E30M3

>>When you say you do have to go at it in 1 gear just like a chassis dyno, can we use any gear, or do we have to use 4th-5th to gain the closest 1:1 ratios? If we do have to use 4th-5th, that could be a problem given the speeds we'll be at by the time we hit redline!<<

You can use any gear you want! I use 2nd a lot. It has higher drivetrain losses than the higher gears (1:1 is lowest usually) You can adjust for this easily by changing the loss factor and usng the correct gear ratio in the program. The guy is hard to reach at times - this is kind of a hobby thing ya know. If you use 2nd all the time you can compare mods easily as long as you keep things constant.

Stan

RicePimp

[QUOTE]Originally posted by Shamu
[B]When you say you do have to go at it in 1 gear just like a chassis dyno, can we use any gear, or do we have to use 4th-5th to gain the closest 1:1 ratios?

E30M3

>>Wind resistance in 4th and 5th would be really high. High enough that the simple wind resistance calculations based on Cd and frontal area wouldn't be enough to get good results. The drivetrain losses are higher in the low gears, but that is easier to correct for and the results would be more consistent<<

Not if you do your own coast down and other tests. To get your own rolling resistance and CdA. It's not that hard. And that is only if you want to get a run to directly compare to some other run on say a chassis dyno. The bigger problem is suitable road that is straight, flat, and safe. I do tuning of this sort all the time. The RELATIVE differences are what really matters. Speed to speed tests are super valuable. That is part of how I got my E30 M3 to run so well. Roughly a second faster in the 1/4 mile than stock, for example, and over a second faster 0-60.

Stan