Catalytic Converter question


Oct 28, 2003
I am currently running a Hooker Aerochamber dual exhaust system with a test pipe. I am tired of the exhaust drone and the fumes are driving my wife nuts so I am thinking of putting a converter under it to fix these problems. The question is what are you guys running and what would the drawbacks be of running a converter on these cars?
Ive run into the same problem, I get " i don't like this car, it stinks" , so i made this nice little system up, and the car does feel a bit slower, but it should still go 10s i hope. These are random cats 4" outside diameter, 3" inside, flow 580 cfm im told each, so i decided to put two on to double the cfm. ANy generic hi-flow cat is not going to flow over 450 cfm, and can't endure high temperatures becuase of the ceramic mat'l breaking down, so you need the metallic matrix material inside. These cats go for 250 a piece, but if you want to lose a bit more hp go with the regular cat, but you will lose more hp for sure.

check out the pic on my car
If you want your cat to live, make sure your engine isn't misfiring or that HC is not excessive. It isn't the heat the breaks the substrate (ceramic) material, it's misfires. When your engine misfires, it pulses against the substrate material and cracks it. Yes heat is a contributing factor, but the misfire pulses creates the problem. Excessive HC causes the cat to excessively react and will basically cause an internal meltdown (eventually plugging the cat). I suspect most high flow cats work pretty well, the more expensive units have more noble metals (platinum and/or paladium-used to in the oxidation section of the cat and rhodium-used in the reduction section of the cat). So a cheaper unit will sacrifice the elements that the cat uses to reduce emissions. Stay away from the pellet style cats (old GM flat style) as these are too restrictive.
How is a converter going to help the fumes?

I'm not sure slapping a cat on a car that pukes lots of fumes is a viable solution.

On the other hand, slapping a cat is cool...

Originally posted by strikeeagle
How is a converter going to help the fumes?

I'm not sure slapping a cat on a car that pukes lots of fumes is a viable solution.

On the other hand, slapping a cat is cool...


That is a very accurate statement (esp the part about slapping a cat:D ).

A catalytic converter is not the catch all, cure all. A properly tuned engine will go a long way in reducing obnoxious fumes. The cat will clean (the emissions) it further.
no no no no all wrong never put a cat on these cars way to damn restrictive they suck, only slow cars have cats " in my opinon" i say if she says "i dont like these fumes" you say "take a walk ":D
i hate cats i have a dumper on mine and i dont get crazy fumes i mean a lil yes but nothing to wear you cant stand it. check the tunning of you motor might be running to rich.
Does the test pipe slip over the DP? I know on THDPs it does. It's supposed to, to minimize the mechanical loads the exhaust system imposes on the turbo.

If it does so on the Hooker set-up, maybe there's too much gap there? I'm not saying there is, or what to do about it. Just speculating that that may be your "leak"?

Where do you suppose the fumes are coming from? Certainly not from the lack of a cat, I hope?


I recently put on a new 3" cat from Ramchargers for my THDP, and I was very impressed that I didn't lose any boost at all compared to a test pipe. Was 23 psi in 3rd gear with and without the cat, on a 12.20ish car without the cat on 93 unleaded. No time slips with the cat but it felt about the same for what that's worth :). Apparently this is only a two-way cat, though, not a three-way that also handles NOx.
cats suck, but ill just take them off at the track, since i have a nice flange set up, that i can take them off in about 30 seconds, anyone interersted i can get more and send them to you, sizes are 2" , 2.5" 3" and 4" stainless steel, and a reuseable copper oring seal anyone can make. I'll have to check the current price if anyone is insterested.