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Discussion Starter #1
Hey I've been trying to decide on the 4" duals or 5". Does anyone have sound clips of the 4" duals? I've been trying to search it out to see if its that different from the 5" single.

Any opinions? I know most ppl have the 5" but anyone with the 4" duals have any feedback? Thanks!
 

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There's one guy on here that I know of that has duals. Check out his YouTube vids. His Chanel name is rohde42. Here is one of his vids

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Discussion Starter #3
Hmm I think I personally like the sound of the 5" better. Thanks for the link
 

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One thing duals has over the 5", the duals help spread the sound out so it seems louder. But the 5" sounds a little deeper.
 

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You actually get more flow from a singular larger exhaust than smaller duals. This is due to the turbulent flow as the exhaust hits the sidewalls of the pipe. You get more laminar flow from larger pipe. So in short you should get more power from the 5".
 

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You actually get more flow from a singular larger exhaust than smaller duals. This is due to the turbulent flow as the exhaust hits the sidewalls of the pipe. You get more laminar flow from larger pipe. So in short you should get more power from the 5".
You are splitting hairs there my friend.
If this were true, I doubt you would see any power gain unless the pipes were fed by a pair of C-18 Caterpillars.

Go with the true duals...
They look better.
 

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Not according to Gibson. Is there a major difference I don't know. But there is one. If you don't think the flow of exhaust matters, then why change anything but the tip? Sound?

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Exhaust flow does matter when there is a ton of mass moving, but the 6.7L does not generate enough exhaust mass to really make a difference between 4" or 5" pipes.
An ISX Cummins 600 will use a single 5" pipe, so I doubt a Powerstroke will see any noticeable change when a 4" is more than enough pipe.

The main reason for large pipes is to lower EGT. With todays high flowing 4 valve heads and decent factory down pipes, EGT temps aren't a real issue anymore. Now, it's more about styling.
 

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It made a difference in my 5.3l Chevy. Have to think it would here.

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Ur argument about hitting the side walls is invalid. it all floats around how much CFM the combined area/volume the dual pipes will flow vf the 5 inch.
 

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I'm done with this. Believe what you want. If you don't believe in turbulent flow then maybe you should take a physics class.

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Chief, in terms of a turbulent flow, yes i agree it can hurt performance, but how many silencers/ curves/ restrictions does a 6.7 have? You also have to take into account the volume of air flow the pipes will flow like i said in my previous post.

Frankly i feel if the duals are designed well, u can get more out of it. Now like on my 6L for example, its not a "true dual" not sure about the 6.7 but its say 4 inch single until the split. the 5 inch is 5 inch all the way from the DP.

Im not saying you are wrong, but there are other factors, diesel trucks aside. Im not just talking out of my *** on this. Principals will carry over from any type of tuning to a vehicle you do.

-Ellery
 

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Frankly i feel if the duals are designed well, u can get more out of it. Now like on my 6L for example, its not a "true dual" not sure about the 6.7 but its say 4 inch single until the split. the 5 inch is 5 inch all the way from the DP.
Unless you were to put a turbo coming off of each head then you can't get a true dual out of a turbo diesel. Or any vehicle with a turbo for that matter.
 

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Thats what i wasn't sure of on the 6.7 is it a compound turbo like the 6.4? Someone posted to go with the "true duals" which is why i mentioned it.
 

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Thats what i wasn't sure of on the 6.7 is it a compound turbo like the 6.4? Someone posted to go with the "true duals" which is why i mentioned it.
no, it's a single turbo that is supposed to act like compounds.
 
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