I'm going to send this new understanding of volumetric efficiency to my buddies over at Caterpillar. They will love it.
P.S. A turbo doesn't have a 1:1 Ratio between exhaust pressure and boost. One impeller is compressing the air flow so it has a different geometry than the one that gases push against! These differences make a big difference in how much boost you get for specific volume of gas accelerating the unit. Also you will notice that the Intake housing is smaller than the exhaust housing[sometimes you need to measure it to see the difference]-- this is because the intake is trying maximize pressure by having a higher rotational speed than the turbine. Where as the exhaust is trying maximize the volume of gas pushing the against the turbine thus increasing the speed of the compressor. It is like having an overdrive where you get more rotations out of the smaller compressor wheel to keep up with the bigger slower rotating turbine.... So really you have more a 4-5 or even 10 to 1 ratio in favor of boost pressure over that of exhaust pressure. This is why the turbo becomes more efficient as the exhaust pressure increases and compress wheel's rpm goes up! You know it is the damn centripetal force formula.
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