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Intake Air Temp sensor

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  • Intake Air Temp sensor


    I have a 2001 NB8B (MK2.5) MX5 with coldside FFS kit, running the standard flexible hose intake piping to a pod filter.
    Currently my intake temp sensor is in the pod filter, which would be reading a much cooler temperature then the intake manifold temperature.

    I want to install an intake air temp sensor into the intake manifold below the blower, so that the temperature readings are more accurate which I assume will mean my car will run safer.
    I'd like to install the IAT sensor next to the manifold boost pressure sensor.
    This means I'd have to drill/tap a new hole in the manifold, but I don't want to remove the entire supercharger and manifold to do this.

    I was wondering if I could possibly install the IAT sensor in the manifold pressure sensor hole (see image here), and then get manifold pressure from somewhere else? Even though it looks like there isn't any other lines going to the manifold post blower.
    Otherwise it would be good if I could split the blower from the manifold, but I tried that previously when it was off the car and I could not get it to come apart.

    Or is there some way I can safely tap a new hole in the manifold without removing it from the car and without getting metal shavings in my engine?

    Any tips?

    Last edited by .andy; 02-23-2020, 04:32 PM.

  • #2
    The IAT in 94-05 Miatas is not based on intake manifold temperatures but intake air temperature coming into the air filter to the MAF. The reason is that for the MAF to calculate actual "MASS" of the air coming in so the ECU knows what mass of fuel to add, it uses a "hot wire" element in the MAF and needs to know how much the wire cools with the incoming air. To accurately calculate the cooling, it needs to know the temperature of the incoming (intake) air. For proper air to fuel at idle and cruise, the ECU wants to provide 1 pound of fuel for every 14.7 pounds of air. That is the stoichiometric AFR for complete combustion of the air. If you were to move the IAT sensor to the intake manifold where the air is warmer, the ECU would make the wrong calculations and, if I recall correctly, the AFR would be lean as it would under estimate the mass of incoming air. Once it knows the mass of the air coming in, it doesn't care about the temperature of the air in the intake manifold as the mass doesn't change. The density changes but the mass of air going through the engine is the same.

    1990 with FFS Coldside. At least 260 WHP NON-INTERCOOLED


    • #3
      Thanks Tom, very informative.

      So really I should look elsewhere for adding engine safety, such as coolant reroute and better radiator


      • #4
        I am not a fan of the coolant reroute. Here is my dissertation:

        1. Nobody has ever shown me data that #4 cylinder runs hotter than the other three.
        2. When you move the water feed from between Cylinder 1 and 2 to the rear to 4, what happens to 1 and 2? Do they run hotter now? Anybody got any real live data?
        3. We beat the tar out of the original test car (99 10AE) and put about 160,000 miles on it before the oil pump died and ended it. That morning we had it on dyno for tests and it made the same power as it did at 30,000 miles when we put the kit on it in 2004. (~130,000 miles on the kit.)
        4. We ran at least 100 dyno runs with EGT probes on all 4 cylinders and they were within the limits of error for the thermocouples. I would think that a cylinder that was running hot enough to warrant better/different cooling would have shown up there?

        Anyhow, Out of more than 650 kits around the world, there are probably less than 10 with rerouted water and the others are still running well with quite a few over the 100,000 mile mark now. Just my 2 cents.

        My favorite for radiator is either the KOYO or the Mishimoto. Two great choices.

        1990 with FFS Coldside. At least 260 WHP NON-INTERCOOLED