GM AIT Sensor Install

[Doppelganger]

If you run a TMIC you install a GM IAT Sensor in the TMIC near the Throttle Body.

If you run a FMIC you install the GM IAT Sensor post Intercooler near the throttle body preferably in a straighter part of the piping.

Once the GM IAT is installed you clip the IAT wires from the MAF and then run the GM IAT wires to the MAF Wiring Harness.

You will then have to tune your ecu for the different IAT Sensor but once installed you will have an accurate Air Intake Temp reading post intercooler and that's what your ECU will be using to make its adjustments due to actuall temps and not the outside air temp that your MAF is reading.

So I was wondering if any of you have done this to your Subaru and what your opinion is on this mod because it's most likely is going to be a mod I do before I retune.

 

[HolyCrapItsFast]

Not really much to say here other than if you are going to speed density then this is required for accurate and consistent results. The way you described it is dead on. This is not the mod you want to do if you are staying MAF though.

If you plan on maintaining the MAF for the purpose of using the MAF/SD blending feature then your best bet would be to maintain the stock AIT sensor in the MAF housing and go with a blow through MAF set up. This will place the sensor after the intercooler and maintain accurate temp data for both MAF and SD. This assumes you have a FMIC though. The only solution for a TMIC is to go full SD and move the sensor as you described

 

[Doppelganger]

I have heard mixed results with blow thru MAF due to oil contamination on the MAF and also heard they are a PITA to tune or keep in tune. This method is the method that my tuner uses (that's if my Version 1 AP was still supported) when I was inquiring about tuning.

I pretty much think it sound like a legit modification to do but was wondering if any of you have had experience with this not to mention I also wanted to share his technique of getting real IAT while still keeping the stock MAF sensor.

 

[HolyCrapItsFast]

Oh yes it is a very legit method but only if you are running full speed density. This method is actually outlined in Cobb's SD tuning guide. Any time you introduce the MAF into the mix, like in a hybrid system, then the temp sensor must be moved to the throttle body to get SD working properly, and then the MAF must be moved to the same location as the temp sensor or somewhere close and in the same line so that MAF can work. As you mention, doing so brings up other concerns but at that point you have to weight the pros and cons. Tuning blow through can be very reliable provided you find a place to mount it that is seeing laminar flow. Often this is not possible because there are few straight runs of pipe prior to the MAF. in these cases I choose to go full SD.

In a full MAF car the real and most accurate place to measure the temperature of the air is at the MAF location. This is why they combine the two sensors in to one (flow and temp). Only in a pure SD application will the most accurate place be at the throttle body. In any MAF application, it is measuring the mass of the air coming in at that point and once that is known and the air is metered, it doesn't matter what happens to its properties after that point because mass is absolute and the molecules have been counted. In speed density it relies on pressure and temp to derive the amount of air entering the motor so it is more critical to get the location of your temp sensor correct.