IAT Sensor location question
10-02-20, 08:54 AM
#1
IAT Sensor location question
Just wanted to get some opinions on the best place to mount the IAT sensor on my single turbo modified FD. Some background - my FD is running a Link G4+ ECU, a single BW SXE turbo, Cosmo 13B-RE LIM/UIM with a GM DBW throttle body, using a custom fabricated TB to UIM adapter. That's how I got it from the PO, and that's why he mounted the IAT in the underside of the UIM, just behind the DBW TB & adapter. I'm using an XSPower IC core mounted in a stock-like configuration, with a custom fabricated cold air duct providing direct air flow to the IC. That IC is the largest core I found that I can cram in a SMIC location and still retain the battery up front.
Reason I'm asking the question is that IAT temps I'm logging are not dropping as quickly as experience indicates they should be after the engine is heat soaked, given all the other design factors. In similar setups, my experience is that IATs drop back to a their typical steady-state values (e.g., x degrees higher than ambient) within about 5~10 minutes of easy cruising after the heat soak condition. In my case, I have to cruise easy for at least 20~30 minutes to get the same level of IAT temp reduction
My take is that what I'm seeing is due to one or both of these factors: (1) Present IAT mounting location in the underside of the UIM just surrounds the sensor with too much metal/thermal mass, so it's skewing the measurement (i.e., readings are biased by the higher temps of sensor body and the metal it's mounted in, relative to air flowing past it), or (2) Maybe the sensor itself is a slow reacting type, and is not well suited for IAT measurement. The PO said that the IAT is a fast reacting open element Bosch sensor (which jibes with the Link calibration for the IAT), so I suspect the sensor itself is fine. The elbow to the DBW TB is silicone, so the closest to the inlet of the TB that I could possibly relocate it to would be the metal IC piping just before the silicone elbow. Would just need to weld on a bung, and extend my IAT wiring a few inches.
What do you all think - relocate the IAT sensor as described, shop for a better/faster reacting sensor, or do both?
Reason I'm asking the question is that IAT temps I'm logging are not dropping as quickly as experience indicates they should be after the engine is heat soaked, given all the other design factors. In similar setups, my experience is that IATs drop back to a their typical steady-state values (e.g., x degrees higher than ambient) within about 5~10 minutes of easy cruising after the heat soak condition. In my case, I have to cruise easy for at least 20~30 minutes to get the same level of IAT temp reduction
My take is that what I'm seeing is due to one or both of these factors: (1) Present IAT mounting location in the underside of the UIM just surrounds the sensor with too much metal/thermal mass, so it's skewing the measurement (i.e., readings are biased by the higher temps of sensor body and the metal it's mounted in, relative to air flowing past it), or (2) Maybe the sensor itself is a slow reacting type, and is not well suited for IAT measurement. The PO said that the IAT is a fast reacting open element Bosch sensor (which jibes with the Link calibration for the IAT), so I suspect the sensor itself is fine. The elbow to the DBW TB is silicone, so the closest to the inlet of the TB that I could possibly relocate it to would be the metal IC piping just before the silicone elbow. Would just need to weld on a bung, and extend my IAT wiring a few inches.
What do you all think - relocate the IAT sensor as described, shop for a better/faster reacting sensor, or do both?
10-02-20, 09:14 AM
#2
What IAT sensor are you using? I actually use the stock location. After much research and debate, it seems like it is a preference thing. Many will argue one way or the other. I'd rather use the stock location and tune for it. Works well for me. It is a fact that it does get heat soaked, but I figure it is an accurate representation of what is happening in the actual intake manifold itself.
My IATs drop literally as soon as I press the throttle. You need to see what kind of IAT sensor you have in there.
My IATs drop literally as soon as I press the throttle. You need to see what kind of IAT sensor you have in there.
10-02-20, 10:02 AM
#3
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+1 see what sensor you have and then try it in the IC pipe. i swear ive seen silicon elbows with sensor bungs in them too
if you have the ecu it might be tempting to put sensors on either side of the IC, and test that.
the stock Cosmo location was in the throttle body elbow, on the back.
if you have the ecu it might be tempting to put sensors on either side of the IC, and test that.
the stock Cosmo location was in the throttle body elbow, on the back.
10-02-20, 10:27 AM
#4
What IAT sensor are you using? I actually use the stock location. After much research and debate, it seems like it is a preference thing. Many will argue one way or the other. I'd rather use the stock location and tune for it. Works well for me. It is a fact that it does get heat soaked, but I figure it is an accurate representation of what is happening in the actual intake manifold itself.
Tuning for this IAT location in the Link is pretty easy, but in the end you're making assumptions about heat transfer that you hope are correct. In the FC's, Mazda mounted the IAT on the TB elbow just before the air enters the engine - much less thermal mass with heat soaked metal to deal with there.
That's exactly what happens with my FC turbo - and that's with the puny top mount IC. Agree I should take a look at the sensor, see what I got and probably replace it with a better faster reacting one. See if that changes what I'm logging and if necessary relocate the sensor to the piping just before the TB elbow inlet.
Last edited by Pete_89T2; 10-03-20 at 05:28 AM. Reason: fix typo
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