egt probe in up-pipe or manifold??

[Jerry Seagreaves]

Just curious there is alot of debate at proper installation...I know that the manifold gives the proper numbers because it is not combined gases like the up-pipe, but can you still get accurate readings by installing at the up-pipe? I heard this way is common also....I just want to make sure that it will still work.
Jerry

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[wcbjr]

2" - 3" off the heads on the #3 or #4 runner.

[Chunky_Chicken]

I read my EGT's from my uppipe, they are about 50-70 degC lower than from the manifold.

I chose the uppipe over the manifold for three reasons:

1. I was worried about the expansion and contraction of the manifold leading to the probe backing out, or even the manifold cracking. I've seen a manifold crack due to a hole drilled for a probe, but IMO it was drilled improperly, and not on a casting button (which is a pretty safe place on the WRX)

2. Putting the probe in either bank's manifild only monitors two cylinders. If something were to do wrong on the other bank (ie: injector failing) it wouldn't show up and could go undetected untill failure.

3. Putting it in the uppipe means I can return the car to stock without having to plug a suspicious hole in the manifold and heatshield.



The meter will read faster closer to the manifold, but not because the gas hits it first and the uppipe seconds later (the time it takes to go from the head to the turbo is extreamly short). Heat transfer rate is due to a temperature differential. The larger the difference in temperature, the faster the rate of temperature change at the probe. That basically means that a probe will react faster to hotter gases. Given that there is about a 50-70 degC difference, you will get a faster response at the manifold. The actuall difference in resonse time I don't know, but I'd estimate it to be under 1.0s which on a mildly tuned car is acceptable IMO.


-Pete

[CirrusWRX]

Those are some very interesting points Chunky - haven't really read any "pros" of not putting it in the manifold, but after reading yours, it seems like another viable option. Good stuff!

[Jerry Seagreaves]

so what do you guys do with the stock egt sensor?
Jerry

[Chunky_Chicken]

Originally posted by Jerry Seagreaves
so what do you guys do with the stock egt sensor?
Jerry

I have my Defi EGT probe about 25mm below (before) the factory EGT switch. I wouldn't have bothered putting the factory switch in at all, but the uppipe came with a bung, and rather than seach for a plug, I just stuck the probe back in. The resistor mod seems to work very well when you eliminate the factory switch.

-Pete