Is your IAT sensor hurting performance? Find out here!

TDCRacing · 03-28-2008

Ok so we decided to make a new thread about this.

We will be discussing how your IAT ( intake air temperature ) sensor may be hurting your performance due to it's response time/refresh rate.

The following posts are being taken from the previouse post and added to this post to try to get everybody back on track....And sorry if nobody like the way i did this...feel free to fix it or ask me to if needed. thanks

TDCRacing · 03-28-2008

Originally Posted by Reptile

Well, and here's another thing to consider. We need better IAT sensors. Not only for accuracy, but do you guys know what the normal refresh rate is? It's anywhere from 7-10 seconds. Voilant (sp?) sells an IAT sensor for the GTO's, and it's extremely expensive, but it's got an almost instant refresh rate, meaning that it's pretty much real time. Think about it. IF you're sitting in the staging lanes and everybody here is going to have heat soak issues. Once you step on that throttle, you're not getting 120* air into the engine, it's considerablly cooler.....Now if it takes 10 seconds to read the correct air, you're almost done, and you could possibly have made up .3 seconds in your quarter time if you could read better. At this point I honestly don't think it matters what type of filter you have if things aren't reading right.

Am I making sense? Maybe not.

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TDCRacing · 03-28-2008

Originally Posted by SyntheticShield

Now THERE is some useful information. Let me ask this then, the refresh rate is a function of the PCM, is it not? Is there no way to make the refresh rate faster in the PCM? Or does it require the sensor to do so?

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TDCRacing · 03-28-2008

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TDCRacing · 03-28-2008

Originally Posted by Reptile

I "think" that it actually has something to do with the sensitivity of the sensor.

There was a thread a couple years ago on KCPMC about a sensor, that you could solder in place of the old one.....actually rebuilding your IAT specifically.

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TDCRacing · 03-28-2008

Originally Posted by TDCRacing

huh....is there any way of testing this to make sure(not saying your wrong) ok lets say with the car on or running and looking at the scanner wait and let it sit until it reaches ambient temps (iat sensor out) and stick it in a glass of ice water (32*f) and see how long it takes for it to change and that could also tell you if it is accurate....would this be a good test???

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TDCRacing · 03-28-2008

Originally Posted by Reptile

I'm not sure about the whole water thing, but a can of compressed air turned upside down may be a good test. I may even do this tonight if I think about it.

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TDCRacing · 03-28-2008

Originally Posted by TDCRacing

....ok true about the refresh rate but what about something that has an accurate temp so we could check the accuracy of the iat also(that why i had mentioned the ice water because it will be 32*) any ideas??

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TDCRacing · 03-28-2008

Originally Posted by Reptile

Well, comparitively, I would only assume that if you had a digital climate control (which I do) then you could first compare the IAT temp with the climate head unit temp. They both run off of separate sensors, so you should know right off if they are close or not.

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TDCRacing · 03-28-2008

Originally Posted by TDCRacing

good point...when looking at the iat with the different intakes i never went under ambient temps according to my digital climate control vs. my iat gauge...so i guess it is not under accurate if you know what i mean lol (not reading under the temps that it actually is outside)

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TDCRacing · 03-28-2008

Originally Posted by TDCRacing

.....you know what i am going to go try that test with the ice water right now TO SEE HOW FAST THE REFRESH RATE IS and i will let everyone know how it turns out....the sensor is sealed so i dont imagine it will hurt it...the test will be with the car not running.... STANDBY!!!!!!!!!!

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TDCRacing · 03-28-2008

Originally Posted by TDCRacing

OK SO.....

The conditions:

69*F ambient temps (according to the digital cc)
IAT sensor removed from the intake tubing
IAT temps were at a steady 85*F for at least 10 sec before test was done
Test was done with a glass of ice water (32*F)

THE TEST:

With car turned off and key in the run position and the hpt scanner right in front of me and the IAT readings being a steady 85* for at least 10 seconds i submerged half of the sensor in whe cup of ice water ( not up to the actual connector even though it is sealed tight ) and the IAT temps on the gauge instantly started going down in at least 8 deg decreasements and took aprox. 16 seconds to reach 35* and stayed there contiunesly even at 35 seconds.At that time i stopped counting.Test was over.

OK well this is a 50 degree difference in temps. A 50 degree drop in temps is easily seen if you have an under hood open cone and have been stopped for any short period of time and then start driving again.This is not to say that the air that the IAT sensor is reading is not the temp that is being shown but rather a delayed measurement instead.

I dont think that there is a way to tell if the IAT sensor reacts quicker/slower to a majior temp change compared to a minor temp change.I would think that it's reaction time would be the same.

So yes the IAT sensor is delayed in reading the actual temps that are present.

Now a question: Could this delay purposely be made like this because the pcm would not be quick enogh to make instant changes like that? ex. to compensate for timng ect due to the cooler air temps.....

Just a thought

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TDCRacing · 03-28-2008

Originally Posted by Reptile

So now what can we assume by a better IAT sensor....perhaps an almost instant drop directly to say 32 degrees instead of over 16 seconds?

I'm not sure that the PCM wouldn't be able to keep up, keep in mind that what you see on the scan data is what the PCM is reading as input from the sensor. Given how fast it reads O2 values and degrees of timing, I would doubt it couldn't keep up with temperature change which isn't near as drastic.

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TDCRacing · 03-28-2008

Originally Posted by Reptile

Did you happen to count how long the interval was in between temperature changes to figure out the refresh rate?

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TDCRacing · 03-28-2008

Originally Posted by SyntheticShield

This is extremely good info guys. Great work and even better information. It times like this that my joy abounds even more that this community was formed.

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TDCRacing · 03-28-2008

Originally Posted by TDCRacing

1. Exactly!

2. Ok well not saying the GENERAL SPEED that the pcm is capable of is not keeping up with the temp changes (good example with the 02's) but more leaning twards it was not designed to,therefore getting a more accurate IAT may not matter.It may not be the IAT that is the problem after all.In other words it may be possible that the sensor is not the problem but how fast the pcm was DESIGNED to read the IAT temps may be lacking.

Or

...... I could be totally wrong and we may just need a better IAT sensor....Its a 15.00 part....It cant be made to meet to high of standards

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TDCRacing · 03-28-2008

Originally Posted by TDCRacing

Refresh rate was instant (not more than a second for sure).

As soon as the sensor hit the water it started decreasing.

Being that the refresh rate is so quick it almost seems like the sensor can only read so much of a decrease / increase in temps at a given time.

Funny how this thread started with wich intake to buy

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TDCRacing · 03-28-2008

Originally Posted by Reptile

Well, that being said...who's up for a little bit of R&D on some new IAT sensors. I can order them, solder the new thermisistor on and let people see for themselves. Ordering a $15 and paying $8 for shipping seems a little ridiculous, but ordering say 5 of them new, and acquiring some sensors for donation, even at a salvage yard they can't run more than $5 each...(only because I'm not COMPLETELY dishonest) lol

anyone up for it? I know I'm game.

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TDCRacing · 03-28-2008

Originally Posted by Reptile

. What we do know, is that it took at least 16 seconds for the sensor to show the exact temperature that we were shooting for, which in MY opinion, and hopefully others agree...is unacceptable. I'm on the return road after 16 seconds, and that could be precious time that could have been used for direct input.

Well, let's just say how about 5 people say they want one....Myself and I think Scotty included...along with TDCRacing....that leaves 2 people and I will PM them the total when I get things lined out. This way, I'm not breaking myself on buying these 15 bucks at a time, and the shipping would be more evenly distributed, plus counting the cost of finding a few sensors. A one time deal at first, then after we have some real testing we can go from there.....I can probably have these done in the next couple of weeks.

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