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IAT Location POLL - Before TB or After


trwebb26

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I've done the search and it seems like there are mixed opinions in previous posts. It seems like most people say they mount it in the cold start hole, but all the pictures of engine bays I see have it before the throttle body. Right now I'm leaning toward the cold start hole. Where do you have yours mounted and do you think it makes a difference whether it is before the throttle body or after.

 

Thanks!

Tim

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I mounted mine in the cold start hole. the Haltech manual states that you should mount it as close to the head as possible...I felt that thats about as close as you should, or could really get. plus the fact that there is a hole there already...it just made sense to me. the car is not running yet, so I cannot tell you if i've had any problems. hopefully I will know very soon though.

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Put your IAT sensor wherever you want to put it. The difference of a couple of inches between just before the throttle body and the cold start hole will not make any difference in performance. Keep in mind that you are going to be tuning your engine, so your tune will compensate for the slight difference in temperature readings. I put mine in the intercooler pipe, just before my water injection. I do know that if you run water injection before the sensor, the readings are not accurate at all.

-jeremy-

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  • 1 month later...

I was curious about this too. I have mine mounted in the cold start vavle hole like alot of people. I think the major difference in the location, even if it is only a couple inches is the amount of heatsoak your gonna get in the manifold. This isnt such a big deal when driving around. But after sitting for a bit, waiting in the staging lane etc, you are going to see higher temps then if it was in the i/c pipe.

 

Whether or not this really matters I dunno, thats what im asking. Seems to me the most isolated the sensor can be relative to manifold temperature would be the best. Thats why I always wondered if the i/c pipe was better

 

Another question, just how well isolated is the sensor element? Is my concern even an issue?

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Hey Guys,

 

I know you flamed me for saying this last time we talked about this, but I mounted my sensor on the "intake" the turbo.

 

You laugh, but I have never had a problem with heat soak, and the car has never shown any problem with the way its tuned.

 

When the car comes out of storage I'll try the locations your using and let you know what differences I find.

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I ended up putting it in the cold start hole. 6 Reasons:

1) I won't have to move it when I go turbo.

2) I figure the heat soak will be minimal... aluminum intake manifold through the brass to the "free air" part of the sensor - and only when there isn't a serious rush of air running over it at cruising or WOT to cool it off.

3) I think that good tune with the wideband will take care of any residual heat soak that I do end up with - at least on the average.

4) Wiring is nice and clean.

5) The bigass hole is already there - might as well fill it up.

6) An easy NPT tap (not like those godawful ones in the thermostat housing). I've said it before and I'll say it again - a blind, tapered tap in aluminum is a horrible job.

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You want the sensor where it will get the most accurate reading of intake air temperature. With only one sensor, the best loaction is in the intake plenum somewhere in the middle. This way you will get somewhat of an average temp across all runners.

 

As far as heat soak, you will have heat soak no matter where you put the sensor. The MS will compensate for temperature change in the intake (uh, that is what the IAT sensor is for). So putting the sensor in a place where it will inform the MS that the intake temp is high is important. The cold start injector hole is a good place, and so is the hole that is centered in the plenum, that is where I put them.

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Not MS specific here, but on my SDS I have tried a few positions with varying results. First position was very close to the brake booster vacuum line and I had massive heat soak issues, and very inconsistant A/F readings because of that. Temperatures would be ~50-60C on a 15C ambiant day if I was sitting. Under highway cruise they would move to the 35C range.

 

Since then I have moved it to the cold pipe just before the TB, and the results are very positive when compared to the origional position. AFR's are consistant, and heat soak really isn't an issue anymore. I'd recommend a similarly isolated position.

 

Also, moby smells funny.

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How inconsistent were you AFR's drax? This is VERY VERY interesting me me and you have got my attention. As i mentioned eariler i think heat soak is the problem in the manifold.

 

I have been tuning with my LM1 and I have choppy afr readings. Perhaps this might be a contributing factor? Do you have charts of your afr readings?

 

Here is a link to mine:

http://gallery.voodoo-people.com/album658/logmap?full=1

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For those using a lexan throttle body spacer and a 240SX throttle body, the spacer is a good and easy place to put it, since it's right behind the throttle body and won't suffer from heat soak at all. You can seal it perfectly with an 0-ring. It might not give the most accurate reading because the air in the intake will be warmer based on the intake being hot, but most ecu's only use it as a reference anyway.

 

1846560IAT.jpg

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Ross at SDS recommended moving mine from the intake to the IC piping. His position was that with the non-crossflow head, there is significant heat transfer to the intake casting when you are sitting or running slow. This can cause driveability issues in the areas where it is really noticeable, slow speed idling around or sitting in traffic. I agree with him that the IC pipe mount responds more quickly to changes in temperature, because of the reduction in hot metal surrounding the sensor.

Also, if you are going to spray alky or N20, the sensor has to be upstream of the injection. Made the IAT position pretty clear for me. Most automakers position IAT before the throttlebody, also.

 

 

Doug

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Also, if you are going to spray alky or N20, the sensor has to be upstream of the injection.

 

MSnS ignores IAT once water injection is started until you drop below a set psi. I am not sure what that means fully, does it just ignore IAT so water injection doesn't turn off based on IAT or does it actually ignore it for fuel correction. I believe the former, anyone else looked into it further?

 

Also, moby smells funny.

 

Now, how did you slip that in there without an edit showing up??? I could swear there was no other reply after z-ya :bonk:

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