So I have a bunch of car parts for my car already. Obviously I plan on tuning professionally, right after installing, but I’m afraid that’s it’s going to throw a CEL. Currently, I have an invidia exhaust on it, but I plan to install a downpipe, BOV, and a CAI. I’ve been told by a couple pro tuners that it may throw a code, but an o2 spacer would help. Has anyone ever had to do this and does it work?
Ruedebusch
What year is the car. the 2019?+ are supposedly more sensitive.
If you're putting in a vent to atmosphere BOV you really should get a tune along with converting to speed density. Honestly if the car is semi recent there isn't a whole lot to be gained with a catted/catless downpipe. Modern cats are pretty good, and you don't have to worry about emissions BS.
Yes O2 spacers can work, better chance of success on older model years, also depends on the quality of the aftermarket catted downpipe, if that's what you're getting.
You can always do an opensource tune and defeat the CEL.
O2 spacers are cheap (under $100) and you only need one. There's a company in Canada that sells O2 simulators that have a better chance of working.
Also the ECU does some adjustment of long term fuel trims based on the rear o2 sensor, so you can end up in a bad spot if you're using a spacer/defouler.
If you're putting in a vent to atmosphere BOV you really should get a tune along with converting to speed density. Honestly if the car is semi recent there isn't a whole lot to be gained with a catted/catless downpipe. Modern cats are pretty good, and you don't have to worry about emissions BS.
Yes O2 spacers can work, better chance of success on older model years, also depends on the quality of the aftermarket catted downpipe, if that's what you're getting.
You can always do an opensource tune and defeat the CEL.
O2 spacers are cheap (under $100) and you only need one. There's a company in Canada that sells O2 simulators that have a better chance of working.
Also the ECU does some adjustment of long term fuel trims based on the rear o2 sensor, so you can end up in a bad spot if you're using a spacer/defouler.
If they made a bellmouth conversion for the stock DP, I’d probably rock one on my 19 and see what the stock cats could do. That OE DP flange is just a head scratcher….
A downpipe + tune yields a pretty big overall benefit. That scales up as turbo/power will scale up. But a downpipe itself is one of the best bang for the buck mods you can get on our cars.
Running a 2021 STI fully built engine….
The down pipe is a Tsudo 3” bellmouth with a 200 cell ceramic cat primary. Added a “mini o2 cat/defouler” and would get an p0137 code. I then added a GESI GEN2 400 cell cat downstream from the 200 Cell cat inline with the “defouler”. Still got a p0137 code. The second o2 bung is downstream from both cats where it connects to rest of the Cat back exhaust. I removed the “defouler” because it was designed to remove pO420 codes, not p0137 codes. Bam. No CEL. Problem solved.
Just my 2 cents. Spent about half for what other downpipes that have a GESI GEN2 cat attached.
Good luck. Reach out to @yamahaSHO for tuning….
The down pipe is a Tsudo 3” bellmouth with a 200 cell ceramic cat primary. Added a “mini o2 cat/defouler” and would get an p0137 code. I then added a GESI GEN2 400 cell cat downstream from the 200 Cell cat inline with the “defouler”. Still got a p0137 code. The second o2 bung is downstream from both cats where it connects to rest of the Cat back exhaust. I removed the “defouler” because it was designed to remove pO420 codes, not p0137 codes. Bam. No CEL. Problem solved.
Just my 2 cents. Spent about half for what other downpipes that have a GESI GEN2 cat attached.
Good luck. Reach out to @yamahaSHO for tuning….
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