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Old 01-16-2009, 07:38 AM   #1
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Default IAT sensor location

Just curious about where you guys are putting the IAT sensor. I'm going to remove the AFM soon and the MSPNP instructions say to plumb it right before the throttle body but I got confused when I read some posts on here of guys talking about putting it elsewhere..
Thanks
-Ryan
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Old 01-16-2009, 08:16 AM   #2
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Mine (and I think the general location) is about 1/2way betweeen the TB & IC, a little closer to the IC. I know some have put it just outside the IC, and I think the consenus may be leaning towards this being the new desired spot due to heatsoak and whatnot.

Fwiw, I'll be relocating mine to right outside the IC for this reason..
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Old 01-16-2009, 09:35 AM   #3
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corky put mine close to the IC to avoid radiator heat-wind.
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Old 01-16-2009, 10:02 AM   #4
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if you're n/a then anywhere on the intake path.
if our boosted then after any cooling device.

in both cases each should be installed in a location where heat-soak will be less of an issue.

example, outside of the engine bay, just after the IC:
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Old 01-16-2009, 11:14 AM   #5
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Mine was in the engine bay, next to the TB and it heatsoaked like a mf. Moved it to the area similar to Brain's and it is perfect-o.
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Old 01-16-2009, 11:47 AM   #6
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Mine's right after the IC, near the headlight, pointing away from the engine. As far away as possible from any heat sources to avoid heat soak. Don't put it next to the TB as it will heatsoak bad.
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Old 01-16-2009, 01:49 PM   #7
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Have you guys actually had problems due to IAT sensor heatsoak? My non-Miata turbo has the IAT sensor in its factory location right behind the throttle plate, and while the IAT readings do go way up at idle on a hot engine, it cools right down once there is some air moving through the engine.
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Old 01-16-2009, 01:52 PM   #8
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I think maybe people are using a different reference to heatsoak than I understand. I have an open and a closed GM IAT/CLT sensor in front of me, and it looks like the closed loop sensor would get some serious misreads through its own case. I put it upside down in water and the sensor itself reflected water temp to a few degrees with the sensor tip completely out of the water. My next experiment involves ice and the same setup, since I have 2 meters with thermocouples, I'll freeze one in ice on the sensor and set the other one in water.

I haven't tried to put the open element sensor in water, they're not really made for that and would likely damage the sensor over time. The case of the closed-tip is very related to the temp of the surrounding metal, not the surrounding air. Running in a metal intake manifold (with coolant loops in the intake mani itelf like my GTX and a TB coolant anti-ice loop) screwed in is more or less completely wrong. There's a reason every OE car intake temp sensor is either properly isolated (AFMs are a good example) or are isolated AND open element (j body cavalier, most GMs, most japanese without flappy meter). My Daihatsu has a closed element sensor on the intake manfold, but its plastic and I haven't been able to modify its temperature with even a blowtorch on the intake manifold.


edit: Maybe we are all on the same page. Putting the IAT sensor on the plastic post-AFM pipe would solve manifold heat conduction-related errors.
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Old 01-16-2009, 02:11 PM   #9
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my AIT sensor would see over 140*F temps once i shut the motor off. that's heatsoak.

once moving the temps would drop but still stay high, they would actually drop in boost. that's heatsoak.

moved from that position, i see just above ambient anytime I'm not in boost, and the temperatures actually show a delta in boost....that's not heatsoak.
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Old 01-16-2009, 02:20 PM   #10
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geez, from what you guys are saying, its insane i haven't had more problems with this:
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Old 01-16-2009, 02:26 PM   #11
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Quote:
Originally Posted by N3v View Post
geez, from what you guys are saying, its insane i haven't had more problems with this:

Hey, uh, you can't just plug the PCV valve buddy. That's a good way to blow all the seals out of the engine and start a fire.
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Old 01-16-2009, 02:28 PM   #12
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Quote:
Originally Posted by Braineack View Post
once moving the temps would drop but still stay high, they would actually drop in boost. that's heatsoak.
This is with the GM sensor? It sounds like the sensor itself has too much thermal mass.

I am planning on using a Bosch part for IAT on my Miata -- figure B in this pdf.

Low thermal mass:
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Old 01-16-2009, 02:28 PM   #13
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Quote:
Originally Posted by patsmx5 View Post
Hey, uh, you can't just plug the PCV valve buddy. That's a good way to blow all the seals out of the engine and start a fire.
I've got an oil breather on the other side of the engine. Thats what the instruction manual I got with the kit said to do. Its been fine for about 6k miles so far.
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Old 01-16-2009, 02:42 PM   #14
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I would strongly suggest you vent it. I promise you are doing yourself no favors with it like that.

And FWIW, I ran an open element sensor near the TB and saw 50*F higher than ambient temps at cruise and higher at a stop. All from heatsoak.
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Old 01-16-2009, 03:02 PM   #15
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hmm, weird. the other day when it was about 28 outside it was reading around 36. I hardly ever have problems with it. When i'm idling it can go higher, but i'm sure the whole engine bay is getting hotter. as soon as i start moving, it drops way down again. usually it's around 6-10 degrees hotter than outside air.

And yeah about venting it, I'll probably vent that hole to an oil breather, then run the other one to a catch can. i feel like that'd work better.
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Old 06-28-2010, 05:40 PM   #16
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Quote:
Originally Posted by kday View Post
I am planning on using a Bosch part for IAT on my Miata -- figure B in this pdf.

Low thermal mass:
Did you ever fit that sensor? I was thinking of using it also to solve my heat solve issues. I'm not too fond of the o-ring though.

Last edited by WestfieldMX5; 07-04-2010 at 01:38 PM. Reason: typo
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