There are Carsound Magnaflow, Eastern, and a few other brands of $50 highflow universal cats on ebay. I'm looking for something better than stock that I can weld in place. Have any of you used one of these?

 

Unless the manufacturers can supply flow numbers, there is no way of telling how good or bad the cats are. If price is any indication of quality, $50 doesn’t buy much. You may drop them a note and ask for some flow specs (the pressure should be on the spec sheet).



Random Technology makes a bolt on three inch cat that flows over 500 CFM at 28 inches of water. If you could somehow get 95 percent VE out of an NA, that cat would still outflow the engine by over forty percent. I paid $260 plus shipping for mine, which is a tad bit more than the ebay vendors. The good news is, I 've seen them for less than I paid.

 

the stock cat is better in, durability, and ability to clean the exhaust than anything else.



carsound seems to be good, we ordered the biggest one for my car, its still not the same size as the stock main cat

 

I had a Dynomax (I think) cat for a few years (3", $140 from Jeg's or

summit). Replaced it with a Random (~$240), which looks exactly the same inside.

Random used to use a lower cell density with heavier washcoats to compensate

but apparently don't anymore (400 cell / sq in like everybody else)

Both of these cats flowed the same as far as I can tell.



I see that Jeg's now sells metal substrate cats. The downside is there's

no air tube, so you'd have to improvise a little. Note that AFAIK, metal

substrate cats are not universally EPA approved - only specific

applications that had them as original equipment such as Porsche.

 

I hate to sound like a newbie here, but this area is not one that I have experience in. Do highflow cats actually give u power like a header or are they pointless noise adders? Installing my header dropped my quarter mile time from 15.6 to 14.9. Would the better cats have a similar effect?

 

If your current cat is damaged (melted, or like one I had where the brick had come loose and fallen on its face), you'll get a good increase.

If your old cat was a pellet type (it's not), there would be a big improvement.

As far as some of the claims of flow rates, I'm skeptical for this reason: when I put a converter (3" high flow) on my car, boost response dropped by 2 psi at 3000 RPM. Without a cat, I couldn't measure any real pressure downstream of the turbine. With the cat, I've seen 4-5 psi. This goes for Dynomax and a fairly new Random (I believe Random used to have a better flowing cell density but they no longer do).

Metal substrate cats are becoming available - these use corrugated stainless as the substrate. Stainless can be made thinner than ceramic, so there is more open area for a given cell density (<--key point). Also the metal core heats quicker, withstand higher temps, and doesn't crack. However, I haven't personally tried one yet.

 

i think you will notice a difference, maybe not as big as the header though.



between the cat that we put on the 3 rotor and the stock fc cat the big difference was the 3" in and out. the brick also was a little less fine on the aftermarket one

 

i made my own cats for everything i've ever owned. find an old cat, cut the flanged off the ends and go to the local parts house- find some exhaust tubing thats the size you want, measure, cut and weld. i dont think you'll beat the price and if you do it right, it will be just as durable, if not more than anything you'll buy. then again, thats really not a cat, its a test pipe but it makes power and it met my needs. may not be legal which is why i chopped an extra one.

 

Thanks guys. I want at least some kind of real cat so the car won't stink and to keep the noise level down some. My stock cat has a crack in the lattice and also has a big, flat plate with holes drilled in it welded a couple inches behind the inlet pipe. I can still see through the lattice (barely) when I hold it up to a light source, but the stock fc cat is the longest cat I've ever seen on a car this size.



If I could lose .3 seconds in the 1/4 by changing out this old cat, I would be stoked. That is roughly half of the effect that installing the header had.

 

actually we have had 2 cars that are unbelievably slow, that have turned out to be bad main cats