How IAT sensor position affecting temp
Thread Starter
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From: Lebanon
Cls63 & C32
How IAT sensor position affecting temp
I have changed the position of the IAT sensor on my new built engine from Y pipe to the surge tank, i noticed that the IAT still increasing after i take out my feet from the throttle when going wot like 2-3 seconds(from 140/145F to 160/165F) then start dropping, did anyone know why? anyone who changed the position of the sensor noticed similar thing?
and does it affect the temp at wot (lower or higher IAT)?
and does it affect the temp at wot (lower or higher IAT)?
Last edited by Robert AMG; Sep 9, 2012 at 05:38 AM.
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From: Porter Ranch, CA
E55, CTS-V Wagon, Duc 1098R
Are you getting direct measurements. If not that is probably the time constant of the OBD updating especially if you are taking more than 4 measurements at a time. Can you post the actual data?
Thread Starter
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From: Lebanon
Cls63 & C32
maybe because the sensor is now up top the cylinder and valves.
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From: Porter Ranch, CA
E55, CTS-V Wagon, Duc 1098R
Where exactly did you put it since the sensor is directional an needs some air velocity to work fast. Is it in the surge tank tube or in the surge tank plenum box.
Thread Starter
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From: Lebanon
Cls63 & C32
I am re-posting cause those AIT are making me nerves when i take my foot from the throttle, it is increasing my starting AIT runs, i attached a pic where the AIT sensor is (driver side surge tank) and a video on the dyno where you can see how the AIT rise when i take off my foot. i need to solve this issue.
http://youtu.be/QgzrK1nUgkg
http://youtu.be/QgzrK1nUgkg
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one car at a time
This is understandable since you changed the location of the sensor. Once you take your foot off the throttle there will be very little air flowing over the sensor and the tanks are acting as a giant heat sink, thus you will see your IATs increase for a bit.
I would either not worry about it or put the sensor back in the factory location.
I would either not worry about it or put the sensor back in the factory location.
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The factory location is long gone, along with the lower intercooler. I see the airflow sensor and the AIT both in side of plenum. How does the car run?
If it runs good, then I would leave it where it is. There really is not any better place after the intercooler to place it, and you dont want to position it before.
Do you still have the bypass under SC? I assume you gutted the stock intercooler, or fabricated a new one correct.
If it runs good, then I would leave it where it is. There really is not any better place after the intercooler to place it, and you dont want to position it before.
Do you still have the bypass under SC? I assume you gutted the stock intercooler, or fabricated a new one correct.
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From: Porter Ranch, CA
E55, CTS-V Wagon, Duc 1098R
It looks like you picked a spot that was convenient but the worst for flow. The sensor is directional and you have it rotated 90 degrees off and in a dead spot in the intake. Where its positioned now, the clips should be pointing side to side not top to bottom. For the sensor to work properly now, you need flow to occur along the same line as the AMG name on the surge tank when in fact its mostly flowing across it. Looks like it needs to be placed on the back of the surge tank with clips top to bottom or on top of the tank with the clips parallel to the amg name. The stuff you are seeing is cam overlap and regurg in the tank under vacuum at high speeds. It is not heat sinking since the physics would not let the temps to change that fast.
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What others said, heatsoak and location. I'm surprised your timing does not get pulled even further. Car sounds good though. What was ambient during the dyno?
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From: Lebanon
Cls63 & C32
thanks guys for all replies, good knowlegde.
there is no place in the original location and i want to install a water weth kit with dual nozzles, one on each pipe before the surge tank so i need the AIT sensor after the nozzles. and i can't leave it, it is making my AIT higher.
the car run good, no by pass, i cutted and welded the C32 intercooler to let it fit under the V8 SC and in the small location i have at the rear.
i'll try tomorrow to change the direction of the sensor(clips), if nothing changed i'll change the position of the sensor like you mentioned, but what i am 100% with you is the increasing in ait is cam overlap and regurg under vacuum and if i want to solve this i'll have to put the sensor not above the runners so it will not be direct to flow so i am confused!
ambient was like 88-90*F. the timing will not get pulled more cause when WOT the AIT went from 120 to 150F not more, but when vacuum the ait went to 180F.
This is understandable since you changed the location of the sensor. Once you take your foot off the throttle there will be very little air flowing over the sensor and the tanks are acting as a giant heat sink, thus you will see your IATs increase for a bit.
I would either not worry about it or put the sensor back in the factory location.
I would either not worry about it or put the sensor back in the factory location.
The factory location is long gone, along with the lower intercooler. I see the airflow sensor and the AIT both in side of plenum. How does the car run?
If it runs good, then I would leave it where it is. There really is not any better place after the intercooler to place it, and you dont want to position it before.
Do you still have the bypass under SC? I assume you gutted the stock intercooler, or fabricated a new one correct.
If it runs good, then I would leave it where it is. There really is not any better place after the intercooler to place it, and you dont want to position it before.
Do you still have the bypass under SC? I assume you gutted the stock intercooler, or fabricated a new one correct.
It looks like you picked a spot that was convenient but the worst for flow. The sensor is directional and you have it rotated 90 degrees off and in a dead spot in the intake. Where its positioned now, the clips should be pointing side to side not top to bottom. For the sensor to work properly now, you need flow to occur along the same line as the AMG name on the surge tank when in fact its mostly flowing across it. Looks like it needs to be placed on the back of the surge tank with clips top to bottom or on top of the tank with the clips parallel to the amg name. The stuff you are seeing is cam overlap and regurg in the tank under vacuum at high speeds. It is not heat sinking since the physics would not let the temps to change that fast.
ambient was like 88-90*F. the timing will not get pulled more cause when WOT the AIT went from 120 to 150F not more, but when vacuum the ait went to 180F.
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From: Porter Ranch, CA
E55, CTS-V Wagon, Duc 1098R
One option for you to consider is putting the meth jets right after the supercharger but way before your new intercoolers. This will help with mixing and measuring your IAT. It's probably going to be much more effective as well since I think you will have a hard time getting even distribution injecting them into the surge tanks. Even putting them into the feed tubes as far back as possible will be good since you will easily flash the meth for sure.
If I'm not mistaken, Bramage tried this with a hollowed out intercooler an got good results.
Just a thought...
If I'm not mistaken, Bramage tried this with a hollowed out intercooler an got good results.
Just a thought...
Thread Starter
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From: Lebanon
Cls63 & C32
Water meth kit installation:
SC, IC then nozzles in the feed pipes before surge tanks and AIT sensor in the surge tank, like that the air will be cooled with IC after then more cooled with meth before entering surge tank, then AIT measuring.
returning to the main post i changed the direction of the clips nothing changed, so now i'll have to change the location of the sensor but i am confused about the place!!
SC, IC then nozzles in the feed pipes before surge tanks and AIT sensor in the surge tank, like that the air will be cooled with IC after then more cooled with meth before entering surge tank, then AIT measuring.
returning to the main post i changed the direction of the clips nothing changed, so now i'll have to change the location of the sensor but i am confused about the place!!
Thread Starter
Joined: Jan 2009
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From: Lebanon
Cls63 & C32
i am now with the V8 SC on the 3.72l V6 engine without the bypass.
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E55, CTS-V Wagon, Duc 1098R
The other question/thought I had was where do you have the crank case recirc? I am wondering if the heat is coming from that since it is happening once the throttle is shut and I am guessing you have it plumbed into the surge tank. You might want to consider testing it again with it venting to atmosphere and the surge tank plugged since it could be a source for this heat as well.
Thread Starter
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From: Lebanon
Cls63 & C32
I think you should be able to tell from your logs if you need it. Specifically if there is still pressure on the MAP sensor when you are seeing the heating that could be a sign but I am not sure you would see it.
The other question/thought I had was where do you have the crank case recirc? I am wondering if the heat is coming from that since it is happening once the throttle is shut and I am guessing you have it plumbed into the surge tank. You might want to consider testing it again with it venting to atmosphere and the surge tank plugged since it could be a source for this heat as well.
The other question/thought I had was where do you have the crank case recirc? I am wondering if the heat is coming from that since it is happening once the throttle is shut and I am guessing you have it plumbed into the surge tank. You might want to consider testing it again with it venting to atmosphere and the surge tank plugged since it could be a source for this heat as well.
what do you mean by crank case recirc? is it the valve cover vent pipe that is connected to the TB, if it is i plumbed it before the SC after the TB.
