Anyone recommend a particular brand of high flow CAT that won't add back pressure to a full length 3-1/2" SINGLE exhaust system ?
12 PSI over 5.3L, nothing crazy- maybe 500 Wheel HP.
IS it possible to tame the exhaust smell without LOSING Power ?

 

Everything is a trade off. I'd get any 200 cell metallic cat based on what I have seen in aftermarket turbo back exhausts.

You can also find 100 cell cats, which will have less flow restriction but I can't say if that will be enough to kill the smell.

 

3-1/2 " seems to be a difficult in-between size.
3 inch all over the place, some 4" parts.
Who's selling a good stainless 3.5" CAT.
Also: How far from Turbo does CAT need to be to survive ?

 

Look at OEM mfgs, they put the cat immediately after the turbo.

3.5" inlet/outlet is literally everywhere, do a search on summit's site

 

I am running a 200 cell cats on mine. If you put the cat too far away it won’t work.

 

Nose plugs. I didn't realize this forum had become Weenie Hut Jrs.

 

It still smells soooo good unless I’m running white lighting then it has zero odor. Ha

 

A 3.5 inch cat will kill power. Look into a 4 inch or 5 inch cat, it will flow much more air. The new 3L single turbo BMW cars have a 5 inch cat right off the turbo, they are only rated around 450hp if I remember correctly. I would place yours back a few feet as the cat you're using will likely not be of OEM quality.

 

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Thanks for the tip(s)
Recommend source for such a CAT ( Yeah, I expect Chineese, it's okay don't need to pass inspections)

Also, any downside to what would appear to be a BIG BUBBLE in middle of 3.5" pipe ? I've seen 4 stroke motocross header pipes with the " Power Bomb" expansion section, always wondered how that works. LOOKS like an Impedance Bump.

 

After building 3 LS turbo cars, here is what I have learned about exhaust smells.

People are always quick to remove cats on a turbo build (myself included) for the sake of making power and spooling quick.

Once you add an aftermarket cam that has increased overlap, you will get a stronger smell especially once the cats are gone. Maybe I'm just getting old but my tolerance for stinking like exhaust after going for a drive is going down fast.

The obvious solution is to add a cat back in and make sure the exhaust is full length, terminating at the rear of the car in the airstream (preferably not a low pressure zone) to help dilute it. The OEMs run cats as close as possible to the turbine discharge so that the cat is able to "light off" quickly for emissions purposes. They are restrictive, which is why you can realize such good gains by going with a catless downpipe (look at the turbo BMW N54/N55 guys).

To truly have the best of both worlds, install a pneumatic cutout as far upstream as possible (pre cat) to allow the turbo to spool quick and remove restriction when in boost. I have used a boost activated one with great success - fully automatic, normally closed with spring pressure, triggered by boost via simple rubber hose from intake manifold.

I am interested in trying the same setup with a vacuum actuated cutout (normally open, pulled shut by vacuum). This would give a bit of a bark on startup but quickly close.