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Old 03-10-2011, 12:27 AM   #13
Scooby Specialist
Member#: 30733
Join Date: Dec 2002
Chapter/Region: TXIC
Location: Houston texas
2007 tiny car


Even if you throttle with valve timeing you still have "pumping losses" I think for a fixed discplacment engine. I have to think about it more though. The problem is gasoline engines only work in a narrow air fuel range, so at some point if not at max power, you will need to be working against a vacume.

The way to get around this inherent compromise for spark ignition engine is to have one that can operate in lean burn (throttle with amount of fuel injected) or variable discplacement where the intake volume is always atmospheric but you vary the intake stroke or whatever to adjust the power level.

Either way, for a typical air throttled engine any restriction upstream of the throttle plate isnt doing any harm until the car is floored. In any part throttle condition it is simply changing the position the user needs to put the pedal to.
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