Exhaust concept for the truck(drawing).....

[moregrip]

I have a couple of questions, I have a 6.0L 2500HD, it seems to have the same exhaust system as the 8.1L, so the question is, is this the same exhaust system as the diesel trucks? and if so, I imagine the stock catalytic converters must flow fairly well. Anyone know what cfm they are rated at?

 

So here's my idea, by my calculations I need approx 1375cfm total to support the mods I have planned. Since I know of no 2 cats that will flow that high, I can use 4, or hopefully, the 2 cats and the 2 pre cats that come on the truck stock in the below configuration.

 

 

OK all you exhaust experts, feed me some info, thanks in advance

[misterp]

Wow this is actually a good challenge, making a California-legal system that can flow 1400cfm. What size collectors are you thinking of using, and what size plumbing? What is the tubing size between the cats and the mufflers?

 

Mr. P.

[moregrip]

Wow this is actually a good challenge, making a California-legal system that can flow 1400cfm.  What size collectors are you thinking of using, and what size plumbing?  What is the tubing size between the cats and the mufflers?

 

Mr. P.

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all good questions. I have not done the calcs yet.

 

previously 3" collectors, and dual 3" exhaust(no cats) would flow plenty well with some left over.

 

I will redo the calcs tonight and post up

[Dylan06SS]

That is one hell of an exhaust system.

[AUTOGUY]

Hopefully you have a Crew Cab with an 8' bed to fit all of that under.

 

I was under the impression the x-pipe should be between the converters and the Mufflers. I guess with your Quad converter set up it might not be feasible.

[BenKey]

I'm not a physics guy, but it seems just because you y-out and go to two cats does not mean that flow will double. Won't that also mean you'll loose some of the velocity to make that flow occur?

 

An aftermarket cat can flow higher than a stock one, although most are not very much more. If you wanted max flow from your cats go with ones from Random Technologies. They flow over 500cfm. But, 4 of them would cost you close to $1k. That's a lot for cats, but probably the only way to even come close to your goal. They will also give you the room you'd need to do that. They look like little bullets.

 

Where/how did you decide that you need that much cfm of exhaust flow? Does it even come out that much straight out of the motor at your collectors?

[moregrip]

I'm not a physics guy, but it seems just because you y-out and go to two cats does not mean that flow will double.  Won't that also mean you'll loose some of the velocity to make that flow occur? 

 

An aftermarket cat can flow higher than a stock one, although most are not very much more.  If you wanted max flow from your cats go with ones from Random Technologies.  They flow over 500cfm.  But, 4 of them would cost you close to $1k.  That's a lot for cats, but probably the only way to even come close to your goal.  They will also give you the room you'd need to do that.  They look like little bullets.

 

Where/how did you decide that you need that much cfm of exhaust flow?  Does it even come out that much straight out of the motor at your collectors? 

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for a zero loss exhaust system

 

2.2cfm for every 1 fwhp, based on 625fwhp = 1375cfm needed.

[misterp]

OK my thoughts -

 

First the cats have to be close to the collectors to even light-off; getting this to fit close as possible to the engine will be the primary challenge IMO. I also agree with BenKey, I would abandon th x-pipe and design a correct pre-muffler chamber, then into mufflers and then tailpipes.

 

 

Mr. P.

[moregrip]

losing the x pipe is completely do-able, is that a resonator chamber?

[misterp]

Yes, a resonator chamber; I was thinking myself of a simple empty oval box that was 4-inches tall by 9-inches wide by ???-inches long being fed by dual 3-inch inlets and in turn dumping out to twin manifolds of Magnaflows.

 

I read a C5 Vette project web page where the guy designed a resonating chamber similar to this (his was like 3 or 4 feet long running through the tunnel of the car!) and reports that it totally eliminated the rasp from the Vette exhaust note as well as made more power. But from what I understand the resonating chamber will have an optimum size (in cu.ft.), in our apps I think that we are limited by space constraints but still a handy guy can probably make an oval-shaped long chamber that might work well in our trucks. But I have not taken a tape measure under there with me yet, I am just guessing on the available space.

 

BUT, if there is not enough room to make a resonator chamber of any significant size then you can fall back and install the x-pipe in its place, there should be enough room for that I would guess.

 

Another space issue is the under-tranny crossover, but again maybe a 3.2" pipe that is squashed flat a bit, like the stocker to give near stock ground clearance?

 

I might go out and lay under the truck in a minute and check it out again...

 

Mr. P.

[moregrip]

Yes, a resonator chamber; I was thinking myself of a simple empty oval box that was 4-inches tall by 9-inches wide by ???-inches long being fed by dual 3-inch inlets and in turn dumping out to twin manifolds of Magnaflows.

 

I read a C5 Vette project web page where the guy designed a resonating chamber similar to this (his was like 3 or 4 feet long running through the tunnel of the car!) and reports that it totally eliminated the rasp from the Vette exhaust note as well as made more power.  But from what I understand the resonating chamber will have an optimum size (in cu.ft.), in our apps I think that we are limited by space constraints but still a handy guy can probably make an oval-shaped long chamber that might work well in our trucks.  But I have not taken a tape measure under there with me yet, I am just guessing on the available space.

 

BUT, if there is not enough room to make a resonator chamber of any significant size then you can fall back and install the x-pipe in its place, there should be enough room for that I would guess.

 

Another space issue is the under-tranny crossover, but again maybe a 3.2" pipe that is squashed flat a bit, like the stocker to give near stock ground clearance?

 

I might go out and lay under the truck in a minute and check it out again...

 

Mr. P.

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thats the nice thing about my 2500HD, with the taller frame there is no need for crushed pipe. And there is more room in general than a 1500 series:)

 

check this out:

[misterp]

Yup you found the Vette project I was referring to

 

Mr. P.

[zippy]

i don't believe you're going to be able to pull that off in california. the law states that you cannot re-locate the catalytic converter to a non-stock location. you are allowed to only change a catalytic converter if the vehicle has over 50k on it or has had a catalytic converter failure before that point. for replacement a larger catalytic converter is allowed and even a free flowing model, but you cannot move the location of it's original placement.

 

i also wouldn't expect you to see a gain at the track or on the dyno from doing 4 cats over 2. all that extra weight is about all you'd end up with.

[moregrip]

i don't believe you're going to be able to pull that off in california. the law states that you cannot re-locate the catalytic converter to a non-stock location. you are allowed to only change a catalytic converter if the vehicle has over 50k on it or has had a catalytic converter failure before that point. for replacement a larger catalytic converter is allowed and even a free flowing model, but you cannot move the location of it's original placement.

 

i also wouldn't expect you to see a gain at the track or on the dyno from doing 4 cats over 2. all that extra weight is about all you'd end up with.

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what do know anyway

the idea is to have some semblance of responsibility

tell me how to keep the cats and flow 1375cfm exhaust

[BigTex]

I'm running a pair of 3" high flow cats on my truck. They use a corrugated metallic substrate instead of the stock ceramic brick. Benefits = much better flow and a higher thermal breakdown temp. The stainless baffles inside withstand heat much better, which in our forced induction setups is a big benefit. There are a few manufacutrers, but as Ben said, they are costly. The powercat brand is cheaper than the random tech brand.

 

My experience with them: I had a dyno done with my full exhaust. ASM headers, 3" pipes into an X then duals out through the cats and into a muffler. I went back to the same dyno on the same week, but this time I removed the exhaust from the X pipe back. So no muffler and no cats. No changes in the tuning were made between dyno pulls. The end result was 4 more peak rwhp without the exhaust.

 

My take on it - I don't think my cats are causing any real loss of power.