IAT Sensor - Where is yours?
Joined: Nov 2007
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Originally Posted by 1SlowSi' timestamp='1333463206' post='21570791
So is the point of this thread stating that the stock IAT is slow and the location is inaccurate with heat soak or just that it's slow in being able to make those rapid changes needed for racing?
Sure it may not be as extreme, but the issue is still there.
Joined: Nov 2007
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Accurate within reason. I.E. ACTUAL IAT = 100 but IAT sensor reading +/- 5 deg. I believe that is accurate enough for me.
Thread Starter
Joined: Sep 2004
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From: Tampa, FL
Yes and no. It's probably accurate if you dipped it in a pot of water and logged the temp it outputs, but the issue is how accurate it is over a period of time under changing conditions. That's what this thread is about.
Registered User
Joined: Jan 2008
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From: Lakeland, Florida
my main question would be:
when honda moved the intake temp sensor to the intake tube on rsx's and 2006+ s2000's, what were the motives? and why did they leave it in the mani on others? after all the years of having it near R3 or R4 on the intake mani, why the sudden change?
obviously if a car is tuned with a AIT sensor wherever it may be, it is advantageous to leave it where it is so you dont jack the readings/your tune up, right? but if you were going for a new tune, why not move it to just in front of the TB?
I think honda had it right though in the DD instance of air temp monitoring though, because you want the temp of the air as close as you can get to where it is about to be combusted.
FWIW:
the overall issue is not where to mount the sensor to get away from the 9 million degree intake mani, it is heat transfer through the head and the coolant lines. if there was zero transfer through the head, this wouldnt even be brought up.
there needs to be a viable solution to that problem. like a composite gasket that will not transmit heat but yet not warp like the hondata/P2R gaskets have been shown to do. maybe a pioneer with some money and free time can create this gasket for us. cause then, the intake would no longer be heat soaked and the question wouldnt be, "where do you mount your AIT sensor" but rather, "where do you guys wanna hang out" since this will no longer be on our minds, plaguing us forever.
think about it, if the mani was totally disconnected and all we did was measure the temp of air flowing through the tb and out, there is no way it would ever be more than 15 degrees over ambient with a proper IC,AC at any time; sitting after a hard drive for 10 minutes or fresh start in the AM, the temps would never get transferred from the 190+ head to the intake.causing it to warm the internal air like a literal oven.
maybe the solution is a new intake manifold material altogether? carbon fiber reinforced nylon composite would do the deed nicely.
btw, love this thread.
when honda moved the intake temp sensor to the intake tube on rsx's and 2006+ s2000's, what were the motives? and why did they leave it in the mani on others? after all the years of having it near R3 or R4 on the intake mani, why the sudden change?
obviously if a car is tuned with a AIT sensor wherever it may be, it is advantageous to leave it where it is so you dont jack the readings/your tune up, right? but if you were going for a new tune, why not move it to just in front of the TB?
I think honda had it right though in the DD instance of air temp monitoring though, because you want the temp of the air as close as you can get to where it is about to be combusted.
FWIW:
the overall issue is not where to mount the sensor to get away from the 9 million degree intake mani, it is heat transfer through the head and the coolant lines. if there was zero transfer through the head, this wouldnt even be brought up.
there needs to be a viable solution to that problem. like a composite gasket that will not transmit heat but yet not warp like the hondata/P2R gaskets have been shown to do. maybe a pioneer with some money and free time can create this gasket for us. cause then, the intake would no longer be heat soaked and the question wouldnt be, "where do you mount your AIT sensor" but rather, "where do you guys wanna hang out" since this will no longer be on our minds, plaguing us forever.
think about it, if the mani was totally disconnected and all we did was measure the temp of air flowing through the tb and out, there is no way it would ever be more than 15 degrees over ambient with a proper IC,AC at any time; sitting after a hard drive for 10 minutes or fresh start in the AM, the temps would never get transferred from the 190+ head to the intake.causing it to warm the internal air like a literal oven.
maybe the solution is a new intake manifold material altogether? carbon fiber reinforced nylon composite would do the deed nicely.
btw, love this thread.
Registered User
Joined: Jan 2008
Posts: 1,967
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From: Lakeland, Florida
thought of this today:
what would the implications be of moving the ait sensor to a location just off the TB in terms of messing with your tune?
i mean, it would be no diff than if someone suffering from high intake temps ran a snorkel to the front of the car to drop temps and then kept on with his same map right?
the ait would no longer be heat soaked in the manifold, but my next question would be, will the non-heat soaked ait sensor jack with your idle since it is no longer being super heated and is reading cooler than the air trapped in the mani?
upon accelerating or cruising of any sort, your temps would be more accurate.
the 06 ap2's run it this way as well as modern K-series too.
so, do you think moving it to just in front of the tb will effect how the car runs/performs?
thoughts?
what would the implications be of moving the ait sensor to a location just off the TB in terms of messing with your tune?
i mean, it would be no diff than if someone suffering from high intake temps ran a snorkel to the front of the car to drop temps and then kept on with his same map right?
the ait would no longer be heat soaked in the manifold, but my next question would be, will the non-heat soaked ait sensor jack with your idle since it is no longer being super heated and is reading cooler than the air trapped in the mani?
upon accelerating or cruising of any sort, your temps would be more accurate.
the 06 ap2's run it this way as well as modern K-series too.
so, do you think moving it to just in front of the tb will effect how the car runs/performs?
thoughts?
Thread Starter
Joined: Sep 2004
Posts: 4,894
Likes: 9
From: Tampa, FL
Originally Posted by Legion
It's one of those "you can't have your cake and eat it too" type of situations. Thermistor response times are rated by their time constant. The smaller the thermistor, the smaller the time constant. Also, any barrier between the thermistor and the air is going to slow the response time even further.
It's a simple concept really - you want the air as close to the center of the thermistor as possible to achieve fast readings. The toss up is that the thermistor is very sensitive, and exposing it leaves it vulnerable to handling damage.
So the Honda IATs not only use large epoxy filled thermistors, but they have an (insulating!) layer of plastic over them that further kills response.
It's a simple concept really - you want the air as close to the center of the thermistor as possible to achieve fast readings. The toss up is that the thermistor is very sensitive, and exposing it leaves it vulnerable to handling damage.
So the Honda IATs not only use large epoxy filled thermistors, but they have an (insulating!) layer of plastic over them that further kills response.
I haven't forgotten about this. Turns out that answer to this problem might have been staring us right in the face the whole time. If I have time tonight, I'll try to sit down and do a write up of my findings. But let me ask this question - what do you think would happen to the response time of the IAT if we were to strip away the plastic housing covering the actual thermistor of the sensor?
Joined: Oct 2002
Posts: 8,044
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From: South Florida
i still dont understand how fast people want this sensor to react. when i am cruising, it reads a temp, if i let off the gas and compression brake, iat temps immediately start to rise. if i get on the gas and get some fresh air flowing in there, temps immediately start to drop. we are not race car drivers, it works fine for a street car.