Straight Pipe in Place of Cat?

WhosYoDaddyKoo00 · #1 12-09-2006, 09:22 PM

Hey, I was wondering if I replaced my cat convertor with a straight pipe would it effect my ECU? I know that the o2 sensor is before it, but is there still a chance that it would be effected by the loss of backpressure, or in any other way? If its a legit mod without screwing up with ECU, what would be the diameter of the straight pipe? And how long?

ikeyballz · #2 12-09-2006, 10:48 PM

use the same dia. as your cat. and get a ''test pipe'' they have a place where you can screw in your O2. it wont do much, although i heard you do have to change some stuff on the ecm? someone with more knowledge?
and.. make sure its a.ok for your smog.

goldz28 · #3 12-09-2006, 11:10 PM

Do you have emissions? If you take the cat or cats off you will need to have someone tune out the rear o2's or you will get a code and your check engine soon light will come on. The rear o2s have nothing to do with how the car runs just makes sure the cats are doing their job. I read that getting rid of your cat takes 3% or so of the back pressure so you get alil better flow.

Hope that helps

WhosYoDaddyKoo00 · #4 12-09-2006, 11:21 PM

No offense, I'm not trying to disregard your advice, but I wanted to know from someone who may have done it already. And we dont have emissions tests in Michigan.

97cavalier · #5 12-10-2006, 12:08 AM

You don't always get a gain with it. Some people have actully lost hp when they have did this.

goldz28 · #6 12-10-2006, 07:42 AM

Quote:

Originally Posted by WhosYoDaddyKoo00

No offense, I'm not trying to disregard your advice, but I wanted to know from someone who may have done it already. And we dont have emissions tests in Michigan.

Non taken, I don't have any cats on my car. The ECU is not effected in the way the car runs but you will get a check engine light due to the fact the car thinks the cats are not working properly or the o2 sensors are not working. There are no emissions in Oregon either.

I noticed the car ran better and the sound was louder.

What size of engine do you have?

Savage Messiah · #7 12-10-2006, 02:00 PM

A benifit you will notice if if you remove the cat and then tune it, you can delete the COT protection (cat over temp, dumps in extra fuel at WOT since going lean kills the cats), allowing you to tune it a tad bit more lean and therefore increase the power, and also saving fuel (although at WOT who cares about gas mileage lol), and reducing the overwhelming cas smell of a catless car

What I'd do is this: get a bullet muffler instead of a straight pipe... that way it'll quiet it down some.

WhosYoDaddyKoo00 · #8 12-14-2006, 11:55 PM

Well, I just figured I wouldn't get a check engine light 'cause the o2 sensor is before the cat. I'm guessing that it is possible for it to notice if one was gone because of pressure

, but I dont know. Well, my engine is a 3.8litre, 3800 engine to answer Goldz question.

Savage Messiah · #9 12-15-2006, 01:48 AM

there's an o2 after the cat and the only thing it does is make sure the cat is working fine. Tune that out via hptuners, texas speed, PCMFORLESS, etc and no problems

jtvyper456 · #10 12-18-2006, 01:49 AM

I've cut the cat out of my 3.4, haven't got any lights (knock on wood), and it's been out for over 6 months now! Sounds deeper, but with the lost backpressure, the muffler will 'pop' or rattle if you accelerate up/around 3000-3500RPMs before it shifts, only reason I cut mine is because it had fallen apart in the casing, and made the car sound like a rolling can when idling.

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