installed cat-back

Dert · Apr 13, 2010

so I had my apexi cat back installed today, and I also asked for the cat to be removed and replaced with a test pipe. The shop said they would not remove the cat because of the o2 sensor behind it. My question is, can the cat be removed? Will the car not run well due to this sensor? :confused:

easy · Apr 13, 2010

it can be removed, the car will run fine, you will end up throwing a cel, though, and the reason the shop wouldn't remove it, is because it is part of the emissions equipment

nothingfiction · Apr 13, 2010

it will def throw a CEL at the least.

i don't know about the GST but on the 420A the o2 goes in after the cat. no complaints because its built into the cat-back exhaust not the cat/ i think the shop didn't want to remove the cat because it's technically illegal to remove properly working emissions from your car.

my dreamt dsm · Apr 13, 2010

The cat can be removed but your car is not going to run 100%. Plus an annoying cel light!

Achelea · Apr 13, 2010

It's against Federal Laws to remove an operational Catyltic converter. That said, you remove it and put in a straight Pipe, the O2 sensor after it will read it as the Cat's not working right and might pull the fuel trims for idle. Unless you have something to tell the computer otherwise, Keep it. At the very least, put flanges on it so if you want to take it to the track you could swap the test pipe in and still drive it home with the cat. but what do I know?

Ppayer38 · Apr 14, 2010

I just did my Turboback Exhaust and have a cat-delete DP in place so I have no cat and have yet to throw a CEL but I also used a Spark Plug non-fouler which seems to fool the o2 into thinking the cat is still there but only letting it get some of the exhaust gases. (Baiscally it is a mechanical fix instead of a eletrical) Im having no problem with fuel trims even though I didnt think the rear o2 did anything to fuel trims just check Cat effiency? I could be wrong though anyway it is an old trick ive done on a few cars and on some it works on others it works half the time

Going to have to say though flanged the Test pipe in place just as stated above by Achelea... It is much smarter just incase you get in trouble and you can remove and replace as needed/wanted

LiquidX · Apr 14, 2010

The only way the exhaust shop will "remove it" is if you tell them to put flanges on the CAT. Then tell them to flange a piece of straight pipe. They can remove it that way, but the CAT will be back on when you are to leave. They just can't take it off and leave it off as that's illegal.

As for the o2, there are special bungs that move the sensor further away from the exhaust stream and seem to work with the CEL.

rEclipserGST · Apr 14, 2010

Ppayer38 said:
I just did my Turboback Exhaust and have a cat-delete DP in place so I have no cat and have yet to throw a CEL but I also used a Spark Plug non-fouler which seems to fool the o2 into thinking the cat is still there but only letting it get some of the exhaust gases. (Baiscally it is a mechanical fix instead of a eletrical) Im having no problem with fuel trims even though I didnt think the rear o2 did anything to fuel trims just check Cat effiency? I could be wrong though anyway it is an old trick ive done on a few cars and on some it works on others it works half the time

Going to have to say though flanged the Test pipe in place just as stated above by Achelea... It is much smarter just incase you get in trouble and you can remove and replace as needed/wanted

I also have no CEL. I went with a ebay Cat-Back & ebay downpipe. Deletes the cat :cool:

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installed cat-back

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