The $20 an hour Cessna 172 experiment

Re:The $20 an hour Cessna 172 experiment by jabl on Friday February 10, 2023 @02:18AM (#34736683)

> I would guess that whatever makes it cost so much would equally apply to this solution once it is certified and not experimental.

Bingo! Yeah, I was wondering the same while reading the article.

> a pretty ancient design (e.g. pushrods)

Does it matter? The engine is significantly derated vs. the original car engine, so max rpm is going to be much lower, thus no problem with valve float.

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Re:The $20 an hour Cessna 172 experiment by UniverseHacker on Friday February 10, 2023 @12:27PM (#34742742)

Modern direct injection diesels still use OHC, even though they run at really low RPM, so valve float can't be the only reason virtually all modern engines use it. I think this is because it allows for larger and better positioned valves, or even more valves (e.g. DOHC/4 valves per cylinder), making the engine breath better. I imagine the advantages of that would be even greater at altitude.

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Re:The $20 an hour Cessna 172 experiment by jabl on Friday February 10, 2023 @02:03PM (#34744123)

I'm not saying OHC aren't better, they certainly are (in most respects). Just saying that I wouldn't consider pushrods a showstopper either.

(As an aside, when aviation engines started going with 4V designs in the 30'ies, it wasn't only about breathing, but better cooling of the valves was an equally big motivation.)

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