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IAT Resistor Mod

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  • IAT Resistor Mod

    IAT stands for Intake Air Temperature. It is a simple thermistor that changes its resistance according to the temperature it is at. The idea beind this modification, is that by changing the resistance to that of a cooler interpreted reading, you will get more fuel. While it is true that you will dump more fuel...its false that this is a good idea. Running rich is bad for performance, so you are just wasting your time with adding more fuel in this fashion.


    The stock computer already compensates fuel as it is, so trying to trick it into giving you more fuel is completely worthless. If you dump too much fuel, via switching to a colder resistance on the IAT while driving, you may even notice a puff of black smoke out the exhaust. Then, the O2 sensor will detect the overly rich mixture, and reduce the injector pulse width. This totally defeats the purpose or the IAT mod.

    • robertisaar
      #1
      robertisaar commented
      Editing a comment
      i got bored:

      here is how the IAT mod "works"

      it adds both advance and fuel via a few tables in the ECMs. i'm going to explain it and show with a 90 grand prix 3.1(running on the A1 mask), since i play with the most.

      you'll feel better throttle response due to more AE(accell enrich) fuel being commanded, and pretty much more fuel will feel better, up until you get past the point of roughly an instantaneous ~12.9:1 AFR, then you'll start getting into a rich bog. now, you'll notice that the AE added also goes up at higher temps; this is to help cool the motor, since if you're sucking in ~300*F air, you're likely damaging something and fuel will evaporate, giving a small handicap. also notice the basically 0 number at -40*F; that is what you'll get if you disconnect the IAT altogether.



      next, we have another fuel modifier, but this one doesn't deal with throttle response, it has to do with adding more fuel at all times(until the O2 sensor corrects for it); airflow multiplier vs IAT(technically, airflow doesn't multiply based on temps, but it does get denser at colder temps, meaning more oxygen molecules for the fuel to bond with during combustion), and as we see, almost a linear change in the air temp vs the amount of air that is "multiplied".



      now, for spark i have to switch to a different mask since A1 doesn't modify advance based on IAT, so i'll move to 1FA(94-95 3100 A-body), and as you can see, only when you move beyond 46*C(since the PCM interpolates the table) will you get any change to the advance and it looks like it will pull a maximum of 4.25* of advance depending on load.



      so, there ya go, that's what the IAT mod will net you: lying to the ECM/PCM to trick it into more fuel and advance, something that would be better done through actual tuning.
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