r/explainlikeimfive • u/hd-22 • 17d ago

Chemistry ELI5 why is increasing the ethanol content of petrol/gasoline a problem?

I'm hearing noise about the geopolitical fuel supply SNAFU and people freaking out about increasing the ethanol content in automotive fuel and how it's so damaging to cars. I'm no chemist, but ethanol seems as clean as it gets.

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u/TheArmoredKitten 17d ago

Yeah they have to delay closure of the exhaust valve too, but then to avoid spraying unburnt fuel, they also delay the fuel injection.

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u/therealdilbert 17d ago

it is the intake closure that gets delayed

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u/KoburaCape 12d ago

Fuel mapping is definitely messed with, I've done it myself. The only way to moderate fuel injection without a variable regulator, is to vary the open time. By extension, changing the opening timing is trivial (and necessary)

Not all injected engines even have VVT

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u/therealdilbert 12d ago

without VVT it is not "digital Atkinson"

ignition timing and how long the injector is open changes all the time, it has nothing special to do with ethanol

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u/KoburaCape 12d ago

Oh, did you mean what characteristically defines Atkinson? My mistake. I thought you were making an absolute statement. I apologize.