View Full Version : high flow cats vs. no cats

07-18-2003, 10:32 AM
I currently don't have catilytic converters on my car.

I have long tube headers with 2.5" collectors into 2.25" pipes that go to one 3" pipe and then back to two turbo mufflers.

If I put a set of 2.5" catco cats after my headers will I be sacrificing performance?

I've heard that high flow catilytic converters will not create significant backpressure to hurt performance. I've also heard that 02 sensors work better with cats.

Do catylitic converters make a significant reduction in pollution or are they as useless as other emission control features on cars?

Basically I'd like to do my part in keeping the air clean while complying with Federal Law but I'd like to know if and how much HP I'd be sacrificing.

Any factually based opinion on catilyt

07-18-2003, 04:14 PM
My car has no air pump or "smog pump". Isn't there a tube that injects air into the catilytic converter to help the burn process?
If I don't have an air pump and I put cats on, are they even gonna work?

I've been told that a properly tuned car will pass emission testing without any catilytic converters. Is that true?

There's no testing in Michigan and very few tuners and hot rodders have catilytic converters. I'm not gonna put them on if they don't prevent pollution even if they don't hurt performance.

Any opinions??? comments?

David Neibert
07-18-2003, 05:36 PM

My exhaust sounds similar to yours except I have Kooks medium length headers, 2.5" downtubes and high flow cats. I don't think the cats are hurting my performance.

The cats work by heat from the exhaust. No air hoses or anything else is required.


Rob Noth
07-18-2003, 05:40 PM
Cats do prevent pollution. All cars, no matter how well tuned create CO, NO/NO2, and VOC's. That stuff is what leads to smog, acid rain, etc. Cats reduce or eliminate these from your exhaust.

Even though a well tuned car without cats can probably meet the limits in a smog test scenario, running closed loop at stoichiometric ratio, that is not very "real life". With an SC, it's much more likely to be at WOT! And then it's running real rich and spewing lots of junk out the exhaust.

07-19-2003, 11:59 AM
Thanks for the input. I guess I'll wait to hook up my exhaust to my headers until I get the cats.

I do enjoy clean air.