EGT Sensor & Placement Questions

Post by **Legacy777** » Sun Sep 13, 2009 3:40 am

I did a little searching here and found a couple threads regarding EGT placement....and there seemed to be some consensus....but I'm still not sure. I've got a set of the JDM headers. I just cleaned them up, and plan to have them coated. So I want to try and figure out what I'm going to do before they get coated.

http://bbs.legacycentral.org/viewtopic. ... egt+sensor

Other question is in regards to the sensor itself. I want to hook it directly into the Link, so I don't really need the gauge. However I will need the calibration curve for the senser, and I haven't run across any yet.

Post by **Legacy777** » Mon Sep 14, 2009 6:10 pm

Here's pics of the manifold.

http://main.experiencetherave.com/subar ... G_0483.JPG

asc_up · Post by **asc_up** » Mon Sep 14, 2009 6:26 pm

I have mine at the bottom of the up-pipe. I did this so I can monitor the EGTs going to the turbo. I'm under the impression that our pistons have some sort of cryo-treatment so they should be able to handle more extreme temperatures. The fins on turbos, however, are not treated, so you want to make sure that the EGTs going to to the turbo do not exceed 1620*F which is the melting point of aluminum.

Just my thought on the matter.

Post by **Legacy777** » Mon Sep 14, 2009 6:43 pm

I had another tuner mention putting it in the up-pipe at the stock location the WRX has its at.

I had thought the WRX has one to monitor cat temperatures primarily.

I guess I need to figure out what I want to monitor. Ideally, the EGT would be for a tuning aid, and monitor to make sure temps aren't getting too hot. But again....temps will vary depending on mounting location.

asc_up · Post by **asc_up** » Mon Sep 14, 2009 7:05 pm

Well if you put it at the base of the up-pipe, you can tune for a maximum of 1620*F EGT, but if you put it any closer to the exhaust ports, then you'll have to either guess at what the EGT is at the turbo or just tune based off of the temp at the sensor, thus not allowing you to tune for maximum power.

93forestpearl · Post by **93forestpearl** » Mon Sep 14, 2009 7:34 pm

I've noticed EGT's can vary wildly dependuing on where you place the sensor. Ideally, I would like to have four sensors placed an inch from the exhaust ports. Many people place the thermocouple near the exhaust port of the problematic cylinder (3 or 4?).

In laminar flow, the EGT's will cool quickly from the port where a couple inches could mean a hundred degrees or more. Turbulence will cause the sensor to read higher, as isaw from my plcement in the collector right before the uppipe, where there is a nice flat spot for tapping. I would see upward of 1700 degrees there under load, yet I never melted anything.

For instance, check out this video of a Honda F1 motor, that most of us have probably seen. Notice how hot the exhaust manifold gets right by the head, and also by the collector. The primaries aren't glowing nearly as much.

http://www.youtube.com/watch?v=rp4SV8FGZoo

Post by **Legacy777** » Mon Sep 14, 2009 9:05 pm

I guess that still kind of leaves me with a decision where to put something...

Post by **Legacy777** » Tue Sep 15, 2009 6:27 pm

I ended up getting this comment back regarding EGT placement:

we place the EGT sensor in the up pipe because it is the most accurate placement for the EGT's when using 1 sensor. If you are using 4 EGT sensors (for individual cylinder trimming) then one in each header tube would be ideal.

asc_up · Post by **asc_up** » Tue Sep 15, 2009 8:06 pm

So now you need to decide how much money you want to dump into this and if it's even worth it in the first place haha. I'm sticking with just one in the up-pipe. Seems like every tuner uses that method.

93forestpearl · Post by **93forestpearl** » Wed Sep 16, 2009 12:45 am

That's weird. Many have told me they prefer it as close to an exhaust port as possible.

ScottyS · Post by **ScottyS** » Wed Sep 16, 2009 1:10 am

You probably noticed the flat "buttons" in the casting just down from the ports on the driver's side. This is one location that is suggested by multiple sources. That's where I put mine.

However, while this gives a more accurate reading of the actual temps nearer the cylinder, it does not measure ALL of them, so if you have a, say, lean injector on the other side, you will never know. Also, this location eats probes fast.

I actually plan on putting another one in the up-pipe to use more long-term. I may run two at once for a little while just to get a baseline comparison.

The point for me is to get a measure for tuning that I can compare long-term, season-to-season, high elevation to low elevation. While the absolute number in the uppipe may be a little more meaningless (except for the turbo), the long-term relative trends are still worthwhile, IMO.

93forestpearl · Post by **93forestpearl** » Wed Sep 16, 2009 5:02 pm

I definitely agree that long term trends are what actually matter in the grand sceme of things. If one has a wideband along with knock detection, they are considerably less dependant on the absolute readings of the EGT probe.

Post by **Legacy777** » Thu Sep 17, 2009 5:37 pm

Thanks for the comments guys. I agree, the long term trends are really what's probably the most important.

I'm pretty sure I'm just going to go for one in the up-pipe. That will also keep me from having to tap the manifolds....just have to weld a bung on.

Post by **Legacy777** » Wed Nov 11, 2009 6:49 pm

Here's some pics of the defi EGT sensor I picked up.

http://main.experiencetherave.com/subar ... egtsensor/

I will be placing it in the base of the up-pipe.

The fittings that came with the sensor are a Bi-Lok thermocouple connector. The connector appears to be a compression fit to the thermocouple and 1/8" NPT on the other side.

Here's some info from Bi-Lok's catalog on the thermocouple connector.
http://main.experiencetherave.com/subar ... nector.pdf

I personally don't like the use of the NPT connection. NPT connections are meant to have some form of sealant used with them. Additionally, if a 1/8" NPT bung is used, the EGT probe will not be located ideally, with the tip of the probe being near the center of the piping.

I've decided to grind down the NPT threaded side of the connector to where about 1/8" is remaining, and have the connector welded to the pipe, with the remaining lip acting as a centering device for the hole drilled in the pipe.

I'm planning to do that this weekend, and will be dropping the up-pipe & bung off at a buddy's to be TIG welded.

Post by **Legacy777** » Sun Nov 22, 2009 10:47 pm

Ended up grinding down the fitting that came with the EGT sensor and had that welded to the up-pipe. I couldn't find a separate EGT bung that I liked and would fit. I just don't think a NPT fitting without sealant is going to stay sealed properly. Plus the additional fitting causes the probe to not be out in the exhaust stream as much.

Added pictures to the original link

http://main.experiencetherave.com/subar ... egtsensor/

Post by **Legacy777** » Mon Dec 14, 2009 5:05 am

Ran the wiring for the sensor while I had the fenders off. Added to the original pictures

http://main.experiencetherave.com/subar ... egtsensor/

Post by **Legacy777** » Thu Dec 24, 2009 4:55 pm

The EGT sensor is not working. I'm not sure what's up with it. But it was reading near 5v before even starting the car. So hopefully i can get that figured out.

In my opinion it's probably a bad sensor.....

Post by **Legacy777** » Wed Dec 30, 2009 12:38 am

Think I know the problem with the EGT sensor. It is a thermocouple and the changes it produces are in milli volts, not volts. So I need a type of amplifier to have it go from 0-5v.

This thing may work as long as I can verify the thermocouple type.

thermocouple amplifier

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EGT Sensor & Placement Questions

EGT Sensor & Placement Questions