Exhaust size, 4 or 5 inch?

[rluft]

Those of you in the 'know', which is the better size exhaust 4" or 5"? My signature shows what I got, and I will eventually get the BHAF and an exhaust brake would be nice. It seems to me that a 5" exhaust would be overkill and may even kill some of the torque. The 4" seems like a good choice and there are certainly alot of folks making them. I don't like noise, I want cooler exhaust and more power.

 

[01smokinram]

Exhaust

I'm running a 4in exhaust. I like it but i want stacks to keep every thing cool when i put my foot on the floor. If you keep what you got in there,then the 4in exhaust will be enough to keep every thing in check.

 

[Mark Craig]

Size Matters

Rluft,



I may get abused for this but, in our testing unless you have a seriously wild truck with nearly every mod that can be done to the engine the 5 inch is too much. I am not a mechanical flow engineer but have worked with them in the process of new system designs and the flow capability of a true 4 inch mandrel bent system way out flows the output capability of the 5. 9 engine. We have also seen a movement of the torque curve upward into the rpm band when a 5 inch is used. Most folks want a diesel for low rpm torque and moving the curve up is now helpful.



Now if you're into sled pulling and making the max hp and torque now matter what the rpm then 5 inch has it's place. There are those that like the sound of 5 inch too, and get it for that reason alone. Call us if we can help you, we've been down this road already and can save you the time and effort.



Mark Craig

DPPI

 

[RBallard]

I have had both on mine, 4" with muffler, 4" straight piped, and currently 5" straight piped. (I like to play). The 4" straight pipe seemed louder than the 5" but I like the sound of the 5". Do I need 5", absolutely not but I bought it for the sound. It all depends on what your looking for and how much you want to spend. 4" systems are a lot easier to come by than 5".



You shouldn't have any loss of torque, the turbo provides all of the back pressure necessary for the motor.



Bob

 

[Devildog]

I got from a reliable source that you don't need 5" exhaust until you reach the 550+ HP level.