would that work? if you get those small metal substrate cats could two be welded onto a midpipe? so the exhaust is cleaned twice? reason i am asking is because i am wondering it this will help a super modified fd pass smog....so this wouldn't be on the car any longer than going to/back smog shop. i know it sounds stupid but i know nothing about exhaust/smog.

 

Has anyone put two res midpipes to quiet their car down a little?

 

jus get the pre cat and main cat...

 

Your answer is yes. Two cats in series will not make it twice as clean, but it should be an improvement over one. There are many factors; however, you'll need to keep enough heat (and free O2) in the exhaust for the 2nd converter to work well. Put them as close as possible and wrap the pipe in front of them (downpipe) and any space between them. They don't have to be metallic either--ceramic cats clean just as well. If you do a metallic-->ceramic combo, you will essentially have the factory precat/maincat conversion setup.

 

why not just get a cat +muffler setup like alot of people? either get a borla xr-1 with a cat or a magnaflow muffer with a cat

 

tuning plays a big part in passing emissions not just the presence of a cat. lots of people have passed on one main cat with correct tuning. also depends on your mods. porting makes it harder to pass smog.

 

Why bother? Just throw a stock or hi-flow cat on for testing. It takes a leisurely 20 minutes to jack the car up and swap out the midpipe for a cat. You'll need an air pump hooked up to pass anyway.

 

i passed with flying colors with a ported motor... bought an electric air pump out of a corvette and wired it up, plummed it to my high flow cat... and viola... passed no problem.