Am throwing around the idea of putting on a new exhaust system. What size do most of you run? This is on an "01 Cummins.
Everyone have a Happy Holidays

 

4" is good for about 500hp, 5" even more and a deeper sound. They both cool EGTs quickly. It depends on what you are wanting to have.

 

I went with the 5" to allow for future upgrades and power levels, as well as the tone it produces. When I installed my compounds everything went really smooth as the outlet of the S400 was 5" and coupled into my existing 5" system. I prefer to go overboard on mods so I don't have to do it again because I didn't go big enough.

 

I had a MBRP 5" turbo back system and i loved it! nice deep tone. the only reason i got rid of it was i wanted stacks But I still used the MBRP 5 inch muffler and bed kit! In my mind the 5" sounds better than 4" but thats just me!

 

unless u plan on goin for a higher horse power truck, it will actualy hurt u more than help from what i had readon a website somewhere that had dynoed different exhausts. they said the 5 inch hurt the hp untill it got over 500. 5 inch exhaust on a street truck is like someone putting 8" or bigger stacks on there truck. its poitnless

 

IMO 4" looks like a stock size and is somewhat quieter. For these reasons I went with a 4" and it was perfect for me.

 

i have 4" to 6" stack and i love it

 

I went from a 4" to a 5" and I am super happy it sounds great and didn't effect my trucks performance at all

 

i just put a new 4" on mine two weeks ago it had a muffler but it had to go.. i put a 4 to 5 exhaust tip and i love it sounds great to me

 

I have 5" turbo back into a 6" tip, sounds great and I love it