How a Car Engine Works

Re:How a Car Engine Works by userbinator on Sunday April 10, 2016 @12:38AM (#11464919)

This is a problem if you try to make a high-revving engine, for instance, in order to get better fuel efficiency at low speeds and good power at high rpms: to allow high-rpm operation, you need stiffer valve springs, but this significantly affects your fuel economy.

The alternative is to just not design for high RPM; the most efficient internal combustion engines are huge low-speed two-stroke diesels used for ships and stationary generators.

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Re:How a Car Engine Works by extrapickles on Sunday April 10, 2016 @02:57AM (#11465229)

Large marine diesels have very low RPM. Some of them red-line at 102 RPM, and normally operate much less than that. A typical passenger cars idles at 1200RPM and redlines around 6-7K RPM.

Then again a single piston in the marine engine weighs 2x of an entire car so they can easily do things that one wouldn't bother to do on a smaller engine.

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Re:How a Car Engine Works by Grishnakh on Sunday April 10, 2016 @11:23AM (#11466517)

>A typical passenger cars idles at 1200RPM

No, they don't. 750rpm is pretty typical these days. They'll idle at higher speeds when cold, though, to warm up faster.

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Re:How a Car Engine Works by Grishnakh on Sunday April 10, 2016 @11:24AM (#11466525)

Huge engines aren't feasible in cars. More mass to carry around means lower fuel efficiency. Stationary plants don't care much about mass, and with ships it doesn't have that much of an effect.

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