I'm considering removing my CAT temporarily before replacing it with a new one, but will be driving for a period of time without the CAT. I've read all sorts of instructions of how to remove it, but nobody specifies if it HAS to be replaced with a straight pipe, or if I can simply drive with it removed (as in an empty space gap in the exhaust where the cat used to be). Can someone give me a straight answer? Is it ok to drive with the CAT just "gone" or does it have to be replaced by something?

I've heard I can hollow out the CAT, and put it back in its place, but I'd rather not do that if I could just leave nothing in its place.

Any info is appreciated, thank you.

 

The catalytic converter is used to help control pollution that is released by the turbo. What it does is take the polluted gas and turn it into less harmful gas via chemical reaction. It is also used to burn off any un-used fuel, so you might see flames coming out of the tail pipe. What will also happen is that the exaust will smell like rotten eggs. So, all I can say is that you better hope that a tree hugger or a cop doesn't drive behind you. Cops tend to get a little upset when they see flames coming from the back of the tail pipe.

 

You need to at least replace it with a straight pipe. If you don't, your car will be extremely loud and you will have flames coming out underneath the car. Something I try to aviod. Also, if your car has the oxygen sensor screwed into the cat, you need to find a new home for it. Otherwise your engine will be running in open loop mode and dumping all kinds of fuel in causing more unburnt fuel into the exhaust. You'll end up with a flame thrower. Of course it would kill your gas mileage as well.

 

what act1292 said.

p.s. 91-740turbo.... a 1984 240 doesn't have a turbo, but if you replace 'turbo' with 'engine', your statement is essentially correct.

ever heard a harley with no muffler? no, not that obnoxiously loud one down the street, he probably has a muffler, just a really limited one. no muffler at all, sounds absolutely hellacious. your 240 will sound like 2 of them. without a 'test pipe' in place of the cat (or a new cat), the exhaust gasses won't make it through the mufflers, they'll just blow right out the end of the headers?

 

Thanks so much for the input. I was about to just cut that thing off.
So I looked at the cat and it's welded into the exhaust system.. I would have to saw it out, and I don't have a blow torch to weld on a test pipe. Do you guys have any idea if a mechanic would do this for me? I dont know how else I'd install a test pipe, can it be attached to a sawed exhaust without a torch? How expensive would this be, cause I can't even afford a new cat right now.

 

why are you doing this?

volvo factory cat lasts for about 400K miles if the car is kept in halfway decent running condition.

no legit licensed mechanic or muffler shop in a smog controlled state would install a 'test pipe' in place of a cat.

 

I have a feeling it's not the factory cat, by the way it's welded into the exhaust and has no bolts. I brought my car to a mechanic and they think the cat is bad and resulting in poor fuel economy, among other symptoms. I'm about to drive from Houston to New York and I really need a few extra MPG. It makes a huge difference over 1,700 miles. So I was really hoping for a cheap temporary fix, I could install a test pipe, then hopefully afford a new cat before registering and inspecting my car in NY. Since there are no bolts involved in my cat, I don't know that those test pipe kits will work for me, or what the situation is with installing those. I'm very strapped for cash, trying to keep enough to make it back to NY.

 

afaik, most cats are welded in place, not bolted.

a cat would have to be REALLY clogged up to create excessive back pressure to cause those symptoms. long before that it would fail emission tests with excess CO etc.

I'd imagine you could check the flow by removing the O2 sensor (to let air in), and putting a shop-vac on the exhaust pipe... if the vac has to struggle to pull air through, maybe you have a problem.

 

Ok I'll try checking it. Thanks for all the info you've all been a big help, especially you pierce, you answered all my threads/posts.