CAT question

HardCore97 · Post by **HardCore97** » Thu Mar 05, 2009 4:52 pm

shit i just got one for 40 bucks new lol i might have to turn around and sell it

99SilverCX · Post by **99SilverCX** » Sat Mar 07, 2009 12:27 am

RyanA;169094 wrote:Just get a REAL aftermarket cat (not high flow POS that is resonator) that is the stubby one. Get one that is 2.5" ID. The shorter cat fits pretty well. Have your cat back on the car and the header on there. Put your flange for the header on and a flange for the cat back and put the stubby cat in the middle. Add little pieces of pipe, if needed, and weld up. If you don't use a flex joint, you need to make sure you use spring bolts so the exhaust has somewhere to move. You can put the rear O2 behind the cat or in the back of it. Either way will let it make the ECU happy.

I was thinking about putting the O2 bung behind the cat, but was wondering it the ECU would have liked that because on the SI the O2 is in the middle of the cat.

HardCore97;169118 wrote:heres a magnaflow cat for 65 bucks CLICK but you will have to run an o2 sensor behind it since it doesnt have on 02 bung

Yeah, that's what I had on my OBD1 setup.

I was actually wondering it it's worth spending extra $12 on a cat like this: Magnaflow because it has an O2 bung already. Cuz otherwise I'll have to pay the shop to put in the extra O2 bung.

RyanA · Post by **RyanA** » Sat Mar 07, 2009 1:27 am

Factory cats are worth good money; aftermarket ones are not worth anything. They don't use nearly as high of platinum content as OEM style cats so the value is way less (5-20 bucks each VS 50-125 each)

The ECU is simply looking for an acceptable difference between the front and rear O2 sensors to verify the converter is doing its job. This is why some people run spark plug foulers between the exhaust and rear O2 after gutting a cat...