General ECU question

[mechdaddy]

hey guys, general question about the ECU. In terms of controlling the air/fuel ratio, how does the ECU work? More specifically, what would happen when a CAI or a supercharger is put in use, would the ECU make adjustments to the ratio accordingly? thanks

[GregFarz78]

I'm no expert but there are factory preset fuel maps, no big deal when you add a CAI but a supercharger you need to get the ECU reprogrammed to make the necessary adjustments.

[Matt95GT]

It is a combination of fuel maps/tables, and when in closed loop, A/F feedback from the O2 sensor. In closed loop, the PCM is pretty robust in maintaining stoich A/F... but that does not apply to WOT acceleration.

Does it "make adjustments" when it really counts (full throttle)? No.

Will it matter for most mild bolt-on "flow" type mods (E.g., CAI)? No - as these mods do not significantly impact A/F ratio. A CAI or exhaust simply take less work for the engine to "breath."

Will it matter for boost? Yes - blowers/turbos can physically stuff more air into each cylinder. The PCM isn't aware of boost, it keeps injecting the same amount of fuel, so you get a very lean mix resulting in engine-breaking knock and/or high cylinder temps that can melt holes through pistons.

[mechdaddy]

great, thanks a lot