In Reply to: Wrong... posted by Omar on September 14, 2001 at 12:27:23:
2000 M5 304hp X 1.21 = 368hp
2001 M3 248hp X 1.21 = 300hp
The above stated cars have different drivetrains than the E36 M3. Thus, their drivetrain loss will be different. It's an apples to oranges comparison that you're doing.
The 1.21 correction factor ONLY applies to a 5-speed 6-cylinder. An automatic 1995 M3 will have a different drivetrain loss, as automatic trannys typically take up more power. Likewise, a 6-speed manual tranny will have a different loss than a 5-speed manual tranny.
I have used both dynojet and mustang dynos and there is a significant difference in the numbers they generate. From my experience dynojet numbers are about 15%-17% more than the mustang's.
So have I....I put my '95 M3 turbo w/6psi on a Mustang Dyno and got 280rwhp. Using a 1.31 correction factor gives 367hp....Yeah, right! with 6psi boost? I don't think so. Using 1.21 gives 339hp, which is more inline with 6psi.
Also, I've seen Corvette's at some shows be run on both Mustang Dynos and DynoJets back to back, and the rear wheel numbers have been within 1% of each other.
One method to figure out what the correct/estimate horsepower for a car (in any type of dyno) is to compare the numbers to numbers from a stock car (from the same dyno, same conditions).
Even doing this is not going to give you the correct drivetrain loss. At the end of the day the rear wheel horsepower is what counts...
I agree with "rear wheel horsepower is what counts". It doesn't matter how you measure it, rear wheel hp is rear wheel hp. It's the same value no matter what kind of dyno is used.
'95 M3 turbo