Someone dosent understand how a Diesel engine let alone one thats been turbocharged works. A 600hp ISX cummins will flow over 3000cfm at 2100RPM at 900 degrees exhaust temp after turbo, on the intake side its around 1400cfm. There is a reason engine manufacturers use 3" plumbing from the turbo to the intake manifold and 5" coming out of the turbo charger.
Factory pete's are 5" stacks or you can option for 7" top stacks from the factory but they are still 5" pipe behind the muffler guard.
If you were an owner operator and toyed around with different setups you would not think that is stupid. That’s how you do it. You cannot go 8 inch all the way to the turbo. You usually breakbit down right there. Even at that point, there will be very noticeable exhaust note difference when switching from 5 to 6inch pipes, or 5 to 7 or 8 inch. The wider the stacks the deeper the note. Stack size and sound note is personal preference. Why do you think it is stupid where you have to break it down? How else would you do it? People don’t put pipes on to have the truck breath better. It’s for appearance and sound
Pretty sure the entire exhaust system on my KW is 5" from turbo to stacks. Gotta let it breath. Trying to force all that hot air down a 3" pipe is just choking off performance.
It's all to make your truck as obnoxious as possible at the expense of visibility. Ever see them have to open the door to see down the side of the truck?
