Hi all. I am seeking for opinions for an exhaust setup. I sat in my buddy's 3G the other day, and he has the following exhaust setup:

1) Pre-cat deletes
2) ATLP J-Pipe
3) 3rd cat delete, not sure whether he has the RV6 or ATLP straight pipe
4) ATLP base exhaust

In general, the car sounded pretty good. But the noise level gets pretty harsh at higher RPM and the smell wasn't too plesant. I am working on purchasing a used supercharger for a decent price, and wanted to go down a similar path as far as the exhaust goes.

I have learned that no cats will be the optimum setup for the supercharger. Like I said above, I am not liking the smell and the noise, so the following is what I have in mind:

PCD -> ATLP or RV6 JPIPE -> ATLP or RV6 HiFlow 3rd cat -> ATLP or XLR8 exhaust (with some sort of resonator in between to cut down the noise).

Now here is the question for the gurus: With the setup above, will a Hi-Flow 3rd cat deteriorate performance/exhaust flow for supercharger??? ATLP's site talked about their hi-flow 3rd cat consists of 200 cells vs. 900 stock (I think), and I can't get any info on RV6's 3rd cat.

Inputs/options/comments please!!

 

No a hi flow 3rd cat will be fine. It may take a hp or two of power but you will never notice. If you don't like the smell and raspyness get hi flow primary cats, they will get rid of both.

 

there are hi-flow primary cats? who makes those?

 

i thought i remember reading that adding boost to a completely free flowing exhaust isnt good...i will look for proof. something about needing that added back pressure that the cats provide...

 

and i always thought boost with a free flowing exhaust is good.

 

You want the best flowing exhaust for FI applications. Turbos moreso that superchargers because a restriction downstream can hurt spool.

There are no worries about loss of low end torque. The turbo or blower more than make up for it.

 

Would it be BAD to drill extra bigger holes in the stock catalytic converter on both ends hence more flow? There's NO O2 sensor plugged in so no check engine lights etc.?

 

If you're going that far, might as well gut it completely like I did. No worries about check engine light.

 

Thanks guys for your replies!!

I hate cars: So, would adding a hi-flow 3rd cat and a resonator hurt performance of the S/C? If so, how much will I lose?

 

i was waiting for your reply ok, i guess i was wrong. i just remember reading somewhere that there was a mod(s) that worked better if you didnt "free flow" the entire exhaust. thanks!

 

SC performs much better with as little back pressure as possible.

NA (normal aspiration) performs better (subjective drivability) with some back pressure.

Most TL's with a SC will destroy the primary cats eventually. The primary cats will disintegrate (crumble). The broken pieces will create obstacles in the cat and also in the third cat further downstream. For this reason, it is highly recommend that no primary cats (not even aftermarket primary cats) be used with the SC. Also, a supercharged TL engine (J32) will produce much more power if no primary cats are used.

The third cat is ok. The third oem cat flows fairly well. There have been no reports from other TL owners of the SC ever destroying or hurting an oem third cat. But of course for the ultimate power possible, no third cat is advised.

 

Thank you! ATLP's website mentioned about their hi-flow 3rd cat contains 200 cells (not sure about RV6's tho), which is much more free flow than the 900 cells oem cat. What about a resonator(s)? Those guys are pretty much free flow as well right?