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quantizedself t1_j6d8yjb wrote

The maximum efficiency of an ideal combustion engine (Carnot cycle) is only 50%. This is a theoretical limit, no real engine can actually reach this efficiency. The fact that we have engines in the 30% range is already pretty impressive.

Why aren't the improvements bigger? Well, because the closer you get to that limit the harder it is to get closer to it. In other words, it takes increasingly bigger technological and engineering advances to make increasingly smaller improvements to efficiency as you approach that limit.

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NemyMongus t1_j6ddqf8 wrote

Mercedes AMG reached 50% thermal efficiency with their Formula 1 engine about 5 years ago but your point about no “real” engine is still very valid. The F1 engine is using hybrid tech to reach that and is more expensive that many homes, let alone cars. They also are not using standard fuels or oils either. The engine reaches that thermal efficiency not while idling or going at low speeds, it does it at full throttle producing over 1000hp so, while fuel efficient in relation to other F1 engines, I wouldn’t be surprised if the semi truck used to transport the cars from track to track get better MPG.

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quantizedself t1_j6dfuf7 wrote

That's interesting, I'll have to read up on that. This limit is for purely thermal engines that run on a hot and cold heat transfer cycle. So I can imagine something hybrid would do better, but I'd be willing to bet that if we took a close enough look at that engine we'd find the thermal only part of the engine being under 50% efficient, and the rest was boosted by a different system.

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