Stock Maf Limits

Mitco39

Well it stops being able to measure the air over a set value. Lets say this maf maxes out at 80 lbs/min of air. The engine is using this "metered" air to determine how much fuel to inject during open loop operation (under load). All is fine as long as the tune is such that the amount of air going in is correctly matched up with an amount of fuel going in.

But now what happens if you run 90 lbs/min of air. Well as far as the computer knows your still only running 80 lbs/min. So it injects enough fuel to satisfy 80 pounds not the 90 your are running. So you start to lean out. And leaning out will only last a short time before you detonate and pop the engine.

If your tuner wasnt watching it you would see it on the dyno during a WOT run, look at your AFRs, if they appear to lean out as your rpms increase then you could very well be seeing the limits of the MAF (of course this is invalid if the tuner for whatever reason leans out the mixture via the target tables or if your actually draining your fuel rail).

That would be the easiest way to catch it without having access or seeing a log of the car.


For me right now I am running very rich so that when I hit the limit of the MAF I still have more than enough fuel to satisfy the burn. Its unsafe but as long as boost stays consistent I can have some safety in it like this. Still very undesirable and that is why I am looking to fix this issue.

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