Wheel torque / bhp vs clutch torque / bhp on r/r

[P_G]

I'm thinking of taking a little trip to Awesome GTi to have new springs fitted and thought about using their rolling road at the same time. However I'm told their rolling road only measures from the wheels and not from the fly wheel / clutch.

Therefore I'm curious to know if there's a calculation to convert torque / bhp at the wheels to that of the clutch to work out what figures the engine is producing?

If no direct correlation I'll probably leave the rolling road session for somewhere else at a later date as I would like both sets.

[wmrme01]

wouldn't you get a higher value of the clutch?

When tuners give you your torque/bph which should they use.

probably that why its best to tune with a rolling road giving actual before and after figures, so whether it measured from the wheel or engine you can actually see the increase.

[gambba]

As neila says the real interest is the BHP not the raw HP.

BHP is the resulting figure after taking into account the the drag of the driveline i.e. transmission, differential, wheel bearings twist in the drive shafts etc.

The above is especially relevent in your case where you have 4WD and the powerloss is significantly higher than 2WD.

Torque is the one to really care about

[Tobes49]

Every rolling road only reads the wheel HP and a calculation works out the flywheel HP, The only way to read the engine(flywheel) HP is to take the engine out run that on a engine dyno.

[P_G]

Thought might be the case Tobes, I'm going to wait until I find a road that can do wheel and clutch figures.

I agree cars should be done of on wheel BHP, however most quoted figures are on engine / clutch bhp and torque. Having seen wheel plots on B7 S4's they don't even get above 280 BHP at the wheels with remaps and Milltek's added.