so i took of all my AIR/SMOG equipment and now im getting worried. About two years ago we put a new cat and flowmaster80 series with 2.5" pipe from the cat back. About 3 months ago I took the AIR equipment off and the past two weeks I have been hearing a weird sound from the exhaust. Its a coughing or choking sound coming from the cat, and at idle or low rpms I hear a rattle too, like a tin can. Should I get a two way cat or just a straight pipe? Will the removal of the cat make the car sound bad?

 

Im worried about this also......Anyone had any problems with their cat clogging????????

 

If you are using a 3 way convertor with the air tube then you removed the O2 supply from it when you removed the AIR tubes.In order to run without the pump supplying air to the cat then you have to run a 2 way cat.The rattling that you hear is the honeycomb coming apart inside the cat from lack of oxygenation(sp?).And cats do clog especially if the vehicle has a lot of miles on it.Or youv'e had an O2 sensor go bad and the motor was running rich.The new cats,even standard replacement,flow better(or are more efficent) than the ones that originally came on the cars

 

your cheapest route is to remove the cat and punch out the internals with a pipe and asledge hammer and hen reinstall it. it will change the tone of your car. wheather its better or worse will depend on engine size and mods. you may have problems at your next inspection if your state does emmision testing. or if you got a few bucks, you can put a new cat in there and dump that 2.5" pipe in the garbage that you have on there now. I think Napa sells a 3" int. pipe for our cars cheap.

 

dont know what a 3" inch anything would do in my 305 with the stock heads. You can lose alot of vacuum if you run an exhaust setup too large for your car. Rule of thumb is kinda like 2.5" for 305 and 3" for 350-up. Alot of people just think bigger is better, but when you start having vacuum problems that becomes incorrect.

 

I just experienced this. After 3 years and 43 dyno pulls this weekend my catco3 way with NO AIR hooked up is fainlly smelling and ratteling like no tomorrow. I suspect it is no burned out. Since Ohio is doing away with e-chek by the next time I need to go, its getting punched out. I do have a straight pipe but its raspy.

 

Mkos1990, So is it clogged, or burnt out???? How has this affected your horsepower output???? Will someone please tell me about the 2 way cat??? Not sure if I have the terminology correct....Can you just drop one in, and then get rid of the air tubes??? Thanks, Tom

 

I dunno. Havent looked into it, but its coming out soon. I just havent had time for the car.

 

My cat was clogged so bad that exhasut was pushing out of my manifolds with a constant loud woosh sound. It was so bad it couldnt even beat my freind 17 sec. integra. So i had it removed and my 1/4 mile time improved from a 15.82@84.43mph to a 15.41@88. I'm sure some people need to keep it for emmission reasons...

 

The 3 inch pipe being installed will help your performance not hender it. I agree with the 2 1/2 rule for the smaller displacment motors but that only applys for a dual exaust and since our cars do not come factory with duals then upping the single piping to 3 inch helps out a lot!

 

My smog pump has also been romved and I suspect my cats are clogging.
Is ther any down side to hollowing them out?
also ther is no emissions in my part of the state,so this would be legal.

 

If you cat is "clogging", it's for some reason other than A.I.R. removal.

After installing 2055's and a 3" Catco, my A.I.R. pump froze up on me. I left it off until I needed to go through emissions testing again, 2 years later. I got another pump, hooked the system up, got the tune-up in order, and went in for the test. It was cleaner than the stock system ran.

 

well my cats are original from 1989,i may just be paranoid.but if i hollow them out would i gain or lose anything,is it healthy for my engine? would i want a custom chip?

 

I had a rattling in my cat so I punched it out. I gained alot of power out of it. It sounds alot nicer then it did before.