anyone....?

 

Don't get excited as the answer is no.

However, just looked at my plot, 204bhp at the wheels. 324bhp corrected power.

Anyone?

Mike

 

The wheel figures vs fly figures confuse me. Last RR day I went to I got 294 bhp at wheels, but as they just add an arbitrary 22% on for transmission losses ( don't seem to measure it ?? ) I got 356 bhp ( iirc ? ). At well lane last 2 visits 6 months apart, got 363 and 358 bhp - assume at flywheel, ( torque was 320 - 325 lbft ) so all seemed consistant.

The above figures e.g. 204 wheel bhp => 324 bhp seem odd???

Are there any standardised settings / corrections that all RR's should use?
I know there should be RPM measurement, ambient temp and atmospheric pressure measurements, humidity etfc. which lead to corrections ...

 

The flywheel HP figure is the sum of the HP "@ the wheels" and the drag measured during coastdown. The Coastdown drag curve is exponential. The wheels figure is meaningless without some form of drag measurement. All these factors affect the power @ the wheels. Tyre type/size/pressure/temperature, gear/diff ratio, gear oil viscosity and gear selected. The gear ratios and gear selected have the most dramatic affect because, simply put, the greater the speed the more the drag hence the lower the wheels HP figure.



The greater the speed the higher the drag figure and the lower the "@ the wheels" figure.



It should be noted that the drag figure measured on a rolling road is far greater than you would experience on the road as on the dyno the car sits on 8 small circumference rollers which deform the tyre. The drag measured is true though, you would have a lower drag and a higher "at the wheels" figure on the public highway.

I hope the explains some of the variations seen between different cars.



Rich

 

Thanks for the detailed explanation.