jakeb

iTrader: (9)

I am looking for suggestions on what to buy to build a quiet exhaust setup?

I am swapping a ls1(99) into a 85 BMW 5 series and it will be my DD so a quiet exhaust setup is a must.

I only have room for one muffler out back or two bullet type stacked on top of each other.

I am planning on running cats...not sure what brand yet tho.

I was even thinking of buying a center section out of a 2010 camaro and then another muffler behind that in addition to the cats before the center section.

I like a pretty tight sounding exhaust with little to zero rasp/popping/etc.

I am fine with either running 2 pipes or 1..... 1 would probably be easier with the space I have at the back of the car but...open to ideas right now.

Any help is appreciated. thanks!!

52 Rat

iTrader: (4)

The Flowmaster Hushpower is not loud at all and is very compact.

arthropraxis

Borla scored near the top position for both power and low Db in this test https://ls1tech.com/forums/generatio...al-street.html
You should have room for a bullet style muffler in the I pipe. Some are only 5 inches around. If you are going to run cats that should help, too.

gofastwclass

iTrader: (2)

As soon as the weather gets a bit warmer I'm doing something like this for my sleeper...
https://ls1tech.com/forums/15600617-post24.html

jakeb

iTrader: (9)

What do you think of this setup for quiet...
a set of magnaflow cats (or stock cats if I can find some reasonable)
2010 camaro L99 resonator with X pipe
like this


Then the biggest magnaflow muffler I can fit in the stock location. I am guessing it will have to be something like this. The 3" would be at the outlet

FastKat

iTrader: (10)

One important consideration is the diameter of the tubing. A smaller diameter will give you a more quiet exhaust. Larger diameter is generally going to be louder. Only make the diameter as big as your engine needs - bigger isn't always better!

If you search around, you will find charts that tell you what size pipe(s) you should be running for different CFM of exhaust flow or HP. I ran mandrel bent true duals that go from 2.5" at the exhaust manifold down to 2.25" after the catalytic converters and then through some straight-through mufflers. It's pretty quiet, especially considering how small and wimpy my two mufflers are. My setup should be good for about 700hp. I used the charts in Corky Bell's "Maximum Boost" and "Supercharged" books, though it looks like they are also applicable to properly designed naturally aspirated engines as well.

Jimbo1367

FASTKAT,
Thanks for sharing. Very good info. I want my swap to be quiet.

aknovaman

iTrader: (7)

http://forum.grrrr8.net/showthread.php?t=10801

Best thing since sliced bread, imo

V8Rumble

iTrader: (9)

THIS thread is awesome - keeping the exhaust quiet is one of the things that I'm doing as well!

I totally agree - but -just playing "devil's advocate" here- I had a conversation with Denny (one of the owners) at Mufflex, & he gave me a "recipe" if you will for a quiet exhaust (I think he referred to it as "pretty stealthy") - that's 4" in diameter! I just need to find the piece of paper where I wrote the specifics down, & I'll come back to this thread & post the info.

Think you could post the page number from the "Maximum Boost" book? I've got it sitting right in front of me, & I'd like to see what he says my setup is good for... Thanks.

jakeb

iTrader: (9)

I am about to pull the trigger on my exhaust parts but wanted to bump this thread.

Right now I am thinking....
2.25" off the manifolds (stock 98 fbody that are hacked up a little)
2.25" cats
dual 2.25" in, single 3" out Spintech 3000XLP
3" into the biggest magnaflow I can fit

Should I run something different ? Again I want it VERY quiet

jmilz28

iTrader: (13)

Didn't see it explicitly stated so...true duals.
Use an X-pipe.
Magnaflow hiflow cats will quiet things.
Magnaflow mufflers, the biggest one you can fit, flow well and are quiet.
I prefer the largest diameter pipe I can get, LS motors love to breathe.

See how you like that, quiet with no compromise in power or flow. YOu can always throw some bullets on if it's too loud. Another option would be large diameter factory mufflers.

jakeb

iTrader: (9)

I really don't have much room for true duals near the back of the car unless the piping is pretty small (2" or under)

Pro Stock John

iTrader: (34)

2.25 pipe? Restrictive. Why bother putting the engine in if you are gonna choke it.

jakeb

iTrader: (9)

The outlet of the manifold is only 2.25"....

I have some space concerns but I can run 2.5" after the manifolds if it is going to make that big of a difference...

FastKat

iTrader: (10)

I bought a copy of Maximum Boost, loaned it out, and never saw it again. I bought a second copy, loaned it out, and never saw it again. Agh. I have a copy of "Supercharged!", also by Corky Bell. It is on p184 of the "Secondary Components" chapter. If you have a copy of Maximum Boost, find the chapter with exhaust stuff in it and look for a chart with pipe diameter and engine horsepower. I think it's towards the bottom of the page. FWIW, I think the chart in Supercharged! and Maximum Boost is the same.

From what I understand, when you're building an exhaust system from the exhaust manifold (or header) flange back to the tailpipe, you start large and go small. For instance, my C6 Corvette manifolds are 2.5" ID. I have 2.5" elbows that go to 2.5" Magnaflow metal-substrate cats. Then, about 9" after the cats, I have reducers that neck the size down to 2.25". The idea is that as the exhaust gases get farther away from the engine, they cool. As they cool, the contract. In order to keep optimal exhaust gas velocity, you need to appropriately neck down the pipes so that the contracting gas will still have the same velocity as it makes its way through the system. Of course, this is impossible to do perfect, but it gives you a goal to chase. Where to neck down is a whole different topic of its own.

When talking about exhaust pipe size relative to noise, I think the size of the actual tailpipe sticking out the back of the car has a lot to do with it. There are a lot of stock mufflers that have large pipes going into the muffler and smaller pipes coming out of the muffler.

Agreed. An X-pipe is going to help you out. Get it as close to the engine as possible. H-pipes will help too. Also, Magnaflow makes good stuff. Their cats will quiet thing down.

FastKat

iTrader: (10)

I've seen these on GM intakes. They must work!

arthropraxis

I have a three inch system from the header collectors to the tip of the exhaust. It has two cats merging into a single pipe out to one 18in magnaflow muffler and it is almost too quiet.