Quote:
Originally Posted by CanAutM3
I am not sure I am reading you right. My understanding is that for a given RPM and displacement, the quantity of air to fill a cylinder and the time it takes to do so are exactly the same regardless of bore and stroke. So the charge velocity in the intake tract would be exactly the same (if we assume same valve size as you stated).
However, the engine with the larger bore can have an advantage at higher RPM because bigger valves can be fitted, thus increasing volumetric efficiency.
I also highly doubt that the S65 has a volumetric efficiency higher than 100%. There was a good discussion in another thread on this topic. My guess is that a volumetric efficiency between 80% and 85% at power peak is more realistic.
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You have to excuse my language skills, Volumetric efficiency was what I ment when I said "filling grade". Best VE are measured at torque peak, not power peak. S54B32 has a best VE of 106% in the standard E46 M3, and even higher in the CSL,(dont know the excact number here). Normaly VE will be a bit lower in V8s but as low as 80-85%?