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Always fought this on SD tunes. It’s to the point in my “race cars” where I basically eliminate the MAT correction table and tune a little each track visit. Usually temps aren’t massively different so it’s not an issue.
Now I have a “daily” and it’s kick’n my *** again. This car has no IC so it makes it a tad worse/more sensitive.
I’ve got the car tuned great when it’s 85-95* or so ambient. But when I cruise to work in the mornings it’s 55-60*. So I hit AFR safety cutoff (1 point variance from target) every morning. If I add fuel so it runs well in the morning, in the afternoon when it’s 85-95* it’s super rich.
The issue is my IAT is reporting 105* even when it’s 62* ambient. It’s the GM sensor and it’s mounted in the plastic intake right behind the TB and has decent air flow. The turbo air inlets are in the fender and blocked off from the engine bay heat as well. The sensor reads ambient before I start the car so It’s not a sensor issue.
With no intercooler I don’t want to eliminate the IAT in the intake... At the same time I’d like to move the thing to the turbo inlet so I could cruise without farting around with leaning out every morning.
Not sure what the rest of your setup is but I'd move it as far away from external heat as possible while still being in the charge pipe. Is that possible with your setup?
I have a Holley sensor screwed into the charge pipe about 6" before the TB. It works great and no issues so far. I have it mounted on the short side bottom radius of the elbow.
The way I understood it was the plastic intakes didn’t “heat soak” like the alum charge piping or turbo housings. The turbos are in the fenders and are a straight shot to the TB. So I don’t believe the sensor is soaking up any engine bay heat. I guess the turbos themselves have to be sucking in hot air. Just not sure how to isolate them anymore than they already are. Here’s the setup... I used some molded ABS plastic to block off the bay heat.
I have a Holley sensor screwed into the charge pipe about 6" before the TB. It works great and no issues so far. I have it mounted on the short side bottom radius of the elbow.
Have you noted your IAT temps on cooler days? Are they actually close to ambient? Do you have an IC? AFR changes?
I have my screw in delphi IAT about 6 inches from the TB and maybe a foot from the blower outlet. No intercooler etc. The intake temps are usually around 120-140 cruising. 160+ in boost. I have no issues with afr, fuel trims stay pretty consistent, plus or minus 2%. I run it in sd + maf but when its forced into sd mode it stays consistent too. Ive never really seen an issue with an IAT hurting someone this bad vs cold start enrichment or poor injector scaling/tuning.
Not sure why your tune won't compensate for cooler IATs and adjust the fueling accordingly. I use the Holley system so that's the one I'm the most familiar with. Any way you can build a table in the tune that offsets the AFR based on an ambient air sensor? Not sure if your system will allow that or not.
Try to put it before the throttle body. Mine is in my up pipe about 4 inches before the throttle body. Moving it in front of the throttle body puts it more into the constant flow of air verses sitting behind the TB where the air flow can be blocked. This should help to prevent heat soak.
I have this problem. Solution: added a narrowband post turbine. Tune for track temps, let STFT take care of the rest.
exactly what I did. I messed with the bias table some and got it better but never to my liking, may revisit the bias when I have more time. But narrowband in the downpipe works perfect so far
I believe the MAT correction table would work fine... assuming it actually read ambient temps ever. Instead it’s reading 43-45* hotter than ambient. So when it’s cold out, it’s not adding fuel as it should.
As mentioned in my “race car” I just turn it off and compensate with closed loop fueling. But with there are temp swings of 40-60* between the morning drive to work and the drive home, that’s not really an option.
I actually think my closed loop fueling is part of the issue. It’s not fast enough to compensate for rapid acceleration when the tune/TEMP. is that far off in the morning. Was only 72* this morning but setting up the closed loop to turn off at anything over 40% TPS seemed to cure the issue. I’ll give it another go when it’s cooler. That stops the ECU’s ability to correct my WOT fueling though which is a bummer as well.
Mine is in my hollowed out maf housing before the throttle body. I feel like you’ll pick up more artificial heat with it inside the manifold. Especially right next to a heat soaked aluminum throttle body.
In for info.
Forced, I have an IC but have the same issue and my IAT is in the same location as yours.
I have played with the MAT correction graph with little success, as well as the bias table but may revisit that. I may first try to move the sensor infront of the TB as some have suggested.
For those who did the NB sensor in the DP, all on factory PCM's or MS3 (Goldbox) too? I think I'm out of inputs at the moment and not sure if where the STFT tables are or if there are any other than closed loop control.
I'm on factory PCM. I like my IAT in the manifold after my meth schnozzle. It tends to sit around 120º F so I just leave the timing at zero for the cells on either side and start pulling IAT timing at 140º and up....
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IAT tuning and sensor location dilemma 
