Well I got my truck running today and took it out and drove it around a bit.

I have the ATS upgrade, 3" downpipe, then it steps up to 4" after the downpipe and is 4" straight pipe out the back of the truck.

Now, at idle and below 1000 RPM the turbo sounds AWESOME! In fact when you're just cruising around in that range it just whistles like crazy.

However, from 1000-3000 RPM it just sounds like a gas V8 truck with straight pipes on it which isn't really what I want.

Are there any mufflers out there that will keep the whistle but tone down the raspiness? I'm probably gonna put a muffler on the truck at this point as I don't really like how it sounds, I just wanted to see what some of you other guys were running that you liked.

 

i love that sound!!! you dont like it?

how much boost is your turbo putting out?

im running a strait pipe, but mine isnt that loud, its actually quieter up in the 3000rpm range... hmmm weird,

 

For a moment there I thought you were after the powerstroke rattle (that would be sacrilegious). Actually I'm in the same boat as you. Strait pipes and turbo with similar results and not completely happy with it. I don't dare engine brake! I hope some one can post their experiences because I'm afraid I have none with mufflers on these trucks.

 

ooh!!! lol, no, that would be sacrilegious!!!! lol
well, engine breaking is pretty damn loud with out a muffler, just dont do it in a non engine breaking zone/hill, i got my self a ticket doing that... stupid cop. lol

 

No I don't like that sound...

All the rednecks here with their Chevies run straight pipe and sound like that. I'd like mine to sound a little more "sophisticated" (hey it is a diesel).

Well, right now I'm thinking about trying a Dynomax 4" Ultraflow as I can fit it right in the current system, and there isn't a whole lot else that is affordable in 4".

Oh and I need to play with the wastegate actuator a bit as I'm only getting about 6 lbs right now.

 

Hey, I take offense to that, just cause we're not sophisticated doesn't meant we're not smart.

 

Well you rather misconstrued my comment, but anyway...

I want it to sound like a diesel, not like some other guy's 1500 Silverado or Ram.

I found a place on ebay that has really good prices on a couple Magnaflow 7" round case mufflers (straight through, 4" in/out). Just not sure what case size I should get. They have a 14" long case, 20" long case, and then a real big boy that is around 30" long overall (I think about a 25-27" case). I don't want it TOO quiet

 

I've been reading about exhaust scavenging in various places, and it seems to me that straight pipes would hurt your torque and power output. The longer the secondary tube (post exhaust manifold or turbo) the better your torque UP TO A POINT, then you have building back-pressure beyond benefit which causes the system to become less efficient. The articles were talking about secondary lenghts of 18-22" for more HP higher in the RPMs, and around 50" for higher torque at usable RPMs. (Those lengths are for a performance 350 sbc, so I'm sure it would change somewhat for a 420/445 cid diesel) What seems to be very important is that there is a great volumetric change at the end of the secondary tube (muffler) in order to make the most of the secondary length. Running a straight-thru "glass-pac" type muffler would almost be an extension of the secondary for all intensive purposes. There are many large oval body mufflers that give you a lot of volumetric change and flow high quantities of air with very little restriction. Look for mufflers for use on big block engines, these would help you with that "sophisticated" sound instead of the "sophomoric" bang-bang of straight pipes.

 

That all goes out the window when you throw a turbo into the mix.

A turbo creates its own backpressure...behind it, you want the freest flowing exhaust you can manage.

 

The muffler info would still apply, I think, since you still want to tone down the exhaust noise. If scavenging is of no consequence, the muffler could be placed anywhere under the truck, not at a specific distance from the turbo.

Round mufflers with straight thru designs appear to act much like a tuning chamber on a 2-stroke. As the gasses enter the muffler they spread out in a cone shape, contact the back side (or wall, depending on the muffler body) which creates a sound-wave that bounces forward toward the inlet. The diagrams of oval mufflers show no such expansion and sonic return, helping to keep the gasses moving outward. I'm sure there are plenty of bench-flow tests that speak to restriction in muffler designs.

It would seem that you have the least restrictive exhaust now, but you don't like it because of noise, so, depending on how much noise you want, shop around for the one that sounds right. Both DynoMax and FlowMaster, along with others, have sound samples on their websites.

 

Here's an article about exhaust, headers, secondaries, scavenging, AND turbos. this might help.

Exhaust Theory

or, one of my favorite quotes

"Not only that, but turbos introduce a bit of backpressure to your exhaust system, thus making it a bit quieter. All of the typical scavenging rules still apply, but with a twist. Mufflers work really well now! Remember, one of the silencing methods is restriction, and a turbine is just that, a restriction."

 

I've been wondering how a chambered muffler would sound? I ran some Hooker Aerochambers on my old Plymouth Duster and it was the best sounding muffler I'd ever used. They weren't raspy at all and didn't drone at cruise speeds like Flow's tend to. Just a nice, mellow, deep exhaust note. The largest one I can find has 3 1/2" inlet and outlet with a 14" case. Don't know how well that would keep things quiet. I do know that Hooker claims that they will flow 441 cfm of exhaust.

 

Well as of right now I think I'm gonna run a Magnaflow. Found a great deal on one of their mufflers with a 24" long core, I think that may be the ticket.

BTW- about the Aerochambers, I've always been told chambered mufflers are a no-no behind a turbo. Something about how they muffle, makes them really bad for a turbo engine. Plus they don't make them in 4".

Some guys over on the turbo 2.3L board said they've seen around 20 hp switching from a Flowmaster to a straight-through type muffler (but, the flowmasters sure do sound cool)

 

That could be. I'm sure a straight through design probably would work best as the turbo is already creating plenty of back pressure through the turbine housing.

I have a buddy that's running a Freightliner muffler on his 8.1 Chebbie gasser. It was from a medium duty truck I believe. He says it flows more exhaust than he can put through it and it cost beans compared to the big aftermarket name brand alternatives. Might be worth looking into.