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Originally Posted by broadwayline
At part throttle boost is throttle and RPM dependent on superchargers due to the bypass valve.
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Fixed that for ya.
I came across this in the wikipedia article on superchargers, under the aircraft section:
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A supercharger has to take its drive power from the engine. Taking a single-stage single-speed supercharged engine, such as the Rolls Royce Merlin, for instance, the supercharger uses up about 150 horsepower (110 kW). Without a supercharger the engine would produce 750 hp (560 kW); with a supercharger the engine now produces 1,000 hp (750 kW), a total increase of 400 hp (750hp - 150 + 400), or a net gain of 250 hp (186 kW). This is where the principal disadvantage of a supercharger becomes apparent: The engine has to burn extra fuel to provide power to turn the supercharger. The increased charge density increases the engine's specific power and power to weight ratio, but also increases the engine's specific fuel consumption.
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So in that case, the engine has a 1000 hp output with the fuel consumption of a 1150 hp engine. Yes, a clutch and bypass valve will help with that, but if you're not using the supercharger, why bother installing it?
A functioning supercharger will reduce the engine's efficiency (in terms of BSFC), and a fully bypassed supercharger isn't going to improve the efficiency of the engine as the engine will be operating just like a normally aspirated variant... The supercharger will only be dead weight.
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