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Old 04-30-2012, 09:02 PM   #1
expo9091
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Default Cobb sd iat hookup

Hey guys I'm just wondering how to hook up an aem iat sensor to use speed density with.

I read some threads and found I can just wire it to the maf sensor but wanted to make sure I do it right before cutting wires.

Do I completely cut the wires off the maf and run the wires directly from the ecu to the iat? Or do I splice into them while leaving them connected to the maf ( which I am going to assume will give the ecu messed up readings) ?

Also does anyone know if I have to even leave my maf plugged in? Or can I just take it out all together? This is a base map sent by my tuner btw.

Thanks for the help!
Matt
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Old 05-01-2012, 10:36 AM   #2
Cobb Tuning
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Quote:
Originally Posted by expo9091 View Post
Hey guys I'm just wondering how to hook up an aem iat sensor to use speed density with.

I read some threads and found I can just wire it to the maf sensor but wanted to make sure I do it right before cutting wires.

Do I completely cut the wires off the maf and run the wires directly from the ecu to the iat? Or do I splice into them while leaving them connected to the maf ( which I am going to assume will give the ecu messed up readings) ?

Also does anyone know if I have to even leave my maf plugged in? Or can I just take it out all together? This is a base map sent by my tuner btw.

Thanks for the help!
Matt
Hi Matt. Our speed density tuning guide has wiring instructions for aftermarket IAT (in the appendix):
http://accessecu.com/support/docs/tu...sity_Guide.pdf

The IAT sensor is part of the MAF housing, so you can just splice the two wires for the IAT and leave the MAF still functional (if you feel you may need it in the future). Where you splice them is up to you.

You can also entirely remove the MAF housing from the car, just that your tuner would need to disable the three DTCs (P0101, P0102, P0103) in your map and you would need to reflash that map to the car.

Make sure your tuner understands that you are using an aftermarket IAT sensor. It will require a different calibration that the stock one (also described in the guide for GM/AEM sensor).

Bill
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Old 05-01-2012, 05:22 PM   #3
expo9091
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Quote:
Originally Posted by Cobb Tuning
Hi Matt. Our speed density tuning guide has wiring instructions for aftermarket IAT (in the appendix):
http://accessecu.com/support/docs/tu...sity_Guide.pdf

The IAT sensor is part of the MAF housing, so you can just splice the two wires for the IAT and leave the MAF still functional (if you feel you may need it in the future). Where you splice them is up to you.

You can also entirely remove the MAF housing from the car, just that your tuner would need to disable the three DTCs (P0101, P0102, P0103) in your map and you would need to reflash that map to the car.

Make sure your tuner understands that you are using an aftermarket IAT sensor. It will require a different calibration that the stock one (also described in the guide for GM/AEM sensor).

Bill
Thanks for the fast reply. I actually looked through that first and I missed it! Haha. My tuner actually has me putting the aem sensor on : ) Thanks again for all the help and the fast reply.
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Old 01-25-2013, 12:10 PM   #4
matts
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I used the iat calibration values in the sd pdf from cobb. I found the sensor to be off like 20 degrees . Should those values be corrected to read the proper temp?


Im using an AEM unit

Last edited by matts; 01-25-2013 at 12:11 PM. Reason: sensor info added
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Old 01-25-2013, 02:07 PM   #5
Cobb Tuning
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Quote:
Originally Posted by matts View Post
I used the iat calibration values in the sd pdf from cobb. I found the sensor to be off like 20 degrees . Should those values be corrected to read the proper temp?


Im using an AEM unit
What are you comparing the reading to? And in what direction is it off? What testing conditions (engine hot, engine cold, etc.)?

Bill
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Old 01-25-2013, 02:27 PM   #6
matts
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When I hooked the sensor up for the first time, with a ice cold car (literally it was 20 degrees). I flashed the map with cobb aem calibration #s. and turned on the ignition. The intake temp said 42.

I decided to drive the car for a bit to see if anything changed. When I idled the car it would rise, as it should (heat soak). Then while driving, it would go back down to the 42 deg reading and hold pretty steady. My outside temp in the car said 20.
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Old 01-26-2013, 10:17 AM   #7
Cobb Tuning
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Quote:
Originally Posted by matts View Post
When I hooked the sensor up for the first time, with a ice cold car (literally it was 20 degrees). I flashed the map with cobb aem calibration #s. and turned on the ignition. The intake temp said 42.

I decided to drive the car for a bit to see if anything changed. When I idled the car it would rise, as it should (heat soak). Then while driving, it would go back down to the 42 deg reading and hold pretty steady. My outside temp in the car said 20.
Can you attach your map to a post over at cobbforums.com (Select "Go Advanced" and "Manage Attachments" when posting)?

Bill
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Old 01-27-2013, 12:22 PM   #8
Cobb Tuning
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Quote:
Originally Posted by matts View Post
When I hooked the sensor up for the first time, with a ice cold car (literally it was 20 degrees). I flashed the map with cobb aem calibration #s. and turned on the ignition. The intake temp said 42.

I decided to drive the car for a bit to see if anything changed. When I idled the car it would rise, as it should (heat soak). Then while driving, it would go back down to the 42 deg reading and hold pretty steady. My outside temp in the car said 20.
Ok - looked at your map and the IAT calibration is good. Make sure that you reflashed that map to your car (and not real-time flashed). A reflash is the only way that particular table will be changed in the ECU.

The outside temperature reading is not really an accurate means of determining whether your IAT reading is off or not. The engine will retain at least some heat for a very long period of time which can effect the sensor reading relative to an outside temperature reading. Also, the sensor being in
the intake piping is somewhat insulated from outside air. There may be other reasons, but from what I've seen, even on stock cars with stock sensor, IAT always reads higher than outside temperature, even on cars that have been sitting for quite a while.

If you still have a MAF sensor installed (and it is calibrated properly), a better way to verify the IAT reading is to look at the estimated VE monitor. If the IAT reading is too high, the estimated VE will be higher than expected. If you tune in SD mode and use the estimated VE that is higher than expected, you will run too rich. This is an indirect way to determine whether the given IAT reading is accurate or not. Of course, if your IAT sensor is heatsoaked (due to extended idling/etc), it will also have the same effect, so not necessarily just because the IAT calibration is off. We have used the AEM calibration given in the guide in a number of cars without issue, so unless AEM changed something with their sensor, the IAT calibration given should be accurate.

Bill
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Old 01-28-2013, 12:29 PM   #9
matts
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AEM website states this "Due to the self-heating effects of the thermistor the resistance is dependent upon the application."

This being said, I will assume it is normal for it to read a bit different than the theoretical calibration numbers.

IMO If my car sits for a day in the cold (without being started), the sensor should read the exact temp as the air.

Maybe 20 degrees error is trivial at the lower temps, I will monitor the error as the weather changes (and ambient temps get warmer).

In the meantime, I am going to adjust the calibration numbers to read the correct temp.
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Old 01-28-2013, 12:50 PM   #10
Cobb Tuning
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Quote:
Originally Posted by matts View Post
AEM website states this "Due to the self-heating effects of the thermistor the resistance is dependent upon the application."

This being said, I will assume it is normal for it to read a bit different than the theoretical calibration numbers.

IMO If my car sits for a day in the cold (without being started), the sensor should read the exact temp as the air.

Maybe 20 degrees error is trivial at the lower temps, I will monitor the error as the weather changes (and ambient temps get warmer).

In the meantime, I am going to adjust the calibration numbers to read the correct temp.
The resistance varies based on the application, but this is dependent on the ECU, which will be the same across all of these Subaru applications. We've done the theoretical math and tested the sensor with an ECU bench set-up with the calibration that we ultimately came up with in the guide to verify it reads the same as the temperature reading of the room. A sensor mounted in the somewhat isolated/insulated environment in the intake tract is not the same as a reading in free air. There's the potential for the sensor to retain some level heat above outside air in that case, especially with only a day since the engine was up to operating temp. If possible, you could remove the IAT sensor and place away from engine bay (as much as possible) and let the car sit for a longer period of time (with hood up) and see what its reading is. Would be curious to see what that shows.

Bill
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Old 01-28-2013, 01:02 PM   #11
matts
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I can check it out when the IC comes off next time. I will post the results and include another reference of ambient temp.
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Old 02-09-2014, 01:23 AM   #12
maxpowr
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Bump.

Phatron
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