transmission loss

a mate of mine had his mk1 gti cabby on the rolling road at stealth this afternoon, its making 136.4 bhp at the flywheel…..but losing nearly 33% of this through the transmission, i think it works out to be 103 bhp at the wheels,  does that sound normal or does he have some clutch issues to worry about? (he can't tell if the clutch is slipping so i would assume not)

The obvious thing would have been to plot clutch slip (rpm/MPH) vs MAP, to see if it was slipping during the run. I guess they didn't hook up MAP though?

i'm not sure what they did as i wasn't there with him, he isn't to clued up about this sort of thing, its revs off the clock and sounds nice….thats about all he's bothered about lol.i just thought that a 30 odd horsepower loss was quite excessive,because my gti tintop was making 100 bhp at the wheels when it was standard and running, many moons ago! thanks for the reply

figure around 15% transmission loss as normal.

If a car is on the rollers, BHP can only be measured at the wheels.
The flywheel measurement is an estimate.

To measure the true flywheel power, the engine would have to be out of the car on a test bench.

103 at the wheels sounds OK, though the 136 might have been a bit exagerated to make your mate feel better!

i've had a look at the printouts he got from the rolling road session and it basically shows a smooth power curve with peak power of 136.4 bhp at 5700 rpm, then there is a constant decline in power after this, this is all plotted on a proper graph rather than just a table. the engine also makes it peak torque lower in the rev range than i expected, it peaks around the 4000 rpm mark.

went for a drive in the car today and its very eager to rev but just doesn't feel very quick….no faster than normal infact, it is quick as it pulls away from another mates mk4 1.8t golf with ease….just doesn't feel it if that makes sense  :dontknow: