Since I live in an emission control area (the test station is only a short run from my apartment) and I want good exhaus flow, I had an idea.

What do you think of running a dual outlet header to parallel cats and keeping the whole system separate from the engine to rear bumper? Throw some high-flow mufflers at the loud end and the gains should approximate that of running stock exhaust with gutted cats.

I know some have said it sound terrible, but sound is really my last concern.

 

Should give you a nice performance increase.

And I must commend you on your desire to keep the stock emissions working!

 

Though you may pass a snifer test like that i don't think you will pass a visual inspection. Headers are not legal even with a Cat in most emmisions areas (at least California) plus how do you plumb the smog pump? without the clean air of the smog pump flowing in both cats one will read WAy above the one that is not plumbed to the CAT, thus failing you.


-Robert

 

i was thinking about this for a while, i even asked about it in a thread

https://www.rx7club.com/showthread.p...ght=true+duals

that has some ideas and good discussion if you want to read through it

 

I had the Rb road race headers and 1 cat on each pipe, and some spintech mufflers and it was loud as hell, it got really annoying after awhile. The power increase was very noticable but it was way too loud for my taste

 

Not all aftermarket cats require air injection. Like you said, it won't pass visual if that's required, but it may well pass the sniffer depending on the strictness of the test.

To be honest, I'm not sure how much difference the air injection makes with aftermarket cats. Most of my knowledge on this comes from the Aussies (we don't have testing), and if you have a well tuned engine with an aftermarket cat (no air injection) then you'll generally pass the sniffer. Maybe air injection cats are cleaner, maybe US regs are tighter than Aussie's, maybe both.

 

I am just going based on what I have read in the west section. Nobody can seem to pass without the air injection, most guys are hooking up corvette electric smog pumps via a on/off switch in order to pass the snifer. It may not be as strict in WA, but thats what it seems the CA guys are having to do... some have to do that and add denatured alchohol with a cat to pass.. .. very very high standards in CAlifornia, we cannot smog at idle we have to smog on a dyno at 15 and 25 MPH with the wheels spinning.


-Robert