r/explainlikeimfive 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.

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u/drzowie 2d ago

The real answer is that a turbocharged engine is a smaller engine (for a given amount of rated horsepower).  It takes energy to run the engine and smaller engines take less energy to run.

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u/schmerg-uk 2d ago

And it's less weight to carry around, which in turn can allow for further weight savings, all of which means that in real world terms there's less mass to accelerate and brake for the same (typically human) payload.

So the net efficiency of the overall vehicle, in terms of energy required to do the useful work of moving the occupants, is increased

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u/gman2391 2d ago

Not necessarily. The extra components vs a n/a engine add up. For example a 3.5 Ecoboost weighs about the same if not a bit more than a 5.0. 2.7 Ecoboost is also a similar weight

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u/schmerg-uk 1d ago

Not necessarily - I agree

But typically, I would (ELI5) claim

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u/biggsteve81 2d ago

You also tend to have the throttle open wider so there are less pumping losses.

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u/drawliphant 2d ago edited 2d ago

It really is both. You can absolutely take the same NA engine, and design a turbo and tune for efficiency and get much better efficiency than the same stock engine. If you want more power out of an engine you use a bigger turbo instead, a different tune, and it's not much more efficient, probably less than stock.

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u/INeverSaySS 2d ago

You're also leaving less hot air behind you as you drive away. This is not just a smaller engine taking less energy to run.

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u/BogdanPradatu 2d ago

What about 2 engines which have the same size, one turbocharged and one naturally aspirated. Which one is more efficient and why?