Custom Exhaust Question...

[Enginerd]

Team,
I'm going to bolt up LTs and Cats this weekend. For those of you who have done this already, I'm looking for feedback regarding muffler placement and sound. Where did you put your mufflers and what mufflers did you use? Although slightly different for '05, I'm concerned the only place I'll have room to put mufflers will be way out back just before the tips...not having much pipe after the mufflers could result in an excessive (if there is such a thing ;) ) amount of popping/snapping during coast downs and between shifts (M6). For those guys that have their mufflers way out back, how do you like the sound? Any info regarding custom exhaust with LTs/cats would be appreciated...

:hail: Thanks in advance :hail:

[CMNTMXR57]

I think SW's setup is the only system with mufflers out back by the tips. Everything else is fairly close to the stock muffler location. Going the 4" round bullet style like SLP does allows you more freedom with placement. Trying to fit a muffler into the stock nook in the floorboard will be next to impossible honestly.

The stock muffler bodys are 10" and 10.25" long and a 4x9 style unit. They are very short and don't have a lot of pipe out the back ends as they turn right away. Aftermarket mufflers anywhere near that size usually have 2" of extra pipe which needs to be cut down and then welded to the tailpipes as you can't slipfit anything over that close a bend.

[swmn]

A rare occasion indeed to add something after CMNTMXR57 has checked in.

I do agree with everything he said, don't get me wrong. Basically you can use the factory mufflers or use aftermarket bullet style mufflers. Those are your choices right now unless you are up for some serious fabrication.

If you take off the right side rear underskirting from an 04 you can fab up another heat shield like the one on the left side and put some good sized mufflers between the rear axle and the rear fascia. I think I am going to get away with 4 or 5 by nine ovals, case length is undecided, but the flow numbers are more than adequate.
See: http://www.dynomax.com/documents/ultrafloss_specs. pdf

Total distance axle to fascia is about 35", subtract for bends front and rear.

Sounds like you have already gotten that far and realized as I did about the rice crispies (tm) commercial in lifted throttle situations.

The two options I see are:

1. balance pipe L to R behind the mufflers and ahead of the tips. Better than nothing, but not a lot of help.

2. (I just thought of this one) Maybe drop the center underskirting, and run left muffler to right exhaust tip and vice versa, with maybe a very short H connection between the tail pipes?

[Enginerd]

Yeah, I was hoping I might be able to work an X-pipe in somewhere to help with the crispys...think I might have to wait until everything is bolted up and go from there...thanks for the info fellas...but anyone else, please feel free to post more info...this site be da bomb-diggity yo :-pimp:

[CMNTMXR57]

Thanks swmn.

My whole issue with fabricating something was what to do right after the mufflers. That's where the stock setup has such a tight turn that is hard to work with unless you go to a smaller muffler. But we already run a small muffler, so you're back to square one. :D

[swmn]

I spent a long time looking around for parts to put in a quad system. I was hoping to start with a pair of Y's in one 2.5" inlet to two 2" outlets at the front flange, two small mufflers in the stock holes and then two more small mufflers out back. Then bring the two left pipes back together and the two right pipes back together...then (even if I had found flow #'s around 220cfm in a ten inch case, which I didn't) there isn't enough room left to run enough dual pipe to keep it quiet under varying throttle and vacuum conditions.

As you say, square one.

[Sam 04 GTO]

Give me a shout, the guy who fabbed my exhaust can make you whatever you want. He's here in Vegas, and has a mandrel bender.
:)
497-9419

[swmn]

We don't need benders, there are talented professionals all over the country who are sick and tired of putting bolt-on flowmasterrs on F-150's just to stay in business.

What we do need is a combination of mufflers that will:

A: fit under a GTO without giving up ground clearance
B: flow about 880cfm at 20.4" H2O suction (for stock, more power needs more flow)
C: fit far enough forward that the tailpipes can do some good

If your guy can make custom muffler cases, or knows of a source I have previously left undisturbed I would love to hear about it.

EDIT: Sorry I snapped at you Sam. When I said "a lot of time" I really do mean a lot. I've got way more than 40 _hours_ invested in reading muffler specs.

[Sam 04 GTO]

No worries. I just figured I'd help a local guy out. My friend can bend/weld anything, but I don't think he'll make muffler cases. I personally have no use for mufflers, ;)
but if I did, I'd probably run Dynomax Race Magnums.
:)

[Enginerd]

And your help is greatly appreciated!

In fact everyone's is. Thanks again guys.

[Barbados04]

What about the muffler they use for the Corsa exhaust system. There is a picture of it on the Tbyrne website. Do not know the measurements but it looks like it is good to go for the rear area.

[WillieD]

A pair of dynomax bullets sound great on a true dual, x-piped LS1 exhaust system.

When I end up putting something together I plan to get 1 7/8 primary Kooks (probably with cats), 3" true duals with a x-pipe, and run through either dynomax bullets or a pair of twisters.

[CMNTMXR57]

It's not an issue of bending. I can do that too. Matter of fact I had to re-flare some of my piping when I installed my cats because the clamp flat spotted the pipe. :D But I digress.

The issue here with the GTO is space available to fit an exhaust into. I commonly see reference to F-Body's and what sounds good. Well the difference with the F-Body is that basically everything was hung from the car, so you had more room to play with (especially with the muffler location behind the differential) so you could play with lots of tubing configurations from the engine up to the over axle pipe.

On the GTO, the exhaust is recessed into the floorpan and our stock mufflers are already very small and a tight fit as is. The aftermarket choices of mufflers that are smaller in body length is very slim pickings and generally leads to a lot of cutting of end tubing. Your real only option is similar to what SLP did..use bullets. But now you're sorta hanging stuff some and not fitting it into the factory cavities in the floorboard.

Then once it exits the mufflers, you've got some tight bends which makes cutting a muffler to fit a pain as you can't utilize the OEM or SLP style of "slip fitting" the pieces. You almost have to butt end them and permanently weld to get things to fit.

Those are the challenges we face.

[swmn]

The thread that won't die, eh?

Briefly, about the rice crispy sound. Try to remember back to the 1984 "Sunrise" by the Assan motorworks. 800cc of fuel sipping mouse motor, brand new out the door under 8k. They were made in some little country Michael Crichton hasn't written about yet.

Trouble is they welded the tail pipes on with coat hanger wire. Twelve days after the city finally put some salt down after the first big snow storm, all the tail pipes rusted off the Assan Sunrises, and now you got rice crispy treats all over town.

No problem at idle, acceptably but not pleasantly loud at part throttle acceleration, quite noisy at WOT. Take your foot out of it to coast down to a traffic light ~~~now do you know the sound?

Now think about bolting a 346cid V-8 on the front of that. What enginerd and CMNT are already looking for (I bet jfulcher will be poring over this thread in a couple weeks the way he is going with his motor) is an exhaust system that can support serious power and still be streetable (ie quiet). Similarly, I am looking to build more or less the same system for my stock motor to get it as quiet as possible for my own reasons.

No bullets need apply.

[Adam4356]

I think if you put all the available systems together the Stainless Works system i run is probably what you are looking for.
It's hard to make a system that doesn't loose much power yet retains some civility. The stainless works system applies a pretty good formula of twin 3in mandrel bent pipes and turbo mufflers that fits in the OE location. Result is a system that still has aftermarket grunt to it but idles and screams with more tone, bartone then just pure rasp dB.

[Enginerd]

She's at the shop right now...got Flowmaster 40s, same side in/outlets (cobra style), turned out great. I'll post pics in this thread if anyone is interested

click to see exhaust porn (http://ls2gto.com/forums/showthread.php?t=15429)