Sorry for the newbie question but what is a cat back or decat?? Not sure if thats how you spell it. I keep hearing that online but not sure what it does and what it is. I use to buy exaust for my bimmer and all I know is that they call it rear muffler or full exaust. BTW what kind of exaust do I need to get for the Evo 8 in order for me to get good performance but keep the sound level minimal. Thanks

 

A "cat-back" replaces the portion of the exhaust from the tailpipe to where it reaches the catalytic converter. Similarly, an "axle-back" replaces from the tailpipe to the flange that is found near the rear axle. A "turbo-back" is a bit of a misnomer as it replaces from the tailpipe to the O2 housing and doesn't always involve removing/replacing the catalytic converter. A "true" turbo-back exhaust would also replace the O2 housing (causing the conventional "turbo-back" to be renamed as an "O2 housing-back," but that just doesn't flow off the tongue well ). A "de-cat" is basically removing the catalytic converter and replacing it with a straight pipe (*for off-road use only). The following diagram should help explain.

Check out this page to get an idea of sound levels/quality: http://www.norcalevo.net/forums/modu...view_album.php

 

Thanks for the info and link. So what type of exaust will give me the best performance? I know straight pipes are just too dam loud and you mentioned for off road use only, why is that?

 

Actually I run straight piped in my evo and it's not too bad. I'll get a vid of it

 

i have a straight pipe and its not that loud. never got pulled over, but it does smell pretty bad

 

straight pipe has the best performance? Why are they used for off road only?

 

Straight pipe has the best performance because is has the least restrictive flow. Its for off road use only because its illegal on regular roads. Without the catalytic converter, the car does not meet emissions standards.

 

If you have the coinage the Vishnu dump-back with a 3" downpipe gives good performance improvements with a good sound thats not to loud but has a nice growl to it. (dump-back is Vishnu's "step up" (quality, hp gains) from there standard turbo-back).

I put one on last week, and love the sound everytime I fire up the beast ...

 

We are almost finished with our prototype mold for our cast (like factory) O2 sensor housing which incorporates a 3.0" outlet to match our new Ceramic coated 3.0" downpipe which will complete our "Turbo-back."

Also soon to be released is the WORKS heat-shielded High-flow cat and resonated test-pipe as part of our WORKS Racing Program.