I'm going to run CAT bypass pipes during track season. Any of you guys using Oxygen sensor bung extenders on the secondary cat efficiency O2 sensor? If so, what type? Are those effective at fooling the system or do you have to get the CEL coded out anyway?

Thx...

 

I tried the 90 degree extenders when I installed a catless exhaust. Car Still threw check engine codes and car actually ran slower. I don't think the secondary O2s were seeing enough exhaust and so the ecu compensated buy adding more fuel, it was pig rich.
It was a waste, in the end I got a tune for no cats and the car has been running awesome, even passed inspection.

 

Unless I'm mistaken, the secondary cats don't have anything to do with how the car runs, they are strictly there for cat efficiency reasons. The primaries are responsible for making sure the car runs optimally.

 

I used them on a 99 Z28 Camaro years ago and it worked.

 

Thats what I thought also, but I have logs, the car ran stupid rich.
Macaster also confirmed it.
The secondaries check to make sure the cats are working. If they don't see enough exhaust or too much (like when you remove cats) the computer adjusts the S/T fuel trims... Mine was adding 7-9% fuel.
Tuners can phase them out to make sure they don't affect anything.

 

i ran the angled ones w decats but also had cels. replaced my pre 02's and removed them. never a cel since or need to mess with anything else ( same old tune etc..) still very richly decatted.

 

Hound,
I ran the angled on the secondaries but would get a cel. But after clearing the cel a couple of times, they went away. If you want, I can look up where I got them on ebay.

 

I ran the extenders for a bit. Don't, they don't work and they do mess with the primary O2 readings. I was throwing 1145 codes as well as 1155's(which is a primary O2 code) and my car was running pig rich under WOT.

Just get someone to deactivate the secondary O2 codes and you'll be golden.

 

thats only if you dont have to pass emissions in his state

 

I tried 3 different type of extenders, CEL eventually came back. Have not tried the mini cat extension as I've read they don't perm solve it either.

 

I've been running straight pipes for a while now. You can get the o2 extenders...they might work for a little bit for suppressing the CEL, however, it usually does trip it after time.

I've no issues with my primary o2 sensors....on pump or race gas. A tuner can disable the CEL.

 

And if you want the car to run correctly...
If your car is stockish or or ur tune hasn't cancelled the 2nd O2s out it WILL affect the fueling/performance if you go catless or use extenders or mini-cats, etc.,

 

I was just about to buy extenders but having seen this thread it seems they won't work!

I occasionally get the CEL (P0420 - cats system efficiency below threshold).

I am running cargraphics exhaust (cats still in place), and tune (1.0 bar sustained 1.3 peak). I clear the code but it comes back.

I understand this is the cats tiring and will only get worse and more frequent.

Car runs great and passes the smog test with flying colours, so it really pisses me off if I will need to get new cats.

Can a tuner really permanently stop just this type of a code from reappearing?

 

I started getting codes when I switched to a SpeedTech exhaust. Once I got a tune the codes have never returned. More power, no codes - Win- Win.

 

Can you explain further? My ST/LT fuel trims have been dead on while running no cats with no CEL.