Misconceptions.......
... and don't forget the air we all breath.
yeah, that is what I was thinking too.....but I hate to delete all the cats! from what I read on here most done reccomend that due to a substantial loss in back pressure.
i agree with the cats but dont delete them replace them
OK, 1st this site's hostility to removal of cats, due to legal issues is, at best, hypocritical. I don't really want to start this discussion just yet, as I don't have time to do so properly right now. But, it does need to be addressd and discussed at a future date. For now, I'll just say this: Many of the mods who have killed cat removal threads, themselves have substantial mods on thier own profiles/vehicles which are just as technically illegal as removing the cats. This is just one of many points on this issue. I do intend to start a seperate thread for just such a discussion/debate at a later time.
2nd, there is a HUGE misconception that "our" motors, "need" backpressure. NO motor EVER NEEDS backpressure. What they do need is adequate exhaust gas flow velocity. Using grossly oversized, or poorly designed exhaust systems can substanstially reduce power output, in one of two ways. One is killing flow velocity, and the attendant scavenging effects. The second is excessive backpressure, due to pipes which are too small, have too many bends, or other restrictions in the system (such as CATS). While OEM cats have improved significantly in the last couple of decades, they are still, and always will be, a restiction which hurts performance. Ofcourse, that statement requires a bit of qualification. Simply "gutting" your cats is bad. It creates a big open chamber, and almost always creates weird flow patterns that reduce flow velocity and scavenging, and hence reduces performance. However, removing the cat, and replacing it with a properly sized lenght of straight pipe will almost always improve performance,by increasing volumetric effeciency of the engine ( just a big air pump: more out=more can get in=better performance), especially if it accompanied by supporting mods.
As for Al's comment regarding air quality, it is quite possible that a vehicle w/o cats could be tuned such that it actually produces lower emmissions than it had in stock form. I certainly don't want to pick a fight with Aldive, as he is a well respected member here, and he has a lot of great ideas and opinions, but we're right back to the whole hypocrit thing mentioned above. How? Well, several of the mods al has done and spoken of here are just as much a violation of the clean air act as removing the cats. Take the "custom" tuning for example; I doubt his Ex has been submitted to the EPA for emmissions recertification. I also suspect that, even with his cats in place, his tuning mods probably result in higher tailpipe emmissions, at least in certain categories. I would guess Nox, for one. Why? Well, to get the kind of mileage he claims (and I don't dispute), one would have to run leaner than stoich at cruise, and certainly less power enrichment. Leaner equals hotter exhaust which tends to increase Nox emmissions, though it probably lowers unburnt hydrocarbons. Of course this is academic, as even if these mods resulted in pure oxygen and bubblegum coming out of the tailpipe, they are still illegal tampering.
You can either cower in fear, and do what the jackbooted thugs of the government want, or do what you believe is best for YOU and YOUR vehicle.
So...... to the original poster, my advice is this: If it is in fact your cats, and you already have or wish to buy an xcal,etc... w/ custom tuning, then cut them out, replace it with straight pipe (disguised w/ the heat shields from the old cats), have your rear o2's and the associated trouble codes disabled in the tunes and motor along your happy way. (it should pass both visual and the computer portion your inspection process, provided they just plug into the computer,as they do here.) Buying a tuner is cheaper then replacing them, and you'll have better performance.
Or not.......... It's up to you
America... Land of the Free?????????