...Even a dyno is not perfect, ( eg air intake tract etc may not be the same as fitted in the car)
A properly calibrated RR ,used accuratly and correctly 'SHOULD' be accurate. Ulfortunatley more often than not its not. As a comparitor for checking changes in output (after mods) it fares slightly better but again too many variables to rely on it.
To summarize:-
-Flywheel BHP is what you need to measure (ie WHP +measured losses added on) . The WHP on its own is meaningless, as is a WHP figure with '20% just slapped on top ' used as your Flywheel HP.
-Very large differences in WHP & Flywheel HP could mean binding brakes etc.
-Most RR's are capable of recalculating & changing the power figures depending on the ambient pressure & air temp. (to a DIN standard or whatever) Therefore it shouldnt make any difference to the figures you get presented to you. In reality some places just bang in an air temp (say 18Deg C) and leave it there come snow or shine! So if its colder than that you get a higher reading and if its hotter you get a lower reading.
Best Regards Roland GTT
