Diesel exhaust on LSx

[65standard]

I'm building a high compression 6.0. I have shortie 1 3/4" headers dual 3" pipes routed to the right side. I then want to use a single 5" muffler and tailpipe from a diesel truck.

Is a diesel muffler completely wrong for a gasoline motor?

If so, I will use a flowmaster dual 3" in/single 5" out with a 5" diesel tailpipe.
Am I crazy for thinking this?

[BR3W CITY]

5" exhaust? Thats around the size being used on promods. Dual 2.5" should be plenty for your motor. If you want to run 3" thats fine, but there is no reason to have a 5" exhaust anywhere on that setup.

Diesels are moving WAY more air volume, and anything else that needs a 5" exhaust makes 1400+hp.

[65standard]

Well I picked up a single 4" diesel exhaust. My stock 6.0 exhaust is dual 3". I will go from dual 3" to single 4"

Yeah 5" is massive, but it sure looks good.

[indymachinist]

It won't really hurt anything to be massively oversized, but it will be a bit harder to keep quiet/harder to package nicely.

How much power are you expecting to make?

[65standard]

A dual 3" to single 4" is massively oversized? I thought it would be a little better than the dual 3" it originally had from the factory. I should make 450 rwHp. Maybe a little more.

[BR3W CITY]

For the power level you're at, dual 3" itself is actually a bit large, though not what I would call massive. That pipe coming off your headers is only 2.5" (then expanded to 3"). With the 1-3/4 headers, a dual 2.5" setup with a nice xover or single 3" wouldn't be holding you back on power.

Stepping up to an 1-7/8 or 2" primary tube, and another 150hp, then you start to need the 3+" piping. Our Ws6 makes just shy of 600 on motor right now on dual 3".

Build what makes you happy, just stay away from the 5" pipe. There is such a thing as too big.

[65standard]

Well I gave up on the diesel muffler. It is just too massive to fit under my lowered chassis. Getting a custom made 40 series flowmaster with dual 3" inlet and single center 4" outlet. Then a custom single 4" tailpipe out the right side. No catalytic converters so it's going to be a stink bomb. Just wondering what it will sound like.

[69gmcc10]

On my 6.0 1500HD the exhaust in stock configuration was dual 2.75" to the muffler and single 3" out. I replaced the muffler and ran a 4" exhaust because that is what Magnaflow sells for a system on these trucks. It is lout, has a little drone, and raspy sounding and i have had it on for 2 years now, if that is your thing you will like it. I am downsizing to 3.5" tailpipe to quiet it down. My exhaust calculation program says that dual 2.75" exhaust is the correct size for a lq4... But that is not the most available exhaust size on the market, so.

[BR3W CITY]

Originally Posted by 69gmcc10

My exhaust calculation program says that dual 2.75" exhaust is the correct size for a lq4... But that is not the most available exhaust size on the market, so.

I had pretty much the same calc when I wanted to redo mine last year. You can buy the tubing, but its finding enough fittings/joints to complete the setup that gets tough. You end up going up and down so many sizes in the run that its hardly worth it.

[69gmcc10]

Originally Posted by BR3W CITY

I had pretty much the same calc when I wanted to redo mine last year. You can buy the tubing, but its finding enough fittings/joints to complete the setup that gets tough. You end up going up and down so many sizes in the run that its hardly worth it.

Had the same issue here. I had to upsize to 3" at the muffler to get close to what I was looking for.