e30 m3 s52 Exhuast Setup - Dual Pipes suggestions? ... yes i know...not single.

[r4esh]

Hey all,
I finished my swap (s52 e30 m3) but it wouldn't pass emissions. See my other thread here.

The right now setup is:
Aftermarket headers - not sure the brand. They are heat wrapped. -> DUEL 2'' piping -> Custom 2'' X-pipe with O2 sensor -> Duel 2'' pipes -> Stock OBD2 Cat -> Duel 2'' Pipes -> duel in duel out Aftermarket muffler - not sure on the brand.

Well I'm pretty convinced the Cats are the issue and I'm trying to decide the new route / idea for this dual pipes setup. Because I've already got it as dual pipes the whole way I kind of want to keep that setup.

So I need some good suggestions on which cats and resonators to use for this setup. Not too loud & little rasp. Everything I'm seeing seems to be for the single 3'' style setups most 24v swaps use. Ideas?

A buddy of mine recommended I get 2 of these: LINK
Or perhaps 2 of these.
^ But I'm not sure about "performance" and I don't want to blow too much money but I also don't want to "skimp out" on it.

Cheers!

[7pilot]

I used S52 primaries, custom secondaries (due to AKG engine mounts) into an S14 flange. Then VSR center section/Supersprint tail box.

No big job as the car will go back to S14 power in a year.

m

[r4esh]

I used S52 primaries, custom secondaries (due to AKG engine mounts) into an S14 flange. Then VSR center section/Supersprint tail box.

No big job as the car will go back to S14 power in a year.

m

VSR = pricey. Any other options?

[burkey001]

Put your o2 sensor closer to your cats. Put your cats closer to headers. Hotter=more bad stuff burnt up in cat

[burkey001]

Oh and it's "dual" unless your two exhaust pipes are adversaries with a score to settle. In this case duel on!

[r4esh]

Does it matter / make a difference if the resonator is before or after the cats?
I was thinking about his Resonator
and these Cats
But you suggested putting the cats closer to the headers, which makes sense, but with those resonators I don't know if I'll be able to achieve that unless they are AFTER the cats due to the size of them. Thoughts?

[Beej '86 325es]

Here's my setup. Since the collectors on my headers were 2", and since "track pipes" made by UUC and such are 2", I stuck with that the whole way back.

It's loud. I don't know that the resonators do much in the way of quieting down the exhaust. Since you're running cats, that will probably do a lot in that sense.

I don't think I would run an x-pipe. It may help for better O2 readings, but for power I don't think it will help, since on an inline-6 it works against the fluid dynamics principles that make it work on a V8. Someday I'll model this in our flow simulations software at work when I get some "spare time". :)

http://www.r3vlimited.com/board/showthread.php?t=209855&highlight=custom+exhaust

[burkey001]

Run nothing between your headers and your cats, except the O2 sensor(s).

Cats need to run as hot as possible to maximise their efficiency.

P.S - Does your motor have 1 or 2 O2 sensors?

[burkey001]

For emissions, put them as close as possible.

I have mine right at the front. Ground clearance does suffer however

[r4esh]

"burkey001" what cats are you running? what are those? / would you recommend them?

I'm running 1 o2 sensor since I'm OBD1. Thus the X-pipe / o2 combo. I was also informed that the X-pip or H-pipe helps mix the pips for a better sound.

[burkey001]

They are Magnaflow's race cats. 2.5in ID.
They sit quite low to the ground.

I transition up and down to 2.5in via some Burns Stainless transition cones. I don't know whether I'd do this again, it sure empties the primaries fast but the reduction in velocity makes it quite loud.

I think I'd get 2in ones, that will also fit better (smaller dia can)

I dont have them shown in the pic, but my two o2 sensors mount on the transition cone to the cat.

[r4esh]

I'm having trouble finding some good information on whats best. What is a better setup: 2 single cats? Or a dual in dual out cat setup? Here's what I'm NOW looking at:
Dual Cat : Cali legal or Cheaper / not cali legal
$50 in price difference is one going to be better performance wise? I don't mind spending the extra $50 with the prospect that one day the car may be in the hands of a California resident. Then there is running 2 single 2'' cats like THIS but that'll actually end up more expensive than the Cali Legal daul option above. I'm kinda lost looking at these and deciphering what is best / affordable.
For resonators everyone seems to use these on the single 2.5'' setups. Would 2 of them be overkill on my setup?
I'm hoping for someone's yay or nah so I can hurry up and get these ordered.... I'm missing my car right now.

[Jalves619]

I don't mind spending the extra $50 with the prospect that one day the car may be in the hands of a California resident.

Say what?

[scottinAZ]

I would go with the dual in/dual out, and use that as the X-pipe. Save the space for resonators or another noise reduction part.

Not that it really helps, but I run stock "I" dual exhaust off the headers on my M50. Keeps things fairly stock, and therefore simple. 1.75 pipes would probably be a bit on the small side for an S52, but the idea is sound.

[burkey001]

How does a dual-in dual-out anything guarantee those two pipes are going to cross over?
Would it not be wise to check such functionality would occur rather than just accepting it?