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Old 12-06-2010, 04:32 AM   #144 (permalink)
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Originally Posted by NeilBlanchard View Post
Keeping in mind that piston engines were invented for steam power, and adapted for gasoline -- steam has a (more or less) constant back pressure, so the pressure in the cylinder is maintained all the way to the bottom of the stroke. Whereas, ignited fuel in a much shorter expansion time, and since it start very near TDC, much of the peak pressure is "wasted" in bending the crankshaft sideways, rather than developing torque...
I don't understand entirely, you say the peak pressure at tdc is the issue, but that pressure doesn't go anywhere till the piston starts moving anyway, so what's the problem?!? Where did you see references to %50 efficiency improvements on cam based engines (and was it clear that it was a tdc based gain)?
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