Exhaust stack size

All depends on how you like the looks of big pipes, they change note of ex. too big an I have herd some loss of power at bottom end?

 

i think they look kinda goofy after 6 inch

 

Mine are 5 in and want to go for 6 in and place Pittsburgh Power muffler.

 

6" stacks, miter cut, that exit just a hare above the cab (dump truck) are pretty loud on my 5EK 3406.

 

don't mean to highjack thread but do you think its worth it to swap out a single 5 inch stack 3 ft long to a 6 inch 3 ft long?. looking for slight increase in mpg 530 hp dd15 09 long haul app.

 

I don't think you will see any mpg gain staying after the muffler

I have 6 inch now, but think I would like to have a set of 8 inch miter cut. They can be too big I think and hurt the trucks sex appeal and performance.

 

Larger diameter stacks are quieter.

 

we put a lot of miles on so even a small increase would be worth it. cant change muffler cause we have a dpf

 

The fuel increases as slight as they are come from less restriction, and heat at the turbo which is caused by restriction. The engine works less getting rid of waste simply put. With DPF and having to leave the muffler you are not getting rid of any restriction. The 6 won't flow any more than the 5 leaving all the bends, the filter and the muffler.