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The o2 Spacer Thread

GTI Jake

Autocross Champion
Location
Charlotte, NC
Nobody’s going to guarantee no CEL, even AWE doesn’t after one year if you read the fine print. A cat is a wear item and while they can last a very long time, abuse can also lead to them degrading faster than you’d expect so this is no fault of AWE or any other manufacturer. Bottom line is wear items don’t last forever, so keep that in mind.

You need to understand what you’re attempting and go from there. Read this part carefully:

By adding an o2 spacer you’re simulating the large restrictive OEM cat being there by pulling the sensor out of direct flow and or restricting how much gasses are allowed to reach the sensor. There’s no one size fits all solution, hence why nobody’s going to guarantee it’ll work on the first try and forever on afterwards.

General starting points:

Catted downpipe with the cat BEFORE the o2 sensor = Vibrant Adjustable straight spacer with medium or large insert depending on the cell count of the cat (higher cell count 300+, use large. Lower cell count like 200 use medium). Vibrant has discontinued this spacer as of December 2020

Catless downpipe or catted with the o2 sensor before the cat = Vibrant adjustable J spacer with the medium insert, pointed as up stream as possible.

There are different codes associated with different issues that can guide you to correcting the CEL if you still get one, so don’t get frustrated or start buying different spacers if it doesn’t work on the first try. I’ll get into that more later.

Also, keep in mind a “drive cycle” is roughly 100-150 miles and needs to be completed before you know if your spacer worked at defeating CEL. The EPA requires this so you can’t reset a CEL in the parking lot across the street from a testing facility and rush over to pass before the fault returns.
 
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Agray

Go Kart Newbie
Location
Washington
Thanks for posting, I’ve had good luck with the vibrant spacer. Understand a cat is a wear item. If I drive like a reasonable person 80% of the time and 20% like a goon, how long do you think a stock cat would last compared to a 200 cell cat? What happens to a cat when it “wears out”?
 

GTI Jake

Autocross Champion
Location
Charlotte, NC
Thanks for posting, I’ve had good luck with the vibrant spacer. Understand a cat is a wear item. If I drive like a reasonable person 80% of the time and 20% like a goon, how long do you think a stock cat would last compared to a 200 cell cat? What happens to a cat when it “wears out”?

Ive never personally worn out a cat, but the substrate isn’t invincible and it’s condition directly effects what the downstream o2 sensor reads. If a cat/spacer set up is just barely meeting the minimum requirements and slowly degrades to the point of popping a CEL it’s not voodoo magic. The OEM cat will wear out over time as well, but the o2 sensor readings are based around it and not just on the tipping point of the scale like an aftermarket set up might be.

Normally for a cat to be damaged a different issue is the cause, like excessively rich or lean AFR. Your driving habits won’t likely have a big effect on it unless it’s to the extreme like a full blown rally car or something running excessive EGT
 

SVTunit

Ready to race!
Location
Michigan
I have the APR catted DP and had luck with the Vibrant J spacer using the smallest hole insert (med. and large hole inserts triggered a CEL).
 

jay745

track sl00t
Location
Chicago
Car(s)
2 vw's
Nobody’s going to guarantee no CEL, even AWE doesn’t after one year if you read the fine print. A cat is a wear item and while they can last a very long time, abuse can also lead to them degrading faster than you’d expect so this is no fault of AWE or any other manufacturer. Bottom line is wear items don’t last forever, so keep that in mind.

You need to understand what you’re attempting and go from there. Read this part carefully:

By adding an o2 spacer you’re simulating the large restrictive OEM cat being there by pulling the sensor out of direct flow and or restricting how much gasses are allowed to reach the sensor. There’s no one size fits all solution, hence why nobody’s going to guarantee it’ll work on the first try and forever on afterwards.

General starting points:

Catted downpipe with the cat BEFORE the o2 sensor = Vibrant Adjustable straight spacer with medium or large insert depending on the cell count of the cat (higher cell count 300+, use large. Lower cell count like 200 use medium).

Catless downpipe or catted with the o2 sensor before the cat = Vibrant adjustable J spacer with the medium insert, pointed as up stream as possible.

There are different codes associated with different issues that can guide you to correcting the CEL if you still get one, so don’t get frustrated or start buying different spacers if it doesn’t work on the first try. I’ll get into that more later.

Also, keep in mind a “drive cycle” is roughly 100-150 miles and needs to be completed before you know if your spacer worked at defeating CEL. The EPA requires this so you can’t reset a CEL in the parking lot across the street from a resting facility and rush over to pass before the fault returns.


I've had good success with my 42DD spacer when I need to pass emissions. I take it out right after I pass though and don't keep it in year round. I'm not sure on mk7's but mk5 and mk6 you could force readiness with VCDS to avoid having to drive around for 100 miles. Not that I've ever forced it around the block from the testing station or anything....... 😇
 

arrrgh14

Ready to race!
Location
US
I have the Vibrant spacer installed but I’m also stage 2 so I don’t really need it to defeat the CEL.... I just kept it in there after I installed it to pass inspection. Any issue with leaving it in there or should I take it out with the tune installed?
 

GTI Jake

Autocross Champion
Location
Charlotte, NC
I have the Vibrant spacer installed but I’m also stage 2 so I don’t really need it to defeat the CEL.... I just kept it in there after I installed it to pass inspection. Any issue with leaving it in there or should I take it out with the tune installed?

Depends on who’s tune. Some don’t use the secondary o2 sensor at all, and some still use it for long term fuel trim data like stock. Probably best answered by your tuner, but highly unlikely it would be an issue to leave it as AFR is read on the primary/wideband
 

crxgator

Drag Racing Champion
I still do the spark plug defouler trick. Been working on my gutted downpipe setup for 5k miles.
 

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
Depends on who’s tune. Some don’t use the secondary o2 sensor at all, and some still use it for long term fuel trim data like stock. Probably best answered by your tuner, but highly unlikely it would be an issue to leave it as AFR is read on the primary/wideband

I don't think that any tuner uses the second 02 sensor for tuning. I know that EQT doesn't because they claim leaving it plugged in will cause your engine to run rich over time. Ed says to just unplug it.
 

yirayira

Go Kart Newbie
Location
Chicago, IL
Car(s)
2015 GTI SE
I’ve never tried it, but I don’t believe mk7 will allow you to force it

I have set readiness and successfully passed emissions on the MK7 with VCDS automatic test sequence -- IDE00553
https://www.ross-tech.com/vcds/tour/readiness.php

This may just be semantics but it's an important distinction, "There is no way to "Force Readiness" on any vehicle. You may be able to force certain tests, but there's always the question whether all proper conditions have been met."
https://forums.ross-tech.com/showthread.php?16102-Forced-OBD-readiness-with-VCDS
 

yirayira

Go Kart Newbie
Location
Chicago, IL
Car(s)
2015 GTI SE
I've heard good things about catted spacers if you're getting codes thrown.
I consider myself lucky I haven't had any issues with a CTS and a generic 90 spacer

https://www.fabspeed.com/universal-o2-spacer-with-catalytic-converter-single/


I don't think that any tuner uses the second 02 sensor for tuning. I know that EQT doesn't because they claim leaving it plugged in will cause your engine to run rich over time. Ed says to just unplug it.

I thought the LTFT issues with the secondary O2 was Cobb specific, do you know if it impacts other tuning platforms?
 

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
I've heard good things about catted spacers if you're getting codes thrown.
I consider myself lucky I haven't had any issues with a CTS and a generic 90 spacer

https://www.fabspeed.com/universal-o2-spacer-with-catalytic-converter-single/




I thought the LTFT issues with the secondary O2 was Cobb specific, do you know if it impacts other tuning platforms?

I'm guessing but logically it would be the same for all tuners. I'm testing with it unplugged now and after two weeks I'm going to connect it again to compare. I'm primarily testing MPG because as far as performance is concerned there's no difference.
 
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