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      11-01-2012, 11:18 PM   #32

Drives: E92 M3 x2
Join Date: Feb 2012
Location: the wood

iTrader: (0)

Originally Posted by highrevs
Originally Posted by THE-FN-MAN View Post
Impressive man! For shits and giggles where dues the M3 fit in with regards to aero compared to these two. My car is pretty much as modded as it can get short of a built motor and I hang with my buddies Z06 until about 4 when he starts to pull.
I had to take some liberties with the relevant specs for the M3 since we have coupes, sedans, and convertibles. Looks like 0.32 is the worst case drag coefficient from a post claiming numbers directly from BMW; usually take the worst case in these scenarios because you can say that in reality the results are probably better. For width and height I used the coupe values [1] (reason below).

Not surprisingly, it did pretty damn well. With respect to drag force it's literally right on top of the Z06; had to use some formatting trickery to distinguish the two. That's pretty impressive given that the Z06 is four feet tall.

The one big thing I would infer from this is that drag can probably be tossed out when comparing the M3 and Z06. So in theory if the two cars have the same power to weight ratios and other effects (like gearing and traction) are negligible the two should be very close. What kind of power are you putting down?

Take a look at the attached wind tunnel test of the M3 (why I went with coupe dimensions). It shows that any one method of testing or modeling isn't 100% accurate. What I'm guessing is the derived drag coefficient (0.33) isn't what BMW listed for the M3 coupe (0.30). Another thing it shows is that my model isn't 100% accurate because using width and height to estimate frontal area ignores the fact that the bottom of the car is several inches above the ground. They listed frontal area as 2.17 meters and based on width and height I calculated 2.57 meters. Of course when we're comparing different cars and each one has a different height above ground, even more accuracy is lost.

This is a perfect example of why bench racing is never accurate. Results of any one run are based on so many variables it's insane. Drag force varying between cars and getting even more complicated when winds are included. Driver skill, transmission type (shift speeds), gearing (number of shifts), power to weight, torque to weight, traction (in every gear), tires, it goes on and on.
Loving the info brotha! My car dynoed at 591 and his Z06 at 587. So I figured on any given day those numbers could flip flop and he could have a few more and me a few less. I figured on a cold night though both of us are probably right around 600 to the tires. Although recently I've been told that running meth in cold weather can actually cause me to lose power which is news to me. Our last run was on a return trip home from a full track day and my car was saying the temp outside was 101 degrees. My car still felt quick but I definitely felt I had some heat soak going on as well I didn't have meth on. We were even pretty much all through 3rd which I was happy with considering I darted at such a low rpm in 3rd as I knew his car had a ton more torque than I did and as soon as I shifted into 4th he pulled on my pretty hard.