[richtazz]

Piston speed doesn't affect compression, but it has a huge affect on detonation. The faster piston speed will cause the air/fuel mixture to be more violently tumbled around in the cylinder as it is drawn in and compressed. This is what leads to more prevalent detonation in a long stroke engine at higher RPM. 2 engines with identical compression ratios and displacement (1 long stroke/smaller bore, one short stroke/larger bore) will perform much differently, and their torque/hp peaks will be at much different RPM. A long stroke engine will have a lower rpm torque peak vs a short stroke engine. However, since the reciprocating assembly is more compact, a short stroke engine is capable of higher RPM, all other factors being equal.