Im still searching for a cat that can actually flow enough not to be restrictive. I have a catco 3", but that holds the car back. Its basically just a regular ol' cat with 3" flanges on it, so its not much of a surprise.

Would be nice to run one so the car doesnt stink all the time. The engine and tune are currently set up to utilize a cat, but I cant find one large enough. Are there any trucks that have a large one that could be adapted? Maybe gang two of them together? Not sure if I have enough space under the car.

 

This is exactly what I'm just finding out ! The "high flow" catco cat only flows 299 cfm according to this web site, http://www.smb.net.au/catalyticconverters.htm
They offer a 4" metal substrate ? converter that flows a little better, but this web site is designed for imports. The accepted math is 2.2 CFM per HP for a motor to perform well on the exhaust side. So if you have a 300 hp motor you'd need 660 cfm of exhaust pipe flow. A 3" pipe flows better than that but not with a catco cat. I'm thinking of maybe adding a second high flow cat in parallel to the one I already have. 600 cfm is better than 300?

 

I was thinking of maybe putting two side by side. Its hard to get enough space for them with a single 3" i-pipe. Have to split the pipe to the two cats, and merge it back together again.

I can say that the catco cat is like a cork. I measured the backpressure on my old engine, which only put out like 250 HP, and it was close to 10 psi at 5k. Way too much.

I remember seeing an old truck tv episode with an EFI S-10 V8 swap. They managed to get teh biggest damn cat Ive ever seen for it. Was about 3x the size of a normal cat. How come nobody makes them like that? Too much heat loss? All the cats are always tiny as hell.

 

No it doesn't, find out where the true restriction is - its not in the cat. Maybe its overall exhaust diameter. If STOCK LS1 cats can support 500 horsepower, I highly doubt that Catco (which is usually classified as high-flow) is choking yours. Flame suit on.

 

LS1 camaros have two cats, both of which flow around 400 CFM or so. There really isnt a restriction in my exhaust, other than maybe that it should be 3.5" instead of 3". Both the resonator (dynomax bullet) and the muffler (which is basically just a perferated 3" tube) are fully open. The cat itself is a restriction, which is why I normally dont run it. Really, I should be using two instead of just one. The catco would be good enough for something like a 3.4L, but not enough for a 350.

 

I'm using the following on my 350HO Deluxe (I've never felt that there's a restriction): Hooker 2055's, Catco 9118, and Hooker catback.

JamesC

 

Thats basically what I have, except that theres a straight pipe in place of the cat (catco 9118 as well, currently in its box). Subjectively, I always found it kinda hard to tell how restrictive it was without actually measuring the backpressure. I suppose that in the long run it may only suck 20-30 HP at WOT, but its still kind of annoying to have something skimming power off the top needlessly.

 

What about the Random Technology Cat.? They claim to have the highest flowing cats on the market.

 

I was looking at them. They claim flowrates up to 600 CFM as 28 in. of water. Thats about 2x the flow of the current one I have. Expensive, though. What I would like to ultimately do, is mod the y-pipe to allow two cats like the TPI cars. That and some random techs would probably be as free flowing as your ever going to get.

 

Might help.....
http://www.installuniversity.com/ins...n11.122001.htm

 

Random Tech. claims that the 7000 series SuperStainless catalytic converter flows 617 cfm.
http://www.randomtechnology.com/

Tests.....
http://www.randomtechnology.com/tests.html

 

Maybe one of the new diesel converters? dont most diesel's have 4 inch exhaust from factory?

 

the random tech cats work very well. especially when looking for the extra tenths needed to win. i have used them. although rather expensive they are a really nice piece.

 

i have heard good things about magnaflow spun cats, they are very compact as well

 

The "low" of the high flow is how they work or get hot enough to work, the exhaust heat alone isn't enough if it just blow through like nothing was there plus it give some extra "time" to burn off gasses right???

If you could get a self heating element inside, that could glow red hot and allow full flow, and still burn off gasses....... = profit when everyone else wants one too.

[ a cat that can flow like an open pipe but still clean the "air"]

 

Its true that there is a min ammount of flowrate needed for the cat to stay warm enough to work. Most cars today have two cats, anyway, due to how restrictive they are. Also keep in mind that GM used dual cats at one point as well on 3rd gens. I could see this being an issue if you tried to use like four of them or something rediculous, but they should work ok with two as its basically like each cat is hooked to a large displacement 4-cyl.

 

Magnaflow spun cats 3" Version flows 596 CFM and they are relatively small.

 

Years ago I seen a cat a guy had. I think he said it came off a Corvette. It had a wide oval mouth. It would take a little work making a flang to bolt to it and fit over the wide opening. This was like back in the mid to early 90's.
Also I had stumbled on the dual cat set up that is found on the later HO third gens. But I remember it being somewhat expensive. It was complete Y pipes to converters to a single outlet. I found a guy on craigs selling this pipe along with some rusted headers. I asked how much for just the cat set up. He said call and he would give me a great deal. The guy was also selling some KYB struts for $150. If that is what he considers a deal he can screw himself!

 

The magnaflow looks good for its size. It would be easier to squeeze two of those together in the limited space under the car.

 

This would require adapters, but this Magnaflow 3.5" spun cat may be what you are looking for. It takes up little space as well.

http://www.summitracing.com/parts/MPE-59920/