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Discussion Starter · #1 ·
Hello, where is the best spot for an Intake Air Temperature sensor on the 302?

Some people say it should be in the intake air tube, others say the upper intake plenum, others say the lower intake manifold. The stock location is on the cylinder #5 runner in the lower intake manifold, but I've read that heat soak will affect the sensor. I have a phenolic spacer and expect the upper intake is going to be a lot cooler than the lower. Should I weld a bung to the intake air tube and position the sensor close to the throttle body? Or should I install it down in the lower manifold stock location? Or the upper manifold somewhere? Or does it even matter since I'll be using a Microsquirt ECU? I assume I can calibrate it in the software...

Help appreciated, thanks.

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You should use the stock location for your ECU application. The 93 mustang ecu for example is programmed to take the location into account. If you're not retuning you should use the stock location. If you're retuning it doesn't really matter because you're going to tune it based on location. A 94/95 ecu has a lower temperature threshold before it starts pulling timing and affecting fuel because it's in the intake tube. Putting it in the intake tube with a ecu that is programmed for it in the manifold will result in the ecu not pulling timing correctly or compensating fuel currently because the sensor has been moved
 

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Discussion Starter · #3 ·
Okay cool. Since I don't even have a stock computer I guess it's optional. This is an EFI+turbo conversion and the motor was originally carbureted. I just grabbed a manifold and a couple other parts off an old LTD Crown Vic 5.0 EFI donor car at the junkyard. I planned from the beginning to use a standalone engine management system(Microsquirt) and tune it completely from the ground up, so I didn't even bother getting the stock EEC. Thank you.
 

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I would put it in the intake track then. Just know your temperature settings will be significantly lower than it would be in the intake manifold.
 

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Discussion Starter · #5 ·
I was thinking that too, because at least that way the temperature reading would be more consistent with the actual air temp, without the heating-up effect the lower manifold experiences as heat soaks into it from the engine, and into the sensor.

With the sensor mounted down in the #5 cylinder intake runner, it seems to me like the computer would always register the air getting hotter along with the engine as it heats up. But what do I know? Obviously Ford didn't think it was a big deal by placing it there, and the sensing element is probably pretty isolated from the sensor body anyway.
 

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In the #5 runner is the worst place for it based on what I’ve seen in logs.

If you move it to the upper plenum that’s a much better spot. It’s not super critical on n/a megasquirt and microsquirt based stuff, but much more important if you’re boosted.
 

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Discussion Starter · #7 ·
In the #5 runner is the worst place for it based on what I’ve seen in logs.

If you move it to the upper plenum that’s a much better spot. It’s not super critical on n/a megasquirt and microsquirt based stuff, but much more important if you’re boosted.
Oh ok, I appreciate that.
 

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In the #5 runner is the worst place for it based on what I’ve seen in logs.

If you move it to the upper plenum that’s a much better spot. It’s not super critical on n/a megasquirt and microsquirt based stuff, but much more important if you’re boosted.
I respectfully disagree. It doesn't matter where it is, boosted or not. What matters is what you do based on temp. If you start pulling timing at 100 degrees with it in the intake you would do it at say 160 degrees in the manifold. If you compare A9L and T4M0 aic tables that is exactly what Ford does.
 

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Only matters if you are going to use it to pull timing. I really don't know the right answer of where. Leech motorsports has a video on it.
 
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I respectfully disagree. It doesn't matter where it is, boosted or not. What matters is what you do based on temp. If you start pulling timing at 100 degrees with it in the intake you would do it at say 160 degrees in the manifold. If you compare A9L and T4M0 aic tables that is exactly what Ford does.
If the sensor is in a heat soaked piece of aluminum then it sure matters. I am sure they do have a spark correction for mat.

I’m interested in getting a reading of the intake air temp, not the lower manifold.
 
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The air in the intake manifold gets heat soaked too. The temp of the air in the intake is not the same as the manifold. Slow air movement will heat soak more than fast air movement. This is why the location doesn't matter, heat soaked or not. What matters is what you do with the data and at what temp. There was a good write up on efidynotuning about this but it's gone after he lost the forum database.
 
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I doubt any kind of “heat soaked” air will be around when you’re at WOT, which on a boosted application is really when I use MAT to retard timing. If you want to keep it in #5 that’s all fine and dandy, but it’s not ideal and not what I would recommend

Pretty much no car that I currently know of which is currently manufactured, or has been in the last 10 years places a iat on the runner closest to where a coolant crossover is. Most are in the pipe before the tb, or very close to it if not integrated into the maf.
 

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Engine Masters did a test. Then air is moving fast enough it heats very little if at all going through the intake.
 

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When you're at wot the air passing over the sensor in the intake manifold is stable and accurate simply with a higher value because it's in the manifold. Under boost, cruising or idling the air in the manifold is still picking up heat so the air is always heat soaked to some degree. I tend to trust someone who has tuned hundreds if not thousands of cars when he says it doesn't matter as long as you compensate correctly. I have tuned cars in both locations, either location workrd fine for me so his experiences correlate with mine. While i don't doubt manufacturers moved all of them to the intake tube, I would be willing to bet integrated temp sensors in a MAF is more about cost savings and simplicity than anything else. Why use two separate sensors and connectors when they can use one. To be clear, i'm not advocating for it in the intake manifold. There is just no point moving it for the sake of moving it and both locations work fine as long as it's tuned for that location
 

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Only a KB setup needs an IAT sensor in the lower as there's not many other places to put it after the S/C. My GT500 has one before and one after the S/C.
 

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I would put it pre-TB where you have drawn an arrow. Or tap the side of the intake manifold in the back just after the throttle body and install it there.
 

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Discussion Starter · #17 · (Edited)
This is why I come here. Great info.

While I don't know how much the sensor's inner sensing element is affected by the temperature of its housing, I'd rather not take the chance, and just install it in the upper intake manifold or air tube and be done with it. At least it won't be subjected to such a wide temperature swing. All things else being equal, and having no limitation forcing me to keep it in the stock location since I'm tuning anyway, I'll just place it in the upper area.
 

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Why not test the sensor itself? Measure resistance and slowly heat the body of the sensor with a pencil torch, or possibly a small heat gun while covering the very tip of the sensor.. See if the body does get heat soaked..
 

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Discussion Starter · #20 · (Edited)
Well I think I may have changed my mind about this again.

Why not test the sensor itself? Measure resistance and slowly heat the body of the sensor with a pencil torch, or possibly a small heat gun while covering the very tip of the sensor.. See if the body does get heat soaked..
I just checked my sensor out and the resistance looks right but I don't have a great way of blowing air across the tip in a controlled manner while heating the body up to simulate conditions installed in the lower manifold on a running engine.

Although, one thing I noticed, the sensing element is situated pretty well away from the brass body and supported up into the air stream by tiny prongs not likely to transfer much heat. Especially when you consider how much airflow this thing probably sees. The insulating separator is plastic. It looks like a pretty good design that wouldn't heat soak much...

Leech motorsports has a video on it.
I watched his video and he made good points about the location of the sensor affecting the A/F ratio on warm engine restarts. Basically the sensor cools off really fast if it's located in a cold area, even if the engine itsself is still hot, so the computer commands a richer mixture as a result of seeing this cold air temp when it's not really needed. I don't really like rich starts. I would like my setup to run as efficiently as possible.

And finally, it will save myself the work of tapping or welding a bung to install it in a different location. I'm thinking it's just not worth the effort. It doesn't look like I have to worry about any great differences in readings, or at least anything that can't be compensated for in my tuning adjustments.
 

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