Intake Air Temp reading 6°F too high. Is this a problem?
 

The Intake Air Temperature (IAT) on my Z is reading about 6°F too high. I let the car cool overnight with the hood open and then compared IAT, ambient temp on the dash, and two digital thermometers. Both DTs and the dash said 61°F; the IAT, using a ScanGuageII, was 67°F.

Will this cause any problems?

I can't find an OBD Mode/PID for bank 2 IAT. Would swapping MAFs (to see if the temp sensor in bank 2 is reading closer) cause any harm?

Car is an '09 Touring 7AT. DD with 21K miles.

If you were to correct the 6* difference, what are your expectations in performance? Personally, I don't think its worth the effort because there is little to gain for a relatively small temp difference i.e. minimal effect on A/F ratio.

I really don't have any expectations of performance gains (other than maybe getting closer to proper AFR). Mainly just wondering if this is something to be fixed or ignored. I'll put you in the "ignore it" column.

Do you know if it would cause any problems if I swapped the MAFs? I can't see any problems but I don't always grok modern engine control and would like to get some input from someone that does.

Are you able to do any data logging or monitor your A/F ratio? If so, see if your afr is outta whack. Under hard acceleration it should be around 13 for na. Cruise should be around 15. Again, I wouldn't be concerned about chasing down that small of a difference. Also, it may be smaller than you think if the monitoring/iat sensors are out of calibration by a couple of degrees.

My ScanGuageII is able to monitor AFR via OBD. I'll give that a try. Thanks for the tip.

It doesn't appear to be causing any problems but I thought I'd see what others had to say about it in case it could cause long-term damage. Plus, I was an Instrument Tech before I retired and can be a bit obsessive about gauges reading correctly. :)

how are you sure what the actual temperature is? won't intake temperature be warmer than ambient? these are two different sensors and one is just for the clock.... does air fuel ratio adjust based on temperature anyways?

As stated, I had two digital thermometers and the dash agreeing on the ambient temp. I get IAT from the bank 1 MAF via OBD.

I would expect IAT to be above ambient when the car is running but I had let the car cool overnight. I'm assuming everything had time to equalize over the 9-10 hours* that it sat there. I could be wrong.

The "clock" sensor is mounted in front of the radiator, just a little off-center to the right.

I'm not an expert on engine control by any means, but, from what I've read, the MAF uses IAT to compute MAF and the ECU uses IAT to adjust how much fuel is injected. I wouldn't be surprised to find out that IAT is involved in valve and ignition timing calcs. How much of an effect IAT has, I don't know. Which is the reason for the original question. I suspect the answer is "Not enough to matter in your DD" but would like to get some advice from someone that knows more than I do.

Edit:
*I didn't pay attention to the time. It was probably closer to 12-14 hours.

i'm just throwing stuff out there.

but what was the actual temperate? i can compare my two temps for you

How sure are you on this? I wanna move that thing and the bar it's mounted too but if its a air bag thing I don't want to touch it!



I think you're over thinking this. First off the car was designed to work so if it was an issue the car wouldn't have been released. Also, that time is probably not long enough. The engine can stay warm a very long time. And the block will "breath" while shut off into the manifold and intake tubes etc. that rubber is basically insulation and the filter can act as a blanket. Check again after 24 hrs and not in a garage, I'd like to see. Also, if the sensors weren't mounted in the intake tube like the MAF is, than it's not apples to apples really. Last the IAT doesn't change AFR. At certain temp points the ecu will pull timing to prevent knock, not fuel.

I'm very sure. Check the FSM to verify (or hold your fingers on the sensing tip and see if the reading goes up). On my '09, it's mounted to a vertical bar that is dead center on the car. Sensor is on right (your left when looking through the grille) side of bar.

I'm not all that worried about it; mainly just curious as to why there is so much difference. The car seems to be running fine. I am a bit concerned about possible long-term damage, but, not freaking out about it.

I'll try letting it cool down longer and see what happens. It will have to be done in the garage - lots of pine trees in my yard and the neighbor's and I don't want sap on my car. :) I have some small fans that I can use to help air circulation in the engine compartment.

Ah. Thanks for that bit of info.



Thanks for the input. I'll try letting it cool down longer tonight (I have some errands to run today).

I'm not sure what you mean by "actual" temp. Ambient temp was 61. I did not have a temp probe in the intake duct. I have a digital thermometer with a wired remote sensor; I'll see if I can feed the probe up into the intake duct and get a reading at the MAF.

As per comment above, I'll be trying again, letting it cool off longer and with some air circulation in the engine compartment. I'll see if I can't get a temp reading at the MAF then. I may just pull the bank 1 MAF out of the intake duct.

you're correct in that the ambient air sensor is mounted in front of the radiator, but what you're not accounting for is that the IAT temperature is taken at the MAF sensor. thats the sensor in your intake tubing just before the throttle body. it is completely normal for the temperature to be higher than the ambient air because the air needs to travel from the intake hole by the radiator all the way up the tubes and measured.

when your car is running, the temperature difference will be significantly higher as there will be some heat soak from your engine

I understand that the IAT comes from the MAF (located in the filter box outlet) and that, when the engine is running, the air will get heated. When my engine is running the difference between ambient and IAT is at least 9-10F; higher when stopped or moving slow. I am seeing the 6F difference when the engine is cold. Or at least I think it was cold - I will be running another, longer test with fans tonight.

Edit: mentioning that the temp sensor is in the filter box made me realize that it is very easy to get the temp in the duct at the MAF when the engine is not running. I just pulled the filter out and stuck a temp probe next to the MAF. The engine is still quite warm and I have to go out of town this PM. I'll report back later this evening.

After letting the car sit overnight, the ambient temp and temp inside duct was 63. Pulled the thermo from the duct and put everything back together. Dash thermo reading 63. Start car and water temp was 63. IAT was 69.

IAT is out of calibration.