Originally Posted by Karl

As said above:

One answer in selecting C.R for a given engine - cylinder pressures and fuel octane rating


The cylinder pressures are calculated via bhp required, engine capacity, rpm and C.R.

All this talk of how mapping has moved on is nonsense! all thats changed is engine mgmt is now more sophisticated in the control mechanisms it offers. The actual ignition and fuel mapping of a high comp engine is the same now as it always has been.

In laymans terms if you want a road car of over 400bhp go 7.*:1 for the C.R. otherwise 8.0/7.8:1 is fine for sub 400bhp YB engines.