O2 placement in 3" turbo back

[turboleg]

Hey guys. Wasnt sure exactly where to post this as ita engine exhaust and electronics all in one.

While my block is being built I decided to swap in one of my extra ej22t. I ended up with what I believe to be phil's old CES dp and full 3" ss exhaust. Since I have the engine out I figured I'd preinstall the 3"exhaust exhaust. But the O2 sensor is located after the DP in either the cat or the test pipe. Question is, will the change in length effect the stock ecu and give me negative results? I cant imagine it would be too big of a problem since the O2 sensor would still be pre cat.

[Legacy777]

If it's a CES meant for the US turbo legacy, it should have the sensor up by the turbo. Since you have it out, I'd probably just suggest having a SS O2 bung welded up to the stock location.

[James614]

I run an HKS downpipe with the O2 bung at the very back by the cat, no issues. I'd definitely suggest having a bung welded in the right spot though, the O2 sensor wires didn't like to stick with my soldering job and it took me 3 tries to get everything secured and insulated right.

[turboleg]

Hi James. Just so I understand, your O2 is Pre-cat correct?

[James614]

Yes, its a catless DP. I'm also running an open downpipe, so my last post shouild have read "where the cat would go". But either way, it runs fine at the very back of the DP, even though its not far away from atmosphere.

I doubt the exhaust composition changes much after the collector in the manifold before it hits any cats.

[turboleg]

I have the cat or the test pipe that I can run, so I could go catless if I want.

I too cant imagine there is a big difference. Especially since im going to a 3"exhaust. Seems the more restrictive stock dp would read at about the same point that a 3" dp would at the different locations.

[Dave_J]

The exhuast compsistion will not change much from just after the turbo to 3 feet away. It may cool down just a bit but the ratios of gasses should be almost the same. Put it where you can.