Originally Posted by The Usual Suspect
whats the diffs between high comp and low chipper? i thinks its lower the more boost you can safely run?
Essentially mate yes.
Basically its all about managing peak cylinder pressures.
If you run lots of boost and lots of CR, then cylinder pressure sky rocket and you risk detonation, to combat this you have to retard the timing and that then loses you power.
Its very application specific though, if you are using 108ron fuel you can run high boost and high CR at the same time easily.
Also at higher RPM, because the cylinders fill less effeciently, you can run more boost without needing to lower the CR.
My own LET engine im building is very much like that, 8.2:1 compression and 8500rpm
Where as a cossie tuner going for 500bhp would normally use 7.2:1 and a lower rpm range.