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92 sup 7mgte
57trim ct26 with factory manifolds (in and ex)
FMIC kit w/ pipes (3000 pipe may or may not stay, restriction will be cut off if staying)
AEM fuel pressure kit w/ some fattie injects
EMU black ECU with full rewire

I have an IAT with aluminum threaded bung(appears to be GM style) and I've been fighting myself over where to weld this fkr on, then I had an idea today.
The cold start injector port on the bottom of the intake manifold was going to be blocked off, but I found that the hole is actually only about 1-2 mm smaller than the aluminum bung for the IAT sensor....hmm. I could drill out the manifold hole slightly larger, then weld the bung into the cold start injector hole. boom, IAT sensor is in direct path of the incoming air right out of the throttle body. My thinking is the IAT needs to read the temp of the air going into the engine, not the temp of the air in the charge pipe before it gets a chance to pull in heat from the TB/manifold and whatever else could cause a change in air temp from the charge pipe to the manifold. Also, utilizing the hidden hole in the manifold would keep wires from dangling off my charge pipe and make it look a bit cleaner.

I realize there are plenty of other "Should I put my IAT pre-throttle body or post-TB" threads already, but the only real answers I'm really seeing for this is "I put mine pre-TB and it works". But wait, I see ford ecoboost engines and various other boosted engine manufacturers in my shop all the time with IAT sensors shoved into the plastic intake manifolds, post-TB.

EMU black manual states "IAT Sensor should be mounted close to the intake manifold, as the goal is to measure the air temperature in the inlet manifold. It is not recommended to mount the sensor in the intake manifold due to heat soak, i.e. the sensor being warmed by ambient heat from the engine itself."
Now I realize I'm being silly by trying to argue this, but the 7m intake and exhaust manifolds are on opposite sides, so I'm thinking the IAT sensor has a higher chance of heat soak due to being pre-TB as it is closer to the exhaust side. Then the intake manifold should be the better option due to how for away it is from the "hot" side of the engine bay.

Is there something I'm missing? Maybe turbulent air in the manifold giving the sensor bad readings? Or does this sound logical enough that it should "technically" work without issues?
 

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The EMU black manual is absolutely spot on about heat soak and falsely elevated IAT's because of it. The aluminum intake manifold itself gets hot because it's bolted to the cylinder head, and aluminum conducts heat very well. Which in turn warms up the sensor that's screwed into it. Some folks (including me) have tried phenolic spacers, insulating the IAT sensor, etc, all kinds of shit - it just doesn't work all that well.

Having played with all this crap myself back in the HKS VPC days;
On a 7M-GTE with a stock style intake manifold, the best bet is putting the IAT in the back of the 3000 pipe, right in between the two PCV fittings on the valve covers. I further improved this by replacing the VPC's metal temp sensor fitting with a polymer one that was some ice maker's replacement part. There was a thread about that here on SF, millions of years ago in the VPC days. Insulating the temp probe itself made a huge improvement. Not as critical with the GM IAT though, so that helps you out a bit.
I kept up with the idea by using a scrap of header tape to insulate the bottom part of the 3000 pipe where it bolts to the little 'T' bracket on the exhaust cam cover, and I ensured that the 3000 pipe wasn't touching the throttle body on the intake side, only the couplers on either side. If I wanted to get serious, I'd ceramic coat and header-wrap all the IC piping going over the engine, and I'd double down on heat shielding over the turbo too.

From a signal perspective, it's much better in a charge pipe because you have all that air mass passing over the sensor in one direction to keep things honest. In the intake manifold the reading will always be hotter than it actually is because of the heat soak issue.
 
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I appreciate the detailed response. I already have some wrap I planned on throwing on the manifold and down pipe, turbo has a blanket, and thermal tape is in the mail to wrap the charge pipe that cooks over the exhaust. Laying some thermal tape on the bottom of the 3000 pipe would be a good idea too. Thanks for the input, I'll probably drill a hole in the 3000 pipe like you said and hide the wiring in between the cam covers.
 

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I have the gm "fast acting" IAT sensor for my maft-pro

tried it under the hood and the heat soak was insane when you parked and started again in 5 min. especially with the sun beating on the hood of a hot car. I think the sensor also takes heat in through the wiring, something to keep in mind. I did not isolate the sensors metal mount when it was installed under the hood.

now I run it right after my intercooler. can't say that is the solution though because you can still get heat soak. like when the car sits on hot asphalt AND the sun is shining on the front end (imagine the sun heating the asphalt 8" below the intercooler/sensor)....same thing, massive heat soak.


now in either situation, running the car for X amount of time will bring the sensor back down to actual air temp. But in the first scenario, its much longer (several min VS 30 seconds) in my experiences

the biggest problem I run into is sitting at events in staging. the car soaks up a ton of heat, and has no opportunity to gobble up some cool air before a run, because you have to crawl the car to the line. so you start a pass with high af intake temps, then it briefly goes down before it swings right back up (3rd,4th gear full boost). in that scenario I don't doubt the sensors readings, obviously the car is hot... but the reaction time of the sensor is not exactly lightning fast so it helps to do anything you can to keep the sensor at the actual intake air temp to get real readings (if that makes sense)
 

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for IAT, you want it as close to the discharge pipe of your intercooler. That way at least you are keeping the engine heat from impacting it too much.
Also if you are standalone, be careful with any table that has IAT as an input as it might adversely affect fueling if you are heat soaked leading to a lean running engine.
 

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I didn't really consider the fact that the actual sensor body needs to cool down as well and not just the air passing over it before the readings are accurate. I could definitely see that taking a couple minutes since the engine is still warming it up on the connector side.
I had thought about trying to set up a open loop/closed loop timer for like 30 seconds on hot startup (if the ECU supports something like) that to help dull the effects of heat soak.
Maybe mounting the IAT very close to the throttle might not be such a great idea on the factory manifold design for my intended use of the car. A lot of driving around town, not as much track time.
Just when I think I've got things figured out, someone chimes in with some useful info to rain on my parade.
 

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Rez7m,

welcome to the information age where just about anything has an answer and most of the time, that answer is not congruent with the initial thought :)
 
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I was just being a little sarcastic, wasn't trying to come across as complaining. I really appreciate the input. Sometimes an outside perspective is all it takes to do something right the first time and not have to worry about doing it twice, or spending weeks on diag trying to figure out a problem that should have been avoided from the get-go.
 

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Rez7m,

we usually learn from others hence why these forums still have traffic with FB being a not even remotely close 2 place.

sidenote: I didn't think you were complaining?
 

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I am glad to see people seeking informed advise before attempting something that would be a waste of time and resources!

Forums are a good place to retain this info, learn from past mistakes. :)

Figgie, what about using a composite body IAT sensor vs a brass body IAT sensor.
IMO that would cool off much quicker and give faster actual air temp reading vs the brass...
 
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Or use a nylon insert similar to what us VPC guys use? It is a Home Depot part (Poly-pro brand WATTS PL-3004) with NPT threads on the outside, and you tap the inside to match the sensor threads. Mine is still in good shape after 18 years.

Al
 

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That works also.
Whatever it takes to separate the sensor from the large aluminum heatsink.
 

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put the sensor after the intercooler, the ecu should see the air temperature, not the temperature under the hood
 

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I am glad to see people seeking informed advise before attempting something that would be a waste of time and resources!

Forums are a good place to retain this info, learn from past mistakes. :)

Figgie, what about using a composite body IAT sensor vs a brass body IAT sensor.
IMO that would cool off much quicker and give faster actual air temp reading vs the brass...
My Opinion only,

It depends,

if the composite one has the temp sensor exposed such as the GM AIT, those are pretty quick overall. The mount should still be metal though for vibration longevity.
 
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