Hi Guys, Doing a budget race build on a gsl-se (lemons)

I need to put the cheapest exhaust possible on and keep things below 92 decibels.

My plan is to just run a 3" exhaust from the header back to a random magnaflow/ any baffled muffler. (yes aux ports will be removed)

My basic understanding is the greater the volume of exhaust that can be moved the better?

Remember this is a track only car so if it sounds like crap I'm not concerned.

Thanks!

 

It won't be anywhere close to 92 decibels. It will be the loudest thing you've ever heard.

 

You will need two random mufflers at least to meet the decibel limit. Just get a couple big ones off a big American made car and strap that to the end. May have to run one along the bumper and use a downturn tip pointed away from the testing rig. I've read that trick is good for shaving a few decibels.

 

You could always just extend your muffler tips 20 feet in the air.

 

You would be better off with a 2.5" exhaust.

I ran just one magnaflow in the rear for a few days. it sounded like a prop airplane taking off, way over 92db. I than added a second 18" magnaflow and that helped a ton.

 

run an FC exhaust manifold, it looks the same, but the outlet is 50mm instead of 40. then run 50mm ID pipe, which is like 2.25" OD. you will need a muffler in the middle and one at the end. the one in the center needs to be straight thru, non louvered. the end doesn't matter too much, but the bigger the better

92db is quiet, the stock car is borderline to pass that

 

The previous owner of my GSLSE had an FC Racing Beat header into a 3" exhaust with two Magnaflow 3" mufflers.

It was intolerable. It sucks, but the rotary exhaust parts are expensive for a reason.

My car is still noisy with a GSLSE Racing Beat header and pre-silencer into a new stock muffler.

 

So my plan now is to put 2.5" pipe with two magnaflows.

As I said this is a track only car and I will assuredly have earplugs in... just don't want to be told I can't run because of noise ordinances.

 

The bigger is better thinking is best left to the turbo cars since the turbo itself is responsible for both killing pulse scavenging and providing the largest exhaust restriction.The bigger the exhaust system after the turbo,the better.
Bigger exhausts have the effect of making more noise and rotaries excel at that on their own. Even the noise quelling nature of a turbo can't really quiet them.

The only time my car was even close to quiet like stock, was when I ran a merged S4 manifold,turbo,precat,main cat and my RB muffler with a 2.5" system.....In other words,smog test time back in the day, with my S4 TII system! It was quiet,but I was stuck at about 220-230 hp.
I now run a full 3" system after my split S5 manifold and turbo and even with a main cat and a RB muffler,its still louder than I would like it. An N/A rotary with no cat and a 3" system would be intolerable unless the entire exhaust was comprised of mufflers,end-to-end!

 

Wow... you have all successfully scared the crap out of me.

Car goes to the exhaust shop tomorrow morning. I'll let you know how it turns out!

 

Whats up man, good luck on the exhaust set up. If you end up not liking it though, heres my suggestion based on your priorites of quiet 1st, cheap 2nd, power last. So starting with the setup you said you were putting on (header, 2.5" piping, 2 in-line 2.5" Magnaflows) which I think might still be too loud, heres what I would do:

1. Put a Racing Beat Presilencer (2" inlet/outlet) on the end of that header ($177 or cheaper if you buy a used one)

2. Hold on to that 2.5" piping & Magnaflows until the fiberglass packing melts internally (youll know when that happens because your car will start sounding real crappy and also get louder).

3. Once that happens, cut everything out after the presilencer and run 2.25" piping from the Presilencer to a Racing Beat "Street Port" Main muffler ($330). This Muffler has dual 1.75" inlets that merge into the 2.375" inlet of the actual muffler, simply hack the dual inlets off so your going from 2.25" piping to the 2.375" inlet of the muffler and youll be set.

This setup is quiet (unless you have sensitive ears like Campaiar lol j/k buddy ), flows good, is better suited to your motors power band and is cheaper because you wont have to keep replacing fiberglass packed "brand x" mufflers, especially 2 at time like you have now. Anyway, thats my $.02, good luck!

 

Thats what I did basically.
I cut the entire inlet pipe off the RB muffler and welded a 3" ID flange right near the front wall of the muffler.Yea,its a bottleneck compared to my 3" system,but its far enough downstream I figure some cooling has occured by that point (not much!) and its never kept my from making good topend HP,even at 15-16 psi. Its pretty quiet,but gets louder under boost/revs......all depends on your ears.