RK951

Its been a while but a few people have described using the C02 test port bung on the top of the crossover pipe to mount an EGT probe. Could someone who has installed an EGT probe in the CO2 test port on the crossover pipe comment their install?

From what we could figure out, a 3/16" in probe will fit perfectly however the space above the bung is limited. For the probe tip to end up in the center of the pipe using the C02 test port bung, the best guestimate for the correct EGT probe hot leg length is 1.8inches. This means ~2.3 inches (hot leg length + .5inches for bend in probe) of space above the top of the bung is required so that the probe could be inserted. I guess a shorter leg length could be used but it would be nice to try and position the tip in the middle of the pipe.

Could someone who has their car up in the air have a look at the CO2 test port and measure how much clearance there is? Since the test port is likely connected, it would probably be easiest to measure from the top edge of the crossover pipe next to the bung and we could subtract the height of the bung.

TIA

ross255

Well i cant help you with the measurements.
But I would like to know how much will the temp difference be by monting the sensor in the co2 test port, instead of as near to the exhaust port as possible.
If it still gives accurate readings, then I might consider a similar install

Edman951

I tried to fit the probe that come in the autometer egt gauge.
And it doesn/t fit.
Its way too long, and you can/t even get it into the pipe because of clearance between the pipe and the motor.
Plus you have to use a diferent a metric adapter to match the factory threads.

TRP951

i thought it wouldnt be accurate there is what people have said? Why not pull the headers and drill the heat shield and weld a bung on #2 runner?

Epic2112

If I remember correctly, the ideal place is withing an inch or two of the exhaust port.

Duke

Or right after when all the cylinders are merged.

RK951

Using the C02 test port is not a new idea and has been done. No one is arguing the merits of being directly on the cylinder exhaust port but its not an option at this point in time.

As I mentioned above, the "bunghole" (what a great word) will fit a 3/16" diameter probe as I've already tried it on a pipe not installed on a car. The probe that came with your Autometer gauge and my VDO gauge is 1/4" and definitely won't fit. It's also probably a straight probe and not right angled as I stated above. You are correct, a straight probe will never clear. Lastly, all that it required to use the standard bung is a cap with metric (M14) threads. According to the eclou in the thread below, the thread is the same as wheel stud lugnut.

https://rennlist.com/forums/showthre...&highlight=EGT

Laust Pedersen

The “ideal” solution is 4 EGT’s as close to the exhaust ports as possible. That unfortunately is quite labor intensive (=costly) to install on an assembled engine in good condition and in my opinion a single fast reacting EGT installed instead of the test tube is still a good solution. It will not get the same high numbers as an EGT installed near the exhaust port, but will probably be close enough (90 to 95%). It certainly will be a good relative diagnostic tool, telling if the engine has changed from one day to the next.

Rick, since the probe we have under consideration is an “exposed tip” type (only very slightly affected by wall temperatures), I think it is adequate if the tube protrudes only ½” into the pipe. Due to the bend, there may not be much flow at that depth, but it should have the same temperature as the rest of the exhaust gas in that area.

Laust

RK951

Thanks Laust. I'm going to try and get the car put up in the air on Tuesday morning and measure the amount of maximal clearance and then order a EGT probe with the optimal hotleg length.

ApexCars

Once you find the right probe, please let me kown because I also want to install one there.