I'm gonna run cat bypass pipes during track season as my car does not really see any street use. Any of you guys have luck with any of the secondary O2 extenders. I know I can simply turn the light off but I think it would be better if the ECU was not seeing any issues. I know there are endless types on the internet from straight to 90º types, to those with mini cat inserts. Looking for real world experience with particular spacers, not theories. Sam had sent me a like for some but curious what others have used successfully.

Thx..

 

The set that came with my EBWerks exhaust worked perfectly, I drove for a month or so with them before I got a tune and no light came on- at that point Sam turned it off anyway while he was setting me up.

 

Was it a straight or angled extender?

 

Straight... Between 2-3 inches long if memory serves. Might have a pic around here, or I can go under the car and grab one when I get home this evening.

 

I installed a catless exhaust soon after I bought my car and I tried both the mini-cats and 90 degree extenders on a stock tune and the car ran like crap. CEL's would come on. I would clear but withing 500 miles would come back. The car also ran very rich as I don't think the rears were seeing enough emissions, car was actually slower than with the stock exhaust.
Eventually I got a tune and they phased the rears out and no CEL. Car ran/run great.

 

That's strange. My understanding is that you don't "tune" out the rear O2 sensors, you only shut off the CEL light in the dash and that's it. The primaries are what is what the ECU is looking at for AFR control. The secondaries are for cat efficiency. Maybe Sam can chime in and explain.

 

Best way would be to numb the sensitivity range of the rear O2. I run cats on my car and haven't been able to pass roadside sniffers despite being stoich, running E85, and having decent timing. Can't plug-in with a standalone and am looking for a solution. My previous tune passed fine but I've not got my DME and am now not running a MAF. Nightmare! I'm interested in what you find out with extenders for sure!

 

Numbing down the sensitivity is what I'm thinking and what my tuner advised is running catless. I'm thinking of trying the FVD extender here:

https://www.fvd.net/us-en/FVD111LAMA...extension.html

Talked with Sam earlier and he gave me a link for this J extender:


My main goal was to shed a little weight from the back of the car but I'm not willing to do that if deleting the cats will negatively effect the drivability of the car.
I guess I can try it and reinstall the cats if need be.

 

I am catless John but have my CEL tuned out...so not much help but whatever

 

Nope that is not entirely true. The ecu expects to see something downstream and compensates the fuel trims based on the secondaries also. I have logs to show it. Basically when I put the mini cats the 2nd o2 sensors weren't seeing enough emissions and so it added almost 10% to the FT. It thinks there is something wrong with the cats.

 

So basically it sounds like unless you get another custom tune for catless the car is going to run like shiat. Not sure I wanna go down that route. I thought it was simply a matter of shutting off the nuisance light.

 

Can straight an 90 degree on 2 exhaust systems I build, no issues running like that.

 

Why not call your tuner to see if he will help you out. Ask if it is a big deal or not to change that up.

 

properly done, turn off the rear o2's altogether... readiness isn't active/checked for emissions

 

The ECU can be setup to run with disabled cat diagnostics without any issues at all. That wouldn't be a problem and personally I have not seen any car with fueling issues because of disabled secondary O2s.

My advise would be to run large 100 cell cats for environmental reasons. The power and spool difference between these cats and no cats is not really something to worry about. Depending on cat efficiency it may still be necessary to disable rear cat diagnostics.

I have passed emissions with my 100 cells last week.