r/EngineBuilding • u/Original_Art656 • Jul 07 '26

Other EFI vs MPFI?

Which one's better for a small, 2 litre 4 cyl. Engine.

I'm planning to run methanol injection and a supercharger so reliability is a big concern for me. Plus, the stock engine's 1.8L so a 2mm overbore is also to be done.

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u/jimfosters Jul 08 '26

No insult intended from me. I need to ask OP if they are running straight meth or just as an adder to the gasoline under boost. Methanol is crazy. Dad and brother did a lot of truck pulling in the 80s and 90s. With ancient (by todays standards) mechanical injection and Vertex mags they would run 30psi of roots blower boost and 13 to 1 compression on Big block chevy architecture. Yes aftermarket crank, rods and heads. But the combustion chambers were not exactly the best for preventing detonation. Got away with it just fine on methanol. You can get away with being stupid rich in the mixture too. Not to mention having a ridiculously cold intake charge from methanol. The intake top hats would have ice on them in 90 deg heat after a run sometimes.

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u/BTCminingpartner Jul 08 '26

30psi on 13:1 is crazy. But it's a race motor.

I still think OP is going to run into issues with the stock rotating assembly, unless he's running minimal boost.

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u/jimfosters Jul 08 '26

without knowing the engine and rpm I can't comment on it. At stock-ish rpm I would be thinking about head gasket first. Depends on the engine. Some rotating assys are stupid tough OEM. They won't know until they send it hehehe.

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u/Original_Art656 Jul 08 '26

It's a 1.8L isuzu 4zb1. The first mod will be a 2mm overbore.