Flywheel power from Hub

[JP825]

Can anyone show me the real calculation from a dyno hub powers to flywheels power.

Pip said is around 20% and I am not so sure about that.

:p

[petemillis]

There are loads of different theoretical calculations. The correct answer for "how much is my transmission loss?" is different for every car - and even the same car can have different losses depenind on the oil used, wear and so on. The only way to get the "true" value is to actually measure both the hub or wheel figures and the fly (engine) figure.  
The best that can be hoped for is an estimate of the fly figure calculated from an "estimated" transmission loss from the wheel or hub figure. And some estimates could be better than others. But all transmission loss figures generally fit in the 10 to 20% range.
My personal favourite calc is:

ATW hp + 10hp = ATH hp    assumes 10hp loss between hub and wheel
ATW hp/(1-12%) = ATF hp  assumes 12% loss between engine and hub

Seems to fit nicely in the 10 to 20% range.

[Glenn Butcher]

My theory is a nice quick/simple one - just add 100HP from the RWHP figure.

So if 300RWHP then 400FWHP.

There are too many variations, and then you have to take into consideration the different dyno\'s.  One dyno can read different from the next, silly things like depending on what mode it is in etc.

[Oedipus Rex]

personally I like to think I have really huge power so I add 400hp to my hub figure making my 7 a whopping 717.8 fwhp.

By my calculations my Rex is the most powerful in the UK.