Another EX. Question

[TSIDrummer]

I am considering getting a 3” turbo back exhaust with an O2 eliminator down pipe with the wastegate pipe venting to the atmosphere and no cat. What are the pros/cons of this setup other than the obvious emissions issues?

[hoffman]

Pros: Little restriction to gas flow
Increased turbo response

Cons: Eliminator DP can be a hastle when doing a turbo swap
Increase in boost spikes/creep on small turbos

If you can get an 02 eliminator that is seperate from the DP it may be worth you while. Unless that is what your looking at and I'm not understanding your statement.

[Hal]

There are no emissions issues.

Put a cat on it and with a proper tune, you can pass with virtually any size exhaust.

[TSIDrummer]

Hmm...ok. So with a high flow cat, does that make eliminating the O2 the way to go?

[hoffman]

The 02 is a completely different part of the exhaust system.

Turbo->02 housing/02 eliminator->Down pipe-> Cat/test pipe-> Muffler.

The 02 elim. provides a passage to atmosphere for the WG passage. Even if you had to run emmission the WG shouldn't even open anyway since the turbo won't be boosting.

The Cat. is a restriction. High flow or not. If you don't need, save the $150.

[TSIDrummer]

Yeah, i was saying that in the manner of emissions, if i just have a high flow cat, i can go with the O2 eliminator, and that would give me more flow than otherwise.

[Mirage]

I don't think you're getting the point. Getting an O2 eliminater has nothing to do with the cat. Flow or otherwise.

How about doing this:

Get a true 3" O2 housing with at least a 38mm external wastegate (routed back in or externally dumped to your preference). This alone will take care of the wastegate passage, boost control, and any creep or dropoff issues.

Have a 3" mandrel bent downpipe made (or make a downpipe) that mates to the O2 housing and has provisions (flanges) for a cat if you're worried about emissions. If you don't want to ever install a cat, simply make the downpipe long enough to mate up with the catback.

From there, mate it up using flanges to your existing 3" catback (backhalf).

This will pretty much guarentee that you won't have any boost control issues (barring the controller and lack of porting) up to at least a 50trim turbo

Externally dumping your wastegate will NOT have an effect on emissions as long at they (the test station employees) don't hit full boost. The wastegate should stay sealed until close to the target boost pressure.

Having the cat in place will allow you to pass the visual inspection, but does not mean that you can't pass without one. You just simply have to retune a little to make a complete burn.

Marcus

[TSIDrummer]

Oh, ok, thank you for clarifying that for me. I really wasn't getting the whole picture.

[hoffman]

I suck at painting pictures, but atleast you got it.

[TheJackal]

There are no emissions issues.

Put a cat on it and with a proper tune, you can pass with virtually any size exhaust.

Hes in brighton, weld country doesnt have emissions..

[TSIDrummer]

Actually, I'm not "in" Brighton, or Thornton, It's Unincorporated Adams County, so yeah, i still do have emissions...don't have to take another test for another 2 years tho ;)

[TSIDrummer]

That being said, is there any way possible that it would pass emissions without a cat if it was tuned well enough?

[DSM16GSX]

It is perfectly possible to pass emissions without a cat, unless the person inspecting your car finds that you don't have a cat. If you were to gut out a 3" cat so it looked as if a properly working cat were installed, but it is really hollow, you may still be able to pass emmissions if the car is running/ tuned well otherwise. Basically, the cat only needs to pass a visual inspection and will probably not effect the probe readings to the point of failing the test. My 3" exhaust system is all 1 long pipe with no cat and a muffler at the end. I just take off the 3" exhaust and hang up a stock exhaust system for emissions time. It really isn't hard to swap out an entire exhaust system, it can be done in probably 30 minutes or less.

Alex
91 GSX