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Old 05-15-2008, 12:07 PM   #4 (permalink)
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1999 Saturn SW2 - '99 Saturn SW2 Wagon
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steensn -

Daox is on the money. I don't think the IAT resistor mod will work because the ECU/PCM will normally be in "closed loop" mode. In that mode, the IAT sensor value is *ignored* in favor of the oxygen sensor. The oxygen sensor is used to try to keep the engine at the stoichiometric ratio of 14.7/1 (14.7 parts air to 1 part fuel).

Instead of doing the resistor mod, you can build an HAI/WAI (Hot/Warm-Air-Intake), where you route the input air in from the exhaust manifold. In that way, the engine will be getting "real" hot air that has a real effect on the oxygen sensor.

There is an experiment I need to finish where I hope to prove this behavior, but I have been too lazy to do it.

PS - The corollary to this is the "performance" resistor mod, where you put a bias on the IAT signal to make the ECU/PCM think it is getting cold air. I think this works because under *performance* driving conditions, you are typically driving at WOT (wide open throttle). Under WOT, the ECU/PCM will switch to open loop mode and use the IAT sensor to determine how much fuel to put in.


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