I have a '93 XLT w/ KKM intake and cat back Flowmaster exhaust. I want to inprove ponies and sound. I had a straight pipe made to replace my cats. I am worried that I will get a fine or it will sound like crap. My exhaust now sounds pretty deep. I want it to be a little louder and more throaty. Would a high flow cat resolve my problems?

At least it would be legal and environmentally responsible again ;)

Doubtful that you would benefit from either, The removal of cats is against the law' remember YOU breathe the air too.

i had a garage redo my exhaust with 2 1/2 pipe(i think) and a flowmaster. When i got it back he said he gutted both cats also. It sounds nice but it will never pass inspection again. Now when december comes around again i have to find a garage to pass my truck.:mad: Get hi flow cats if anything.

Why do u need to get it inspected? Do you live in California or something? They dont do that where i live. And if u need to get it inspected, go to the garage that gutted your cats! Does it sound raspy? Or does it sound low and throaty? Thanks man

The right thing to do would be to put the cat's on. I also live in Iowa and have never been inspected, nor do I know of anybody that has been inspected. Some of my friends have taken their cats off, but they did it bc they have high horsepower vehicles and completely replaced the stock exhaust. I doubt the cats are restrictive unless they are clogged, and I don't think they change the sound that much, but I'm not very sure about that.

my responsible side says to run hi-flow cats. However mine clogged up this past summer and cash was short. Amazing what an impact with a big hammer and bar can fix. I'll replace it when when I finally have the $ for the 5.0 transplant, but I'm not spending any big money to fix something that's no longer broke.

:chug: :chug:

Replace the cats.

The truck will run and sound fine without converters.

Does it increse horespower or not?....that is an arbitrary question until someone comes up with a dyno sheet from a 4.0 with no cat vs the same motor with a cat. I don't believe anything helps performance unless I can see a dyno sheet. If you think that getting headers and a cat back system will make the truck faster, then the same logic suggests that gutting the cat will help performance also. It is along the same lines of modification; and that is decreasing backpressure.

Some people say "putting in a straightpipe hurts the motor" and at the same time mention "a hi-flow catalyst/exhaust system are what you need; they increase performance". These people are full of shit.

No, a cat will not help your top end hp. However, due to the restriction it puts in the flow it may give you more low torque vs a straight pipe.

Besides the fact that not running cats is totally irresponsible IMO.

Originally posted by Alec
Besides the fact that not running cats is totally irresponsible IMO.

... and illegal.

I assume you have a v6 so have high flows on. If you want it very obnoxious sounding, cut them off. If you don't have emissions, don't worry about it. Everything these days seems to impact the enviornment somehow. It is illegal in all fifty states, but if you don't have checks, they have no way of finding out. What they don't know don't hurt.:)

Cutting out the cat will not make the truck sound obnoxious. The difference in sound is similar to that achieved after installing headers.

The guy's original question had nothing to do with the legality and environmental issues that arise with cat removal. He obviously knows that it is illegal, because he is worried about getting a ticket, and everyone is aware of the purpose of the cat. This thread's purpose was to have a technical question answered. It was not started to conjure an EPA comittee meeting.

Won't removing or gutting the cats trigger a CEL/MIL? Or don't the 93's have downstream O2 sensors?

If you have a downstream O2 then yes, you would have to fool the O2 to not throw a CEL and run crappy.

took out the cat on my dads 77 vette cause it was stealing hp. after wresteling with it for a few days, finally got it off. he was going to have a pipe made, but couldnt find a shop to do it :( so we put in a new cat and he says its like driving a totally different car. keep in mind that this cat was 26 years old...

The O2 sensor(s) on 93's are upstream.

It's so funny coming from a Camaro forum where everyone is all about going off-road y-pipe to here where everyone seems really serious about the smog thing. My car bows a little bit of smoke as it is so I doubt tearing off the cats would make much difference. I think I might actually cut them out tomorrow. I had a truck with no cats and it sounded great.

If you have a downstream O2 then yes, you would have to fool the O2 to not throw a CEL and run crappy.

O2 sims or someone to delete the code for you.

I replaced my cats with a bolt in straight section and i like the way my explorer runs/sounds. The straight section has never cause a check engine light

jesus this post was dug up from 4 years ago haha... my 2 cents tho, removing the cats will def improve airflow but u r sacrificing plenty of low end torque... if u do a straight pipe and the pipe is pretty large then ur probably not helping ur engine at all and making it wear and tear faster... if u dont have the performance parts for this thing to handle a straight pipe then its probably doing more harm than good... hi flow cats will give u the low end back and still give u plenty of torque on the high end because u dont have the crappy stock muffler in there