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BHP At Wheels vs Flywheel


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There is no calculation. The losses are entirely based upon variables which to measure would be far more complex than simply measuring run down lossses.


Factors such as tyre temperature, compound, pressure, tightness of straps securing car to rollers, spring rates, transmission and diff type/wear/ratios all have an influence on the power measured.


Measurement of run down losses, which is where the clutch is disengaged and the car allowed to coast to stationary after the power run will give the closest indication of true crank power, but unfortunately the calculations used to derive the wheel power + power losses are not simple and vary from software package and version.


If you have 147 at the wheels, it fair to say you could be looking at up to 200 at the crank but I doubt it would be over that figure.

Also is the 147 corrected for air temp and barometric pressure?


Post the plot here and we can guide you.


A std Busa puts out 170bhp, what have you done which could raise that?






Edited by - EFA on 26 Apr 2011 08:52:32

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Krismuss, EFA is spot on, there is no accurate calculation. Only way to do it accurately would be to bench dyno your engine.


Unfortunately different dynos give different readings and the different dyno technicians decide on assuming different losses. The more % losses they assume the better your engine looks to be performing.


However in the real world the power at the wheels is all we are really interested in. Suggest you see how it goes and then when you decide you want more power and you upgrade it, go back to the same dyno and in that way you can compare previous results.


If you get someone who knows what they are doing and you get the engine re-mapped on the dyno you will find you get a much smoother power delivery. If you are running a busa the powercommander is a good first option to allow the engine to be mapped. Following that you can upgrade to an MBE system.






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Just re-read your post, sorry for bleating on, didn't realise you needed it for your insurance policy.


I'd just go with your rolling road results. You don't know what losses you have and the smaller value the better I'm sure.



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