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Originally Posted by vswingfield
Sorry, but exactly wrong. When the vacuum goes down, you are opening up the throttle. You are implying that you get your greatest economy with your vehicle floorboarded!
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Sorry, but exactly right.
Quote:
Originally Posted by vswingfield
I gotta admit, "pumping loss" is a new one to me. I can see that there is some inherent loss of energy when pulling a vacuum, but still, the higher the vacuum the less fuel you burn, period.
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"Pumping loss" is the technical term for the energy your engine exerts to pump the exhaust out, and draw air in. Air you saying that freeing up exhaust flow does nothing for fuel economy?
You've heard of "displacement on demand" and "mutli displacement system" right? They improve fuel economy because a four cylinder with the throttle wide open and no intake vacuum is more efficient than an eight cylinder with the throttle half closed and loads of vacuum.
The pumping loss is why putting taller gears in the rear end kills the fuel economy. Does the wind resistance magically increase when you put taller gears in? Ofcourse not. But the engine RPM does increase, so you need to close the throttle a little more to keep the mass air flow the same.
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Originally Posted by vswingfield
Also, not all diesels are "turbo" diesels. Old Detroit Diesels had a mechanical supercharger (the 6-71 supercharger became famous on 426 hemi drag racers in the 50s and 60s) and were two-stroke diesels. Some other diesels have no supercharging at all.
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I'm well aware of the history of engine aspiration methods and application.