Quote:
Originally Posted by Christ
Piston speed isn't necessarily determined by engine speed, and the piston can fall away from the expansion of gasses at MUCH lower speeds than 6500 RPM. It's also dependent on stroke length.
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I guess I should have been more specific.
In my post I was referring to two engines of the same design and a average piston speed.
An engine with a 85mm stroke @ 2400rpm will have a mean piston speed of 22.31 ft/second.
This same engine at 6500rpm will have a mean piston speed of
60.42 ft/second.
Now according to Willard W. Pulkrabek book "Engineering Fundamentals of the Internal Combustion Engine" the average combustion flame speed of typical modern SI engine will have a flame speed mean of 82 ft/second @ 1000rpm.
At only 3000rpm the flame speed will increase to 246 ft/second.
As engines rpm increases the intensity of turbulence, swirl, squish, and tumble all increase, resulting in a faster flame speed.
Also with a modern fast-burn combustion chamber engine you will see a 95% burn at 45 degrees crank angle @ 3000rpm.