Typically IAT temperaures run several degress higher than what the incoming air really is. Does the ecu internally compensate for this ? Because if not then the ecu is working off wrong information, isn't it ?
Why wouldn't they install the IAT sensor somewhere further upstream and as far away as possible from the effect of engine heat ?

 

It is giving the most accurate reading possible. Right before the air enters the combustion chamber. Some people relocate it to infront of the TB.

It was designed that way, so it works like it is suppose to.

 

I think it's undercompensating for ambient air temperatures that differentiate too much from the IAT sensor's immediate reading because it takes too much time for the sensor to make up the delta between the two temperatures, and in extreme cases, it may never be close enough to provide an accurate correction factor.

That's just what I think. No hard data.

 

You would also have to factor in the wind chill factor too, But, The ECU just matches the reading to it's map. If there was a big difference of 10 degrees or so it might step up or down.

Also the sensor does not compute, it just provides the reading. Now this reading could be off, as in a bad sensor, build-up on the tip, and voltage drop from the sensor to the ECU. and or to ground.

Let's say the ECU did over compensate. What would happen? Add more gas?
Then the O2s would see it and re-compensate for it.

The ECU doesn't cares about ambient air temp's. Just the air temp in the manifold.

 

Well here's a real case -
Outside air temp is 39°F. On a cold start the IAT reads 64°F. Reasonable since it was inside the garage and the temp inside the garage was about 55-60°F.
Now I start the car and ride around for a while so its heated up good. IAT hovers around 70-75°F while driving. Then I stop for about half hour. Come back and see IAT is 96°F. Still reasonable since the air sitting in the IM is heated up by the engine.
At this point I start driving around again but even after several minutes of driving in 39°F outside air temperature the IAT barely drops below 90°F.
I don't believe the 39°F air rushing in gets heated up to 90°F by the time it makes to the IAT!! I find it hard to believe at this point the 'accurate' temperature of the air is really 90°F!
I can only imagine what the temperature must be in summer!

 

Have you tried a replacement and does it still do it?

It seems that it is sticking at 90 degrees is why I ask. I think I payed $15 at the dealer for it. They do also get build-up on them and that might be keeping the temp at 90.

I have seen people that plug off the hole and just let it sit out. Also like I said before you can relocate it to the intake tube before the TB. Like most cars have. Some have it in the air filter box too. But it goes back to the design of the system.

 

That's my exact reasoning for why colder ambient air temperatures produce leaner fuel mixtures and warmer ambient air temperatures produce richer fuel mixtures than what you tuned at.

It's also the same reasoning for why the motor leans out on a warm start for the first couple of minutes after the IAT sensor has heat soaked.

 

well I pulled out the sensor and did some checking. the sensor is fine. and it updates pretty quickly too - I can see a difference right away as I pull the sensor out and then put it back in. My hunch is that its not done right. The metal housing of the sensor in contact with the IM (metal) serves as a great heat transfer path and the sensor remians as hot as the IM surface because of that.

I don't know whether it will make any difference or not but I might move the IAT sensor out of there and somewhere up near the start of the intake tube. That just seems the right place for it to be.
Are there dummy plugs available to plug the original sensor location ? or will I have to buy a new one ?

 

You can block it off with a strip of aluminum or get another sensor. Hit up a junkyard, or get a cheapie from the parts store.

 

Also, think about getting one of Hondata's intake manifold gaskets. It reduces heat soak into the manifold, there-by giving a more accurate reading, and colder air at the same time. I tested this in the winter. It was 12 degrees outside, and I had the stock gasket on there, with a cold air intake (gulping air from the freezing fenderwell. I did a full throttle run, and popped the hood. The intake felt a little cold, but there was quite a bit of heat soak. I installed the gasket, and did a run. I felt the im after that, and it was ice cold. The car felt fast on the butt dyno also. Hondata claims a small gain, probably around 3-5 more hp. And the IAT read lower temp.