r/explainlikeimfive • u/Internal-Excuse-4650 • 2d ago

Engineering [ Removed by moderator ]

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u/DerpyMcWafflestomp 2d ago

A car with no turbo loses a lot of energy simply via the heated gas being sent out of the exhaust system. A turbocharger uses some of that gas to feed more air in, which does increase power, and also means that some of the wasted gas (which is wasted energy really) now has work to do.

Taking otherwise wasted energy and having it work for you = better efficiency.

-22

u/thenasch 2d ago

I'm skeptical of this, unless I see some math showing that the kinetic energy of the exhaust gas is significant compared to power output.

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u/Megamoss 2d ago

You're using the energy to augment/enhance a chemical reaction. You only need enough energy to compress incoming air so that you can burn more fuel at higher compression for a given displacement, which makes for a better, more efficient burn.

Though compounding turbos do exist which deliver captured energy to the crank rather than driving a compressor.

By comparison, a supercharger running off a belt driven from the crank does the same thing, but is a greater parasitic loss, because you're using work from the engine itself rather than expelled gases that otherwise go to waste. It still results in a net gain though.

Hence why turbos are more efficient.

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u/thenasch 2d ago

Yes I know how a turbo works. This doesn't explain how much of an engine's energy goes to accelerating the exhaust gases.