I'm looking at the 5in shopdiesel exhaust kit. Will going from a 4in to a 5in exhaust increase turbo lag while towing heavy? I was thinking of putting a muffler on it to control the drone. Is anyone using the muffler that comes with their 5in kit or know anything about it? I'm looking for a deeper tone, less raspy than the straight 4". Most use the Donaldson, but I'm looking for a complete kit. Don't want to piece it together anymore. I went from stockthen stuck in straight pipe, then had to piece it together with the 04.5 full 4" downpipe when I put the SPS in.

 

how heavy do you tow?

all i noticed was a little better fuel milage and cooler egts. if spool was affected, it wasnt noticable in my case

brett

 

When I went from 5" straight to the 5" with a donaldson my turbo lit quicker... Not a ton but it was noticeable....

 

Didn't notice significant lag when I changed to a 5 inch exhaust. Of course, with the Torque management function virtually eliminated with the Smarty, well, don't notice much lag at all off the line...

 

I added Smarty and 5" at the same time. All I noticed was better MPG, quicker performance and cooler EGT. Hard to tell as I think both items helped. I do not think the exhaust would hurt anything.

 

I have the stock downpipe to where the cat used to be, then 5" all the way back, and I never noticed a change in turbo spooling, really the only thing I noticed was cooler EGTs while cruising/cooldown.
Ill get around to picking up a 5" downpipe when I can afford a turbo

 

Unless you are upgrading to a 5" downpipe, you will still have the restriction of nearly 3 feet of 4 " downpipe, the 5" will sound better and a bit more throatier. I actually noticed longer spool up times running a silver bullet with the 5" vs the 4".......Looking at the physics stand point, remember back pressure is not good , but too little back pressure allows the turbo to more or less free spool and does not cause enough restriction to aid in building boost as fast. Just what I have personally seen in my setup.

 

not to hijack the thread or anything....but why can't you get a 5" downpipe for an 03-04? all i ever see is 4" and then it goes to 5" after that

 

the shopdiesel kit has the 5" down pipe also for the low low price of $310

brett

 

Towing heavy is about 25k (trailer + dozer,etc). I hauled this right after I put the SPS on and it seemed slow to spool. I haven't had to move equipment around too much lately so I really haven't had a chance to see which combo of boxes/programmers worked the best.
Is the downpipe on the shopdiesel 5" kit a full 5" or a 4" that expands to 5"?

 

They kits are a 4" adapter that opens up to a 5"(because your Turbo outlet is 4" on most aftermarket turbos........Still from the physics standpoint if you have exhaust gases leaving a 4" outlet on your turbo, then a 5" downpipe is unnecessary. You can go with it if you desire but not really beneficial and I can confirm the laggy turbo when using the larger pipes. Picture shoving 10 pounds of shi* in a 5 pound box....5" dp and pipe is overkill when your exhaust is leaving a 4" hole

 

the shot diesel kit and a few others bell right at the turbo so you migh have 3/4 of an inch of 4" piping that just adapts to the turbo..... so essentially you will get better flow... Both time I have put 5" kits on my egt's dropped dramatically of course by bottom turbo has a 5" flange so it is 5" all the way out!!