how come bikes run with much higer CRs i.e. around 11/12+ whereas car engines are around the 9/10 mark?

they rev much higher

in iwch kinds?

i think bike engines are more designed to the limits..

and production cars needs to be cheaper..

also more CR ratio means more power..
(as long as there is no uncontrolled fireing - detonation- )

maybe piston area is a point..dunno..

in the end is the same ideal mixture on a higher pressure dunno..

Tks

It is dynamic rather than static compression ratio that is important when talking about maximum allowable compresion ratio. Static compression ratio is normally quoted since it is straightforward both to calculate and understand. Dynamic compression ratio is a little more complex and is a function of static compression ratio, valve profile, engine speed etc. As a rule of thumb, to maintain the optimum dynamic CR, as engine speed (and valve duration) increase static compression must also be increased. Hope this makes sense

dynamic compression ratio is due to variable volumetric efficiency.

also bike engines are better designed to deal with high compression, better cooling, more combustion area to volume, also they tend to have forged pistons so dont suffer as badly when detonation does occur.


in the end more compression means more efficiency if done right so more power. im planning to go to around the 13.5-14 mark on my r1 so it should still just be able to run on super once the internals have been ceramic coated.