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Old 03-01-2013, 06:24 PM   #1
poly_poly-man
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Default My engine keeps eating my custom IAT

So, in changing to speed density, I wanted an IAT sensor in the manifold, for obvious reasons. I was turned on to the method of replacing the PCV valve with an IAT sensor by putting the thermistor through the plug and siliconing it in. This works fairly well.

Unfortunately, it doesn't always. First, I did this with the thermistor cut out of my MAF sensor. Worked fine for a while, but at some point the head of the sensor exploded - the little bulb was broken in half. I replaced it with an omega sensor (44004), and that worked fine for a while - at one point the boost shot the sensor out of the plug, but I just re-sealed it in with more silicone. More recently, though, the sensor exploded again - I have both the leads still attached to the wiring, but no sensor head whatsoever.

I realize that the conditions in the manifold aren't great - relatively high pressure (and vacuum), temperature, oil from the PCV, etc. However, I don't see why my sensors keep exploding - other people with manifold IAT sensors don't seem to have nearly as many issues as I do.

I'm going to buy another omega sensor, but what can I do to keep it from destroying itself again?
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Old 03-01-2013, 06:59 PM   #2
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I don't know what a "performance" IAT sensor looks like other than the thermistor in the MAF, but considering we're measuring temperature and not flow rate or a derived voltage of some sort, couldn't you shield the thermistor from the direction of flow? Or sheath it in a tube?
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Old 03-01-2013, 09:07 PM   #3
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02 wrx IAT is taken from maf sensor. and if you "made" it work with
just the bulb..good for you. but now it keeps failing. its time to get a real
IAT sensor and wire it correctly.
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Old 03-02-2013, 12:21 PM   #4
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the problem with shielding it is that I want to make sure the temperatures keep up - I tried to wrap it in electrical tape last time, but no dice. Maybe I'll try heat shrink this time...

By a "real" IAT sensor, are you talking like a GM sensor? The omega sensor is literally what the GM guys upgrade to...
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Old 03-02-2013, 07:56 PM   #5
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For one, no silicone, unless it's high temp rtv. But I wouldn't even do that, does the sensor's thread pitch not match up to the PCV threads in the manifold? Tapping a new, larger, hole in the manifold and inserting an adapter would be the way to go. The only other thing I might do is relocate the sensor to a less volatile location and retune. A lot of work, but I guess you would have to weigh that against how often you are fixing this recurring problem.


~Josh~
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Old 03-02-2013, 10:14 PM   #6
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If u got a fmic mount it on the pipe with a bung
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Old 03-03-2013, 01:21 AM   #7
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Quote:
Originally Posted by gtasti View Post
If u got a fmic mount it on the pipe with a bung

the outlet side endtank would be better
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Old 03-03-2013, 03:29 AM   #8
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Quote:
Originally Posted by ballitch View Post
For one, no silicone, unless it's high temp rtv. But I wouldn't even do that, does the sensor's thread pitch not match up to the PCV threads in the manifold?
I think you misunderstand the situation - first off, yes it's high temp rtv, as was recommended when I first did this. What I did was actually cut the back, including the valve part, off the PCV valve, so all that's left is a plug with a hole in it. I order the omega thermistor, and it is literally just that, the thermistor bulb with two leads. I solder that to a connector that I repurposed from the DRL resistor, wrap it up in electrical tape, shove it in the hole, and seal the whole mess with silicone. The post from the original thread where I was asking about it. I didn't bother to find a new plug with the right thread pitch, so it looks just slightly different than that.

As for the FMIC discussion, I'm still on the TMIC, and from what I've heard, anywhere pre-TB is a terrible place for the IAT relative to the manifold. It makes sense, too.
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Old 03-03-2013, 12:56 PM   #9
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Quote:
Originally Posted by poly_poly-man View Post
As for the FMIC discussion, I'm still on the TMIC, and from what I've heard, anywhere pre-TB is a terrible place for the IAT relative to the manifold. It makes sense, too.
That depends on your tuner, your EM, and what the tuner and map is designed for.

You'll see lots of 500+ whp subarus running around with the IAT shoved into the fenderwell in free air and running perfectly fine in all conditions.

You'll also see a lot of 300+ whp subarus on SD using the factory MAF sensor for the IAT.

What you won't see... Is a lot of subarus running IAT on the intake manifold because heat soak is bad for business. At idle, your IATs will skyrocket on the sensor because it's soaking - this is even worse with a TMIC.

What you'll also have a hard time finding... is correct temp. compensation maps for your IAT location. Which means you need to build your own, which takes a lot of time, testing, and patience.

Every few months you'll see huge multi-page threads arguing IAT locations until people are blue in the face. The fascinating part is... The higher HP the car, the less people seem to care about where the IAT sensor goes.
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Old 03-03-2013, 01:14 PM   #10
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^Honestly, the discussion for me at this point is that the original location was REALLY bad (yeah, maybe I could've tuned around it, but that makes a lot of assumptions about turbo and intercooler efficiency, and wouldn't make things easier for certain), and this required no extra drilling or tapping. Besides, I believe the base carberry tune is based on the group n car having the spec c IAT tapped into the manifold anyway, so those compensations are designed for more or less the location I have it. Temperature compensation has not been my issue with tuning since I've moved the IAT to where it is now. Besides, with the sensor insulated from the plug itself, it doesn't heat soak much more than the manifold air itself does anyway, which is important to factor in anyway. In any case, I have the MAW/TiC composite TGV deletes on my car, which keep the manifold pretty damn cold relatively.

So yeah, does the location matter that much? no. So, why not put it where it is right now?

And, in case it wasn't clear, I'm my tuner, my EM is the stock ECU running carberry speed density, and except for these hiccups, the tuning is not coming along badly.
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Old 03-03-2013, 08:11 PM   #11
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Quote:
Originally Posted by poly_poly-man View Post
^Honestly, the discussion for me at this point is that the original location was REALLY bad (yeah, maybe I could've tuned around it, but that makes a lot of assumptions about turbo and intercooler efficiency, and wouldn't make things easier for certain), and this required no extra drilling or tapping. Besides, I believe the base carberry tune is based on the group n car having the spec c IAT tapped into the manifold anyway, so those compensations are designed for more or less the location I have it. Temperature compensation has not been my issue with tuning since I've moved the IAT to where it is now. Besides, with the sensor insulated from the plug itself, it doesn't heat soak much more than the manifold air itself does anyway, which is important to factor in anyway. In any case, I have the MAW/TiC composite TGV deletes on my car, which keep the manifold pretty damn cold relatively.

So yeah, does the location matter that much? no. So, why not put it where it is right now?

And, in case it wasn't clear, I'm my tuner, my EM is the stock ECU running carberry speed density, and except for these hiccups, the tuning is not coming along badly.
maybe you need to fire your tuner and get somebody who knows what they are doing
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Old 03-03-2013, 11:29 PM   #12
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The outlet side of the IC is going to be alot better than the intake manifold since the sensor will just heat soak and not get accurate readings. And please stop doing it the ghetto way and use the Camaro IAT sensor.
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Old 03-03-2013, 11:37 PM   #13
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Quote:
Originally Posted by RemlapaN View Post
That depends on your tuner, your EM, and what the tuner and map is designed for.

You'll see lots of 500+ whp subarus running around with the IAT shoved into the fenderwell in free air and running perfectly fine in all conditions.

You'll also see a lot of 300+ whp subarus on SD using the factory MAF sensor for the IAT.

What you won't see... Is a lot of subarus running IAT on the intake manifold because heat soak is bad for business. At idle, your IATs will skyrocket on the sensor because it's soaking - this is even worse with a TMIC.

What you'll also have a hard time finding... is correct temp. compensation maps for your IAT location. Which means you need to build your own, which takes a lot of time, testing, and patience.

Every few months you'll see huge multi-page threads arguing IAT locations until people are blue in the face. The fascinating part is... The higher HP the car, the less people seem to care about where the IAT sensor goes.

90% of this is false information....




@poly_poly-man - I have heard of one other guy having an IAT sensor get blown apart in the intake manifold. I think it may be "backfiring" back into the intake manifold that causes it, so try to think of reasons why that would happen. Possibly cam timing or valve issues, running too rich, ignition timing related? Are you running anti-lag or rotational idle when it happens?
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Old 03-04-2013, 10:50 AM   #14
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Quote:
Originally Posted by Carbibbles View Post
@poly_poly-man - I have heard of one other guy having an IAT sensor get blown apart in the intake manifold. I think it may be "backfiring" back into the intake manifold that causes it, so try to think of reasons why that would happen. Possibly cam timing or valve issues, running too rich, ignition timing related? Are you running anti-lag or rotational idle when it happens?
I'm 95% sure my valves are good - I have no AVCS, the timing belt is in good shape, and I haven't noticed any issues. Anti-lag and rotational idle are off, but I have been using the launch control (fuel cut) a bit, and I am just getting around to leaning my map out to saner values. I'm not sure the exact moment the sensor fails, but I'm pretty sure it's related to the launch control.

I'll try to avoid using the launch control at least until the rest of my tune is a bit more solid, I did not realize that that could cause issues in my intake manifold.
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Old 03-04-2013, 08:40 PM   #15
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...............
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