well, using that argumenat so does diff ratio, gearbox ratio, etc etc so come on - answer the Qs - why don't dyno operators need to know these things in order to calculate their results??? <{POST_SNAPBACK}> Hey Turbo6man I am not a dyno expert, just a hack, so back off man. But everything behind your flywheel MUST affect the RWKW. auto versus manual, - diff ratio - what grease and sh*t is in there - if your handbrake is on or not... I don't believe that dyno dudes will ever give you an actual figure for fly wheel KW. If they do give you a figure for FWKW, it is an estimate based on experience and factory claims for FWKW. The only accurate way to measure FWKW is at the flywheel not at the wheels. <{POST_SNAPBACK}> You've obviously missed the point - when was the discussion about FWKW? We've only been talking RWKW so don't make it any more complicated than that eh? So far no one can show even how the RWKW figures are determined or why they vary with different wheel sizes so don't get into FWKW at this point. If you go back over what I've said - it is that the figures presented mean J@CKSH!T. If anyone truely believes that running 17" wheels instead of 19s is going to suddenly give their car and extra 7 or 8% increase in power then how about we all go out and get 12" mini wheels? <{POST_SNAPBACK}> Turbo6man I haven't missed the point at all. It is all to do with Year 9 mathematics - moments to be precise. If the wheel you are using has a smaller circumference (,with everything else being equal) it will read more power on the dyno. QED