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Rewiring a MAP/IAT sensor
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Old 08-20-2019, 04:06 PM   #1
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Default Rewiring a MAP/IAT sensor

I have an 01 RS. It is map based with the IAT and MAP in the same sensor that is bolted to the intake manifold. I’m tired of heat soak and showing 140-150 intake temps when I know the air coming in is much cooler than that. Is there a way to wire in a separate IAT sensor that I can install in the inlet tube so I can get an actual intake temp reading?
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Old 08-21-2019, 04:59 PM   #2
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Huh! Well, that's an interesting question and I don't have a straightforward answer for you. But I do have some thoughts:

The BE/BH Legacy is a MAP setup with a standalone IAT sensor in the plastic "grunt box" right ahead of (from the perspective of air going into the engine ) the throttle body. It should be easy to get a hold of that sensor ( AIR CLEANER & ELEMENT. AIR CLEANER '00MY-'03MY.. For 2001 Subaru Legacy 2.5L MT 4WD L Wagon | Subaru Parts Online )

The next step is to figure out whether:
1) its connector is the same
2) its electrically compatible
3) and it has the same calibration
(1) isn't a deal breaker, just cut n splice as needed. (2) is pretty likely (same era and temp sensor tech doesn't change that often), but (3) is where you're going to run into pain if it's wrong.

So, the real trick is verifying that calibration. You have a couple options there:
- You can either research by part number, maybe try and find the OEM for the sensor and see if you can get a calibration from them.
- You can take a look at the manual for both cars and check the troubleshooting section for the temp sensor and see if you can work out the calibration based on that info
- Or, and this might be easiest: Pick up a sensor from a junkyard and just bench test it. Temp sensors work by changing resistance at different temperatures, so you should be able to test with a multimeter without even applying power. Grab your current one and the new one and test both in the fridge, at room temp and over your toaster

Uhm, if I misspoke anywhere, someone should let me know, but I think that's at least mostly accurate. If you do end up doing this I'll be super curious how much the difference is in temperature. Good luck!
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Old 08-28-2019, 05:51 AM   #3
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Default Intake spacers

I have the G10 intake spacers they are great, other folks also run the throttle body spacer. I see intake temps of ~130', I can palm the runners at full temp.
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Old 09-10-2019, 01:49 AM   #4
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I personally think that intake spacers are not worth it. Lots of trouble for nothing. I have 10mm phenolic spacers and they gave me nothing except for troubles of clearance with the hood and double gaskets... On the other side it gave more room under the manifold, and in my setup with custom fuel lines and hoses it probably helped, I never tried to fit it all without spacers...
But anyways, in terms of heat management - not worth much. Once you get good flow of air - it spends in manifold so little time that difference is negligible. And in light loads high IAT in fact helps you to get better fuel economy
I have logs of IAT mounted on top of the manifold right opposite throttle body and what made huge difference to my IAT readings is intercooler ducting.. If your cooler is not stock - make sure it's ducted properly. Before ducting my IAT climbed to over 60 deg C (140F) quite quickly in 3rd gear pull even on 0.8 bar boost, now IAT is climbing only when car is in vacuum, one airflow is there IAT drops very fast.
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