tapping egt in downpipe - Subaru WRX Forum
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post #1 of 16 Old 03-31-2012, 05:06 AM Thread Starter
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tapping egt in downpipe

quick question. is it possible to tap an aftermarket downpipe and relocating the egt probe from the uppipe to the downpipe?
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post #2 of 16 Old 03-31-2012, 12:49 PM
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Possible, yes. Should you, no.
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post #3 of 16 Old 03-31-2012, 02:00 PM
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When I ordered my GrimmSpeed ported/polished/ceramic coated stock exhaust manifold, I also had them tap a hole for my Prosport EGT sensor in this location (driver's side)
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post #4 of 16 Old 03-31-2012, 08:51 PM Thread Starter
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oh ok. if i wasnt broke i would send mine to grimmspeed and have them do the same. thanks for the info guys
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post #5 of 16 Old 03-31-2012, 10:07 PM
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Two completely different EGT sensors though. Manshow is talking about an aftermarket one that is much smaller. If you relocate the the oem sensor to the DP and you have an OEM up pipe, you're just ignoring a problem. If you have an aftermarket up pipe, and you are trying to get the check engine light to shut off, just do the resistor mod and remove the sensor alltogether.

BTW Manshow, you'll be hearing from my lawyer. That is a copyrighted image property of me

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post #6 of 16 Old 03-31-2012, 10:31 PM
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The price for the GrimmSpeed stuff is fairly reasonable... you can send your stock exhaust manifold back to them and get a core refund of $140. Having the EGT probe several inches from the block gives a much more accurate temperature reading than having it in the downpipe if you're reading it on a gauge.

Since you're swapping up pipes, yeah, the resistor mod is definitely the way to go.

Good call Chris - I didn't realize they were different sizes. I hope you don't mind the tiny little red arrow I added on your pretty picture.

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post #7 of 16 Old 04-01-2012, 12:34 AM Thread Starter
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actually i am switching uppipes and doing the resistor fix until i figure out what im going to do with the egt
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post #8 of 16 Old 04-01-2012, 12:39 AM
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My car hasn't had an EGT sensor in the up-pipe since 2003.
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post #9 of 16 Old 04-01-2012, 01:09 AM Thread Starter
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how r u checking ## exhaust temps then?
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post #10 of 16 Old 04-01-2012, 09:45 AM
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The resistor tricks your car into thinking the temps are ok. When you do that mod, you don't need the sensor in the up pipe at all unless you're in an extreme racing situation and you want to know when things are going to melt. Honestly, my Prosport EGT gauge is mostly for show. I have the alert set for just under the historically stored maximum reading, so if the temperature creeps up that high again, the gauge face will flash red and it will beep (I currently have it muted) and I'll back off the throttle, but other than that, I rarely look at it.

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post #11 of 16 Old 04-01-2012, 10:40 AM
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Quote:
Originally Posted by Klone View Post
how r u checking ## exhaust temps then?
You don't understand why that EGT is even there. The ONLY reason it is there is because the OEM up pipe has a cat in it. That egt sensor is there to tell you if the exhaust gasses are too hot for the cat to handle, causing it to fail/go through turbo/etc. Once you pull the oem up pipe out and put in a catless one, you don't need it anymore. FYI, all the STI's and 2006 and later WRX's have no cat in the up pipe, and also don't have an EGT sensor anywhere on the car. They come that way from the factory now.

The OEM sensor cannot tell you what your EGT's are anyways, it's basically an on/off switch of too hot/not too hot. If you want to be able to read what your EGT's are then you need to install an aftermarket EGT sensor with a gauge wired up in the cabin for that. The downpipe is about the worst spot to put it anyways. You want to mount the sensor within about 3" of the head, so somewhere on the exhaust manifold. If you mount it in the downpipe you're seeing EGT's that are about six feet old and a couple hundred degrees less than what they actually are.

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post #12 of 16 Old 04-01-2012, 04:29 PM
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^ Excellent explanation

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post #13 of 16 Old 04-01-2012, 07:58 PM Thread Starter
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Quote:
Originally Posted by RcrsWetDream View Post
You don't understand why that EGT is even there. The ONLY reason it is there is because the OEM up pipe has a cat in it. That egt sensor is there to tell you if the exhaust gasses are too hot for the cat to handle, causing it to fail/go through turbo/etc. Once you pull the oem up pipe out and put in a catless one, you don't need it anymore. FYI, all the STI's and 2006 and later WRX's have no cat in the up pipe, and also don't have an EGT sensor anywhere on the car. They come that way from the factory now.

The OEM sensor cannot tell you what your EGT's are anyways, it's basically an on/off switch of too hot/not too hot. If you want to be able to read what your EGT's are then you need to install an aftermarket EGT sensor with a gauge wired up in the cabin for that. The downpipe is about the worst spot to put it anyways. You want to mount the sensor within about 3" of the head, so somewhere on the exhaust manifold. If you mount it in the downpipe you're seeing EGT's that are about six feet old and a couple hundred degrees less than what they actually are.
aaah who said i didnt know why the egt is in the stock uppipe? i know the later wrx/ sti dont have them. the reason i was asking about the egt in the first place is because my cobb accessport reads it and i still wanted to be able to keep an eye on it after i removed the stock uppipe.
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post #14 of 16 Old 04-01-2012, 08:20 PM
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Quote:
Originally Posted by Klone View Post
aaah who said i didnt know why the egt is in the stock uppipe? i know the later wrx/ sti dont have them. the reason i was asking about the egt in the first place is because my cobb accessport reads it and i still wanted to be able to keep an eye on it after i removed the stock uppipe.
The stock EGT gauge is pointless. Even more pointless is putting it in the downpipe. Do you even know what the numbers mean? If you did you would not be wanting to take the reading from the downpipe. It's like trying to figure out what the temperature is in your house by reading the thermometer outside.

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post #15 of 16 Old 04-01-2012, 09:29 PM Thread Starter
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Quote:
Originally Posted by dumdum View Post
The stock EGT gauge is pointless. Even more pointless is putting it in the downpipe. Do you even know what the numbers mean? If you did you would not be wanting to take the reading from the downpipe. It's like trying to figure out what the temperature is in your house by reading the thermometer outside.
Noooo i dont.... haha well i get what ## saying
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