The purpose of this guide is to assist those running with standard TMIC( Top mount intercooler) that suffer from excessive heat soak from those hot Aussie summer days. The idea and concept of the mod itself was given to me by MSR(Michael South Racing) so all credit goes to good old Mike. He's a wealth of untapped subaru goodness.
This guide is not a solution for the problem, however it will aid to reduce the unnecessary damage due to engine knock. Although the difficulty of this modification is not too high you can cause damage to your engine if done wrong. If in doubt, get your mechanic to do it for you.
The mod will bring your intake air temp sensor closer to the intake manifold and give you true IAT(Intake air temperature) readings. This will tell your ECU(engine control unit) the true temp and will assist in the corrections before the engine even has a change to knock your ECU will have already corrected the timing.
However doing this mod WILL REQUIRE A RETUNE, you will be removing the standard IAT sensor replacing it with an aftermarket one and then moving it to a different location on the air system. This WILL cause problems if you run it on your standard tune. You will need to tell your ECU what the new optimal operating temperature is as the sensor has been moved and the actual running temperature will have changed. The old optimal will no longer be valid.
For example my IAT went from ~40 running temp to only ~15 post inter cooler. This difference in reading was the result of my CAI(cold air intake) with engine bay heat soak.
Skill level with a soldering Iron : 6/10
Skill reading electrical diagrams : 7/10
Parts needed:
A good soldering Iron;
60% tin 40% lead solder - the cheap supercheap stuff will not do;
Alot of electrical tape;
wire conduit;
side or wire cutters;
Spare IAT sensor;
New harness for spare IAT sensor;
~80cm decent trailer tinned copper wire 2 green and black preferred;
Drill;
Cable ties;
Tap and die;
Pre installed PCV catch can;
Loctite sealer;
Wire crimper;
oBD2 diagnostic tool;
Shrink tubing;
4 can's of carby cleaner - depending on how large your TMIC is; and
Air compressor with air blower.
First step is to remove the standard B4 TMIC. The guide for this has been done so I will not redo it.
Second step is to measure a point to install your new intake sensor on the TMIC. Be sure to test place it and ensure it doesn't get in the way of turbo vac lines or throttle cables.
Drill and tap the optimal point. I put mine ~ 5cm from my intake manifold join point. I was not confident in this so I had my mechanic drill and tap the hole. ( while he was doing this I fixed his dyno since it broke )
After the hole is drilled, carby clean the whole TMIC interior and blow it with air from the air compressor. Ensure all metal shavings and oil is removed. You will need to repeat this until the entire TMIC is sparkly clean. Oil will cause faulty readings on the IAT sensor, ensure there is no remaining residue in the TMIC.
Loctite the IAT sensor threads and attached the IAT sensor into the TMIC, be careful to ensure you don't over tighten the IAT sensor and hit the inside of the TMIC fins. A few washer may be required to give some clearance. Mine did not require this, as seen in Figure 1.
20140615_145813.jpg 121.34KB
15 downloads
Figure 1.
Remove the wire loom from the MAF(Mass air flow) sensor and peel back the tape and conduit. It will look something like Figure 2.
20140615_150302.jpg 110.18KB
14 downloads
Figure 2.
Cut IAT sensor signal wire 4 on the attached Reference (IAT.pdf). Solder this to a new green wire to go to the IAT sensor harness.
Splice the GND wire 2 on the attached Reference (IAT.pdf) to an additional black wire. Do not directly cut this wire as it is still required by the MAF sensor to function.
I used wire connections as can be seen in Figure 2.
The end result you will have the harness looking like Figure 3 and 4.
20140615_151254.jpg 168.1KB
14 downloads
Figure 3.
20140615_151234.jpg 102.79KB
11 downloads
Figure 4.
Test run and then finally cable tie the new IAT sensor harness. It should look similar to Figure 5.
20140615_151918.jpg 161.04KB
12 downloads
Figure 5.
Done turn on the car and test. Then unplug IAT sensor harness and test again engine light should come on.
Clear engine light and plug IAT sensor harness back in. Engine light should remain off.
Reference Material
IAT.pdf 29.02KB
6 downloads
IAT.pdf
Related Material
MAF.pdf 30.53KB
2 downloads MAF sensor pin numbes
Pin table.pdf 24.46KB
2 downloads ECU pinouts.
20140615_152307.jpg 50.69KB
10 downloads
IAT Sensor part number
20140615_152247.jpg 113.17KB
11 downloads
IAT sensor harness
