Unless your High HP 4" is all you need. People go with 5" because they like the sound and are concerned about the tinyness of their tips

 

I have 4" from the turbo back with a custom 6" tip... Muffler MIA

 

I made 683 on my 5" down pipe to 4" exhaust. The compounds require the 5" down pipe but I don't see any real need for 5"

 

01cummins13 - what type of MBRP 5" system did you have, I'm looking for a quiet one?

 

Everything I've read about exhaust flow in turbo application is the less back pressure the better. In other words, a bigger pipe and shorter exhaust would only benefit. Of course, below 500 HP the gain would be very marginal so it might not be worth upgrading from a 4" to a 5" if that was your situation. If you're upgrading from a factory exhaust though, might as well go 5" if you like the deeper sound.

 

no need to go to 5" in these trucks...

I run 5" just because I have twins and didn't see the point in going from 5" to 4" creating a bottleneck.

I also run straight pipe. no need for a muffler with twins. second turbo quiets down the exhaust already.

 

5" will give you a deeper exhaust tone. No performance gain

Luke

 

Great topic everyone! I'm planning to do mine this week and am going to do a 4" with no muffler.

 

I did a 4 inch Afe turbo back kit with MBRP muffler. I later found a 5 inch tail pipe section on ebay, for $60 bucks shipped (muffler-back). I removed the 4 inch tail section and welded in the 5 inch with a 5 to 4 inch reducer, and a 6 inch stainless tip. It looks cool and does not sound any different than the 4 inch. And, no one's the wiser. Just did it for S&G's.