Engine/Transmission (1998.5 - 2002) 4" or 5" Straight Exhaust

[lkuykendall]

I have spent about 4 hours searching and reading forums about 4" and 5" exhaust systems but still can't decide what I want.

I am looking for an exhaust system that will lower my EGT's as much as possible while pulling. I HATE not being able to use the power that I have! My current setup is: 2001. 5, 6 spd, EZ, 275's (soon to be DDII's or Mach II's), BHAF, straight piped (factory pipe) and stock turbo. This pickup is used for towing and nothing else. I am leaning toward the 5" turbo back exhaust but wanted to make sure there are no draw backs to having the 5" over the 4", other than noise. Oh yea, noise is NOT an issue!! I remember reading somewhere that people actually lost power with the 5"???I just downloaded the sound file that RBallard posted and love the sound of the 5".



Thanks for you help!



Len

 

[Cummins4Life]

I've had 5" straight pipe for a while now. No problems with power, I dont know if it helps EGTs that much more than straight 4"but it sure sounds better IMO. One thing I did learn is that no airfilter/intake/exhaust setup will make up for the EGT relief supplied by a bigger turbo.

 

[TomGolden]

Well, I can't say what if any real performance differences there are between the 4" and 5" exhaust systems, but I am fairly sure the common feeling is that you won't see any EGT differences between 4" to 5".



I have the Pinnacle Performance (Jardine) 4" straight piped exhaust and love it. I have not heard a 5" in person, but if nothing else than the factor, I wish I had the 5" straight exhaust, but it isn't worth the $$ to me to upgrade mine just for looks. Actually, if/when I ever upgrade my exhaust, it will be twin 5" or 6" stacks



I would caution that on some trucks, with certain mods, a 5" system may not fit under the truck.



I have FastCoolers on my 6 speed, and right where the pipe passes next to the passenger side FastCooler, a 5" pipe would not fit, unless it was bent a little, or the whole pipe mounted another inch to the outside of the truck.



Tom

 

[NPloysa]

Downpipe question

I am also in the same boat.



I am leaning toward 4" but why not do 5" when I have to do it anyway.



I do have a few questions for you guys running bigger turbos and another about exhaust exits.



Do most of these exhaust kits (either 4 or 5") come with a straight perpendicular exit, or are some bent down and out?



Also, if a stock turbo is 3. 5" exhaust housing, and say I were to go 3. 5" stock to 4" downpipe, to 4" exhaust, OR 3. 5" turbo to 4" downpipe to 5" exhaust, the smallest restriction is still the 3. 5".



Would it be best to go to 5" as soon as it exits the turbo, assuming I have the room?



Nick

 

[Cummins4Life]

Mine exits out the passenger side of the bed at an angle. See my gallery to for a better description. Before the 6" tip I had straight 5" that exited in the stock location at the stodk angle. I have seen some that come straight out the back and turn downs are availible. I have seen that in some cases 5" can be fit up to the bottom of the downpipe. I had a 4" downpipe that fit up to my old PDR35 and it sounded pretty good. Now with a true 4" opening off my PDR40 and 4" downpipe it tends to resonate a little more. I saw a truck from idaho that had 5" off the back of a HX40. It had a 90* down a length of straight pipe and then another 90* pointing towards the rear of the truck. I dunno how it fit or how it flowed but it looked cool.

 

[JBlackwell]

Re: Downpipe question

Originally posted by NPloysa

?



Also, if a stock turbo is 3. 5" exhaust housing, and say I were to go 3. 5" stock to 4" downpipe, to 4" exhaust, OR 3. 5" turbo to 4" downpipe to 5" exhaust, the smallest restriction is still the 3. 5".



Would it be best to go to 5" as soon as it exits the turbo, assuming I have the room?



Nick

I want to know this too.



JD