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Discussion Starter · #1 · (Edited)
Hey, I feel like my stock IATs are a little high. When it's ~92F outside, my IATs are like 140ish while driving (around 35-40mph). If I stop & idle, they approach 160F. This seems high to me, can anyone else confirm?

IF ANYONE DOESN'T FEEL LIKE READING THIS WHOLE THREAD:
With stock airbox, intake air temps were about 40-50F hotter than ambient when traveling at highway speeds. Checked and verified functionality of MAF, oil level, coolant level and everything was normal. Installed a Corksport SRI and now IATs are 2-10F above ambient!
 

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Hey, I feel like my stock IATs are a little high. When it's ~92F outside, my IATs are like 140ish while driving (around 35-40mph). If I stop & idle, they approach 160F. This seems high to me, can anyone else confirm?
I'll plug my scangauge in and get some readings. Probably not today as it's raining which'll throw off the measurements. I'm assuming you want a hot dry day for comparison (plenty of those around New Orleans, unless it's raining like today.)

What's your driving habit so I have a point of reference? City driving, or sustained highway?

Stock intake, SRI, CAI?
 

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Yeah that's like REEEEALLY high; mine when moving 40+ are ~1 degree higher than ambient.

At a light, when stopped for a few minutes and it's say 95+ degrees outside the hottest I've seen it go is up to 140, but not really any higher, but I also don't want it to get any hotter because getting moving again at that high temp is bad enough already.

But yeah, when moving they should be at least within 5 degrees of ambient, definitely not that high...
 

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Discussion Starter · #4 ·
I'll plug my scangauge in and get some readings. Probably not today as it's raining which'll throw off the measurements. I'm assuming you want a hot dry day for comparison (plenty of those around New Orleans, unless it's raining like today.)

What's your driving habit so I have a point of reference? City driving, or sustained highway?

Stock intake, SRI, CAI?
Yesterday was when I took notice when the alarm on my Ultragauge went off because of the IAT. I live on Long Island, temps were just over 90 degrees, maybe like 70% humidity and no wind.

I noticed it with around town driving. Speeds 30-40mph. Stopped for no more than 1 minute at a time, with driving about 8-10 minutes non-stop. So I was reading high temps while driving; then they jumped close to 165 while stopped.

Stock intake/airbox assembly, just a K&N drop-in filter which shouldn't make any difference.
 

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Discussion Starter · #5 ·
Also, my hood is un-insulated... there's no foam pad/insulation under it.

Not sure how much of a difference that'd make, but I'd imagine there's at least a slight one..
 

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Discussion Starter · #6 ·
Yeah that's like REEEEALLY high; mine when moving 40+ are ~1 degree higher than ambient.

At a light, when stopped for a few minutes and it's say 95+ degrees outside the hottest I've seen it go is up to 140, but not really any higher, but I also don't want it to get any hotter because getting moving again at that high temp is bad enough already.

But yeah, when moving they should be at least within 5 degrees of ambient, definitely not that high...
Wow... well then. Are you using a SRI/CAI?
 

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I just loaded up my logs from late last week and yea your numbers are hot... the hottest i see is 140f ( car sitting in the sun all morning cooking ) i think it was in the 80's that day and as I come to the end of the logging session (37 Minutes ) the IAT's are 118F = the IAT reading were dropping slowly to the actual ambient temp V's the start-up IAT temp

Ive always run a little hot on IAT, and right now my engine is being broken in + MS3 transmission = lots more heat in the engine compartment = Yours should be lower
 

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I assumed the stock box would run way cooler than my SRI, I still have the fiberglass mat under my hood; I just keep it there for the sake of less heat burning up my hood's paint.

Weird you're seeing such high temperatures.. fully stock box with just that drop in filter? Is the filter clean? Did you remove the lower section of the intake box or any mods of any sort? That just seems like waaay high.
 

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Discussion Starter · #10 ·
Appreciate the replies guys.

Air box is stock, filter is perfectly clean, oil level is full. My coolant is low because I just flushed it and need to add more, but still it's at the 'low' mark and I can't imagine it effecting IAT too much.

Could the sensor be bad and reporting false temps? Or maybe the UltraGauge isn't reading the sensor correctly?

Not sure what's going on here, but I'll keep an eye on it the next few days.

Thanks again for the help/suggestions.
 

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Yeah that's like REEEEALLY high; mine when moving 40+ are ~1 degree higher than ambient.

At a light, when stopped for a few minutes and it's say 95+ degrees outside the hottest I've seen it go is up to 140, but not really any higher, but I also don't want it to get any hotter because getting moving again at that high temp is bad enough already.

But yeah, when moving they should be at least within 5 degrees of ambient, definitely not that high...
+1, once moving your iat should be darn close to ambient. I watch this temp pretty closely at the track and running at redline for 30 mins mine stays the same as ambient and that's with sri. I would get to a mechanic and see if they get the same thing. Heat scares me!

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Discussion Starter · #13 ·
Thanks guys. And xcnuse, it is definitely my intake temp I'm looking at. But what's interesting is that the UltraGauge reports the IAT and ambient temp always within a few degrees of each other. So if the IAT is say 130, the gauge displays the ambient temp at like 126. But when I hit the 'Amb' (ambient) button on the climate control system, it reads the true outside temperature. So obviously the stock ambient temperature is not where the UltraGauge is getting it's ambient temp from...

Maybe I have to do a little more research to see if the UltraGauge is reporting sketchy values
 

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Thanks guys. And xcnuse, it is definitely my intake temp I'm looking at. But what's interesting is that the UltraGauge reports the IAT and ambient temp always within a few degrees of each other. So if the IAT is say 130, the gauge displays the ambient temp at like 126. But when I hit the 'Amb' (ambient) button on the climate control system, it reads the true outside temperature. So obviously the stock ambient temperature is not where the UltraGauge is getting it's ambient temp from...

Maybe I have to do a little more research to see if the UltraGauge is reporting sketchy values
I use Torque and bluetooth odb2 adapter. There's definitely a pid for iat. There's also one for air temp and it rarely reads the same as my inside cabin gauge. I've wondered why the difference but maybe there are separate sensors and the cabin gauge doesn't use ecu data?

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Discussion Starter · #15 ·
Are the sensors in the front bumper (literally right up front) for the ambient air temp that is displayed in the climate control system? Maybe that's different than the ECU sensors..
 

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Are the sensors in the front bumper (literally right up front) for the ambient air temp that is displayed in the climate control system? Maybe that's different than the ECU sensors..
Yeah, at least according to Mazda. I've never really looked

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Are the sensors in the front bumper (literally right up front) for the ambient air temp that is displayed in the climate control system? Maybe that's different than the ECU sensors..
There are two. Mine are zip-tied on right now. They're not much to look at.

I've noticed Torque shows temps within ~2 degrees or so of the head unit temp readout, so I'm pretty satisfied that both my car and Torque display fairly accurate temps.

I don't remember my IATs though...
 

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I can't speak for Mazda...

But on GM vehicles with an ambient temp reading on the mirror/display, they use a crazy pre-programmed set of code that estimates/calculates the "true" ambient air temp based on how long the car has been running(or not running), how fast it is going, it compares the ambient air temp sensor vs the intake air temp sensor.

For instance... If you've just shut your car down and come out and start it up 20 min later... normally the AAT sensor would read artificially high because of heat soak of the engine and radiator inflating the reading. It calculates the amount of time since the last time the car was shut down and uses the coolant temp vs ambient air temp(when it was shut down) readings in a table to display the correct "calculated" exterior temp on the display in the mirror.

It's pretty fawkin' wild... FWIW I wouldn't worry much about what the temp display reads anyway.


I'll add that if you're missing your hood "gaskets" and stuff, your stock intake won't be taking air in from outside, it will be taking it in from under the hood of the car because heat rises... meaning all the engine bay heat is raising straight upwards and out of the front of the hood, where it is recycled back into your intake.

at idle.

If it's still reading high while driving then it sounds like your sensor may be reading wrong, or you have a wire going to/from it with high resistance(possibly... I'd have to look up if higher resistance would make the reading go up or down... not sure if it's a linear or inverse voltage vs corresponding temperature type sensor).

I recommend start by unplugging the sensor at the front of the car, with key on use a DVOM to check the voltage and ground at the sensor's plug. If it's a 2 wire sensor, it will be a 5v and ground. If it's a 3 wire then one is ground, one is 5v, and the other will be the signal back to the PCM. Make sure it has 5v and ground.

You should be able to check the temp sensor reading when the car sits overnight, go out, look at the temperature of the sensor with the key in the ON position but engine not running. It should read same as ambient within 3-5 degrees at most difference.
 

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The sensors in the bumper are for the internal display and ac only ( i tested this by disconnecting both and confirming iat readouts as be available... Which they were) the iat readings are calculated at startup from the maf by the ecu and i believe it does that by measuring the voltage before any flow occures... The resistance being directly related to the ambient temperature.... How it adjusts after that i have no clue... Maybe correlation back to actual afr and measured lb/min? No idea really all i know is that the maf drives the iat temp reading

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The sensors in the bumper are for the internal display and ac only ( i tested this by disconnecting both and confirming iat readouts as be available... Which they were) the iat readings are calculated at startup from the maf by the ecu and i believe it does that by measuring the voltage before any flow occures... The resistance being directly related to the ambient temperature.... How it adjusts after that i have no clue... Maybe correlation back to actual afr and measured lb/min? No idea really all i know is that the maf drives the iat temp reading

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Amazingly complex! Wouldn't it be easier just to put temp sensors in different places? Guess that's why I'm not an engineer

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