Thread: Engine Braking
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Old 10-02-2012, 08:45 PM   #12 (permalink)
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Manifold restrictions in gasoline engines restrict the flow of air into the cylinders. The lower mass of air means lower compression in the cylinder which means much less power produced for the same amount of fuel consumed. This is because higher compression is a better "lever" to produce power. An engine produces power by compressing air and fuel then igniting the fuel, which expands the combustive mixture which produces pressure to push the piston and make power. If you reduce the in cylinder compression then you have much less power produced.
Why is it not then the case that the point of highest torque is the point of highest efficiency? I was discussing this with someone who thought this to be the case, and I found myself unable to effectively refute that except by saying that high rpm's are unefficient. I know that torque is technically ft.-lbs. but I have always thought of it as ft.-lbs per stroke of the engine. If torque is indeed the amount of work done per stroke of the engine, then the point of highest torque would be the point of highest compression ratio, and probably then the point of highest efficiency.
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