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Old 03-02-2007, 12:48 PM   #1
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Default air fuel controlers

what do you know about ait fuel controlers? Ive seen sme apexi a/fcs that look real sexy. are they worth the money?

also, i would like to get a single electronic display that will tell me everything i want to know (ie. a/f, oil temp. oil psi, fuel psi, my horoscope, ect.) seen anything like this?
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Old 03-02-2007, 12:58 PM   #2
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Yes, they are sexy.

But worthless.

These devices work by intercepting the airflow signal into the ECU and modifying it. Basically, they lie to the ECU about how much air is going into the engine.

The problem inherent is that a naturally aspirated Miata engine, running at full tilt boogie, is already just about maxed on the AFM signal. There's not much higher it could go, so the apexi box doesn't have much range to work in. If you double the actual airflow there's just not enough range left to double the AFM signal.

You can sort of get around this by installing larger injectors and using the AFC to lie in the opposite direction- tell the ECU that *less* air is going in. But now you get into problems with idle and driveability at very low load conditions.

And of course, you don't get any ignition timing control with these.

Not to say that some folks around here haven't used them, but probably not as a "complete" solution managing a boosted engine, without at least an AFPR or a different AFM.

Managing a boosted engine electronically (without an aux fuel pressure regulator) is best done with a piggyback ECU, or a full standalone. These devices adjust fuel the right way- by directly modifying the fuel injector signal lines, rather than by trying to trick the ECU.
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Old 03-02-2007, 01:52 PM   #3
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Safc works but it is clunky with no TPS or map
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