mlm0

Brand new cat. Will it cause a problem to cat if I don't hook up air tube.
1989 stock with auto trans. Removed air pump

HAD2HAV2

In that case just plug the cat tube.

aklim

Wish you asked that question last year. I tossed out 2 plugs that were for my Random Tech cat that I haven't used for eons. But to answer your question, it depends. I would say it is ok if you plug it up so crap doesn't get in but I would not leave the tube to vent to atmosphere.

gjohnson

Why did you put on a new cat if you took off the air pump?They work together

mlm0

I haven't bought it yet. Wanted to clean up engine compartment while I'm waiting for cylinder heads to get back from shop, so I removed air pump and egr system. I bought cat test pipe off eBay to replace cat last year, but just tried it and it does not fit. I don't want to put old cat back in, so I am thinking about just putting new one back in

aklim

https://en.wikipedia.org/wiki/Secondary_air_injection

AIR system makes it more efficient so it can function without it, just not as well. I run it without the AIR because I want to cut down the noise which the hollowed out cat made plenty of and it cleaned up the engine bay for me to work on without the tubes running to the headers.

odxr

I would just get a local muffler shop to weld up what you need-a straight pipe with the correct flanges.You can have them cut the flanges off of an old cat and make a custom pipe.Less heat under the car.The only way I would run a cat is if I had to pass an emission inpection.

aklim

Besides the emissions inspection, it will make more noise which attracts all sorts of undesirable attention from ricers and cops. Once a cop stops you, they have a reason to go fishing on your dime. I had a 2.3 Turbo with a loud exhaust and every so often, going through some small towns, it does attract cops or at least make them look at you. In the neighboring town, they will dyno tune your Harley BUT if they see you have anything aftermarket on the exhaust, you have to sign a waiver and the cops are sticklers on noise.

odxr

The op is in Texas.Texas is not a nanny state like Komifornia or the east coast.I buy mandrel bends and build my own exhaust systems.I am not a big fan of cat convertors.Until cars with obd2 came out they were really just a mop-up device for people that are too lazy to keep their cars in tune.I prefer to burn my gas in the engine.If you put a 3" glass pack muffler where that cat was and left the rest of the exhaust system stock you would have a very nice sounding car.If you gut convertors out and install the empty shells you get unplanned noises.

aklim

I have never tried OBD2 cars myself but we had a car that was in tune that we did a test on in class. That was over 15 years ago but the tailpipe sniffer definitely picked up more emissions without the cat than with. So how are you defining "in tune"?

Prefer all you want but you aren't getting everything burned in the engine unless you can make it have perfect combustion.

I agree that gutting the cat makes all kinds of noise but how is the glass pack going to muffle it down as well as the cat? I've heard them on Mustangs and F-bodys and they are more noisy than the stock exhaust system which is the exact reason they were put on. To make more noise and sound like a race car of the past did.

odxr

If you just welded in a straight pipe where the cat is you would be fine-a $40-$60 job at a muffler shop.If you left the rest of the exhaust system alone the car would sound close to stock.the exhaust system is 3" under the car where the cats are at.That flows plenty for a stock motor.