Quote:
Originally Posted by shdw  What are they concerned with keeping safe as MP/RPM spread increases and how does this link with different engine powers having different MP/RPM spread limits? |
Detonation limits, I believe. Reducing RPM increases BMEP (brake mean effective pressure) in the cylinders. As for why it varies from engine to engine, displacement does appear in the formulas, with larger engines tending to reduce the increase in BMEP produced by RPM decreases. Also, compression ratios probably have a role, with higher compression engines having a greater propensity to detonate.