2.7 RS Spec hp. at the wheel??

[rrcrawford70s]

I am considering putting my car on a dyno. I want to know how much hp and torque my car REALLY puts out. The motor is 2.7 RS Spec., with the 2.7 MFI.
I know the books state it is a 210 hp motor. What "should" mine be at the wheels?

[Tim Walsh]

at 15% drivetrain losses you get 178 RWHP
at 10% drivetrain losses you get 189 RWHP

[rrcrawford70s]

Thanks for the quick reply. How do determine the 10 or 15% loss for my car?

[Tim Walsh]

I think it all depends on what kind of condition the rest of the driveline is in. I'm not an expert by any means but from what I've read most drivetrain losses are somewhere in that ballpark. Someone who's actaully done real dynoing would know more. I've just done the online dyno

[Bruce M.]

I think you'll find that most drivetrain losses on 911's are pretty damn close to 15%, maybe a shade under. Which is actually better than a lot of more traditional, front-engined cars. I've actually done a crank dyno/wheel dyno comparison, with other factors (gas, ambient temperature, etc.) reasonably constant. Loss was 14%.

I own a 930, but there's no reason I can think of that the presence of a turbo should affect loss....

[NYSCAR]

welp the question still remains on RWHP though, because we're all assuming 14-15% losses on porsches published figure of 210 hp. Real dyno numbers would be interesting....

Brad

[CamB]

My dyno guy used only 9% losses, but I think Bruce's 14% is the best figure (he did measure it!!).

210 * .86 = 181hp

Don't get too hung up on it within a few hp - there are heaps of factors which can affect the output. As important as anything is how smooth the curve is and how well it drives.

[Bill Verburg]

15% seems to be the most commonly used figure for drivtrain losses.