I just bought a new cat for my S5 GXL, but there is no flange on it for the air pipe. I guess I'm gonna cut the flange off the old one and put it on the new one, but there is a small problem.

I don't have access to a welder. How can I attach the flange. I was considering JB WELD, but I don't know if its a good idea with all the heat involved in that area. Can anyone tell me if it's a good/bad idea to JB WELD it?
Thanks.

 

I would vote a definate NO on the JB weld idea.. Dont get me wrong..I absolutely love JB weld..and use it all the time, butI dont see it holding up all that well down there.

Where did you buy the cat from? Is it a rotary specific cat? Our cars generate alot more heat and much stronger exhaust pulses than a piston engine...and will most likely destoy/melt a "universal" cat in a matter of weeks/days.

 

Be sure that the cat you're getting is rated for the EXTREME exhaust temps that the rotaryproduces. That said, when I installed my Bonez cat it didn't have a flange so I cut the flange off the air pipe and attached it with a short piece of silicone hose. Works like a charm!

 

I'm not sure if its "universal." I talked to the guy at the auto parts store (a good one I frequent, not Kragen's) and told him I needed an RX-7 cat that was as cheap as possible. The brand is Perfection and it fits right and came with flanges already on it. But the air pipe into the cat is just capped off.

I'm kind of confused here.
JB WELD will NOT hold up, but a piece of silicon hose will?

 

Generally speaking most modern cats are all about the same - muffler shop cats will work just fine, they used to on my car...emissions testing after a tune up and a fresh muffler shop cat and my FC was putting out ZERO HC's That motor was miiiiiiiiiint hehe

 

No they are not, lesser cats will fail alot sooner than those made for rotaries - first hand experience and expense $$

 

sorry--wrong thread delete

 

Anyone have anything to contribute in the JB WELD vs. silicon hose debate?

 

Do you really need the check valve to pass emissons? Has anyone tried without it installed? I don't think that it'd really melt your cat if you didn't have that on (no more than normal rotary exhaust at least).

 

Get a 1/2 inch brass compression fitting used to connect copper tubing. Got mine at home depot (in the plumbing section) for about $3.00. Works great no leaks. Has not melted yet.

 

if you want exhaust leak heaven then id definitly go for the JB weld. My friend melted off the JB weld on his 240sx in a couple of days, i cant even imagine how quick it would melt on our racecars mr gadget is right. Cats from the muffler shop almost always have material wrapped around the actual converter that cant stand the heats of our motors. It burns up, the cat element wrattles around, clogs and causes more trouble. if i were u i would look for somebody that will weld it for you. throwin in my .02 cents -alex

 

cut the flange off the air hose and connect the split air pipe to the air inlet on the cat w/ heater hose. I would also recommend two hose clamps on either end of the heater hose. A high revving engine tends to blow the hose off the cat without clamps.

 

I've been using my silicon hose connection for about 1000 mi now and it's still working great w/no leaks. I'll update if it ever fails...

 

You need the check valve to stop exhaust from flowing up into the ACV and making your car sound like a tractor.

 

duct tape. or if you know a place nearby just ask them to weld it. it shouldnt cost that much

 

Welding a flange on would of course be the best way to fix it. That's what I'll do if my hose burns through.

 

oh I know that NZ but I mean, do you need that pipe there in the first place to pass emissions. Are there cats that can make us pass without air being pushed into them?

 

Your cat needs fresh air to do its job. The HC count on my GXL went from around 1000-1200ppm to 2ppm when I got the ACV working right. (Legal limit in CA is 150ppm)

 

There are cats that do not need air injection, but I'm not sure if they gaurantee a pass. Depends on how strict the test is.