't get that much power, but I get 7ft-lbs of torque more over the JC chip at WOT.

Now the things that is hard to measure is the partial throttle. Since there is no real way to dyno a car under partial throttle. We can't get any real accuracy measurements. Only from what people 'claim' to feel. Under partial throttle and city driving, the JC chip feels stronger than stock (maybe that's where they get there 35hp number from) no doubt. Since I changed to the AA chip, the car feels just as strong... if not stronger. On occasion I have to make a Uturn to go home (you know). Normally, when I'd accelerate through the Uturn, the car would push (understeer). Last time (the other day) when I made the same uturn and what I'd assume to be normal driving... the back of the car started to slide out. I'm guessing the AA chip has more partial throttle power than the JC chip.

Alright... enough of my rambling.

[RS]

Kevlar, I did take that damn baffle out of my airbox and the engine definitely seems to breathing better at high rpm. I can feel a little more punch....so thanks for the tip.

[S--K]

Bob, you are the definitely one of the most knowledgeable persons on this board (if not the most) and definitely the nicest!! Thanks for taking time to enlighten the masses.

Do you visit the DTM board? Ben Liaw is on there and the rest of the guys seem pretty cool too, especially JamesN.

Thanks.