Relocating the IAT sensor

[natenkiki2004]

Has anyone done this? I'm talking about the air temp sensor sitting near the vacuum tree on the upper intake plenum. On newer Explorers, the upper intake is plastic and it seems on many other newer vehicles, the IAT is located at/in/near the MAF. Even Ford went and put the IAT in the MAF sensor (6-wire MAF).

I'm just curious if anyone has done this mod, either on an Explorer or other vehicle. I couldn't find anything in the way of a intake spacer to help keep the plenum cooler. So I'm wondering if maybe the computer got the temp of the air from the plastic tube or air filter box, if maybe the temp reading would be more accurate. The upper intake plenum is a large and sealed chamber with thick aluminum. It might heat the air up quite a bit especially with short stops.

There shouldn't be any huge difference while driving though, the air should travel through fast enough.

I don't know... let's have a discussion about it

 

[2000StreetRod]

spark advance

I don't know about your 1st Gen but on my 2nd Gen the PCM can reduce spark advance based on IAT so if max performance is desired then an accurate IAT is important. I think the closer the sensor is to the lower intake manifold the more accurate the temperature. To avoid detonation you want the sensor measuring the warmest airflow. The stock tune assumes a stock location for the sensor. Changing the sensor location could invalidate the calibration constants that I assume are based on factory testing. However, unless forced induction is being added (which significantly increases IAT downstream of the compressor) I suspect moving the sensor will have minimal impact.

When I upgraded my 6 wire 55 mm MAF (integrated MAF/IAT sensors) the Lightning 90 mm MAF sensor had no IAT sensor so I installed one in the main intake hose between the MAF sensor and throttle body. I didn't notice any change in my IATs.

 

[natenkiki2004]

I figured it would affect spark and fuel trim. I do agree that it's best to measure the air as closest to the combustion chamber as possible. That's where it will end up after all.

I guess my thought/question is...
Isn't the upper intake on the 2nd gens plastic? Being that the ones on the 1st gen are thick chunks of aluminum, they wick heat really well. I'm wondering if the sensor itself is getting artificially high temperatures, particularly on warm starts and until enough air flows in to cool the intake and the sensor so it reads properly.

One way to test this would be to hook an ohm meter up and actively measure it while driving, parked, idling and other varying conditions to see if there's certain spikes that can be avoided by possibly relocating the sensor to a plastic housing, away from the engine.

BUT... maybe the Ford engineers figured all this out. Or maybe the 1st gen was a huge learning curve and that's why so many things changed for the 2nd gens.

 

[2000StreetRod]

injection molding vs casting

I suspect Ford's main objective in switching from metal to plastic is cost and possibly weight. Not only is plastic less expensive than metal but the injection molding of plastic is probably simpler and quicker than casting metal.

I doubt you'll be able to monitor the resistance of the IAT while driving without disconnecting it from the PCM. I think the PCM applies a known voltage to the sensor which is probably different from your meter's applied voltage when measuring resistance. You'll probably have to measure the voltage drop across the sensor and compare that to a table for the sensor characteristics. It was a lot easier for me with OBD-II. I just datalogged the value from the port that the PCM had converted to degrees.

As I recall the IAT sensor element is insulated from it's housing. That should reduce the conduction of heat from a metal plenum.