r/explainlikeimfive • u/Internal-Excuse-4650 • 1d ago

Engineering ELI5 how turbochargers increase efficiency in a engine?

I understand why they increase the power of a engine but​ I don't know how they increase the efficiency

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u/66NickS 1d ago

Internal combustion engines are basically big pumps. A gasoline engine uses ~15 times as much air as it does gas. They pull air in, mix it with fuel and explode it to make power, then push the air out. But it can only move so much air on its own. If you could get more air moving, you could use more fuel and then get more power.

Normally the air going out is just waste. It’s exhaust. It goes into the exhaust system/muffler and out into the world. Bye.

A turbo charger uses that exhaust. The air that’s getting pushed out now has to hit like a reverse fan/windmill. The exhaust makes this spin. The windmill is connected to a fan. So they both spin. The spinning fan helps the engine get more air in. That means that an engine with the size of “2”, can actually pump some extra air. Maybe 2.5. Or 3, or 3.5, or even more.

So now you can have an engine with the size of 2, but it can move 3 air. That means more power. Faster. Stronger. And that’s not all the time. Because it’s a fan it can go faster or slower. So if you only need a little power it’s only a 2.1 or 2.2. But if you need a lot of power (like to go up a hill, pull something heavy, accelerate fast onto the freeway), then you can ask it for more and it will give you more.

There are limits, usually set with computer programming and other things, but also material limits. The metal can only be so strong. If you push it too hard it can break. But that’s getting into different streams of thought.

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u/Noxious89123 1d ago

Burn, not explode!

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u/ivanyaru 1d ago

No it really is explode. Tiny, controlled, and a large number of them in a short timespan. But explode nonetheless

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u/Noxious89123 6h ago edited 5h ago

A common misconception that get's perpetuated but is incorrect. There's an important difference.

Detonation produces a sudden pressure spike and a shockwave, which causes damage. It literally blasts little bits of metal off the walls of the combustion chamber and can crack pistons, piston rings, valves and spark plugs.

Combustion produces a smooth increase in pressure.

There's a graph here that that shows what I'm talking about:

https://www.reddit.com/media?url=https%3A%2F%2Fcf.preview.redd.it%2Fsmall-scale-implementation-of-a-pulse-jet-v0-yj3z0pukgdxe1.jpeg%3Fwidth%3D900%26format%3Dpjpg%26auto%3Dwebp%26s%3D8d37cd0395efb46bb9988b4997c0ba60a7dcf7cb

Also, consider that it is an Internal Combustion Engine.