Hi there!

I'm planning to upgrade my exhaust system, currently I have the Hooker 2055 headers with a gutted cat and the stock catback except the flowmaster 80s muffler, so it's just a 2.5" intermediate pipe and 2,5" inlet + outlets.

Looks like my engine has some trouble breathing out freely - on the intake side there shouldn't be too much restrictions ( maf descreened, 52mm tb, stealthram intake, afr195s )

The hooker's will be replaced by Dynodon Headers, which have 1 3/4" primaries and i think it was 2.5" collectors.

At the moment I'm currently not sure if I should go dual cat or single cat (no chance to pass smog tests in germany without one *g*).

Would a dualcat setup be a benefit in any kind performance wise?
I'd still have to stick with a single pipe to the muffler, true duals would be a no go, even if I like to.

Next problem is: 3" or 3.5" catback?
If I used a dualcat setup, i'd have 2x 2.5" merging into 3 or 3.5" i-pipe.
The singlecat setup would have a 3" cat outlet, so would a 3.5" i-pipe make sense here?

What muffler could be a good choice for me?
It would be nice if it was a little bit quieter then before with the fm80s.
Some years ago I had a Magnaflow muffler on one of my previous T/A's. Just a 2.5" but it was a bit quieter than the flowmaster and sounded more powerful in the higher rpm ranges, but that was just a stock L98.
Another thought: Somewhere I read about "sound morphing mufflers" which lets your car sound more exotic, forgot which brand sells those mufflers but this could be interesting as well.


Hope you can help me

Alex

 

Dyno Dons, headers/single Y pipe, Random Tech cat, any mandrel bent 3" intermediate pipe, Powerstick muffler and a spout. Loud but good. This is mine w/o a cat.

 

Stupid double post!

 

Sounds really great, maybe a little bit too loud, the powerstick muffler would probably be a problem passing the 2year safety checkup routine here in germany. Should be something more or less looking like the original muffler.
Never heard of the randomtech cats , looks like they are superior to most other converter brands? By now I was just looking for a magnaflow converter and was wondering why they all have such a low pricetag.

 

If forced to run a 3" catback you will want one with straight thru muffler like magnaflow. Thats going to be less restrictive

If you can dual cats should be less restrictive than a single 3".

Only 3.5-4" catbacks i know of are from Mufflex. Good systems and recommended for your combo with the hp it should make. I dont know if anyone has a 3.5-4" single cat tho

 

Dyno dons dumping out a magnaflow catback

 

Strange thing is, on the Mufflex Website they write the 3.5" system is good for 325-400hp , if that's true i'd better stick to the 4"system. Looks like there is an over-axle 4" setup as well.
With my 2.5" stock piping I still get around 380fwhp, but the power curve flattens at ~4800rpm where it still should climb up to +5800-6000rpm, at least somewhere in that range.

@Orr : Your previous 4" setup sounded very nice, did you use single/dual cat or no converter at all?

 

No cat on mine and it was a long tube header

Mufflex is underrated and more like wheel hp. There are guys making 400+ whp on single 3" but it is a restriction. Cutout usually sees 10-20 whp more depending on location. 3.5" should cover 450 whp pretty easily and a single 4 is good to up over 500 whp. More is possible but pipes start to become restrictive

 

do a search for my screen name on the exhaust board. My GTA has a similar engine to yours. I'm running Dyno Don headers, and I made a custom 2.5" dual cat Y pipe and a custom 3.5" cat back with a huge magnaflow muffler in the back. It is barely louder than stock and supports the power quite well. I've got decent pix of it on here if you search.

 

https://www.thirdgen.org/forums/exha...fab-3-5-a.html

 

Thanks alot, bookmarked your thread. This looks exactly how I want it on my GTA.
Do you have a sound clip or video online?
Your muffler seems to be rather big, do you know which part number it is?
http://www.summitracing.com/parts/mpe-14151/overview/
http://www.summitracing.com/parts/mpe-12909/overview/

Looks like you have the second one?

 

Yes the muffler I'm using is the 2nd one you listed. I wanted to use the largest muffler I could package under the car to keep it quiet. With this muffler and dual cats it is very quiet. It's a little bit louder than stock at an idle, and at WOT it has a very deep muscle car roar. It does not drone or resonate at any rpm and inside the car with the windows up it is so quiet and smooth that I forget to shift into 6th gear sometimes LOL.

Unfortunately I do not have a sound video of it. Look for Hooker Aerochamber cat back exhausts on thirdgens or LT1 4th gens on youtube, they sound similar to my GTA at WOT and revving up. Mine is slightly more mellow and muted with no snap or backfire at all. At idle my car is much quieter, again barely louder than stock.

 

Sounds very good. Looks like that's the way I'll go.
If it is too much silenced, I still can weld in a cutout or fabricate a borla-style plate system.

Thanks to all for your help!