I am just about to buy a AFE stage 2 intake but i am wondering will it hurt to run a 5" straight pipe (turbo back) or should i stay with a 4" i pull some but mostly drive about 60 miles to work a day

 

I can't see it hurting performance in any way. It won't increase perfomance either. If you can buy a 4" system for cheaper, I would do that. 5" is over-kill...unless you have gobbs of power!

 

Some say 5" actually dynos at lower hp than 4"... if your under 500 HP. I have no personal proof of this. But 5" straight pipe is very loud!
As stated 4" is cheaper and as lot easier to install. Clearances can get tight with a 5".

RJ

 

between the 4'' and 5'' i ran them both straight pipes and the 5'' my turbo would cool down faster on the highway when pulling a single car trailer it was loud but not horrible it wasn't bad to install except for the downpipe off the turbo i ran a 4'' downpipe then 5'' back 5'' downpipe would either rub the trans. or the frame and vibrate the cab http://s117.photobucket.com/albums/o...t=P1170177.flv
can't really tell how loud it was but it sounds alright

 

I love my 5". Some say it MIGHT lose a few hp. But I don't care. I didn't notice a difference at all. As a matter of fact, I feel like my truck came a little more alive when I installed the new exhaust. It could finally breathe. I haven't heard a straight 4", but I heard the 5" has a deeper sound. Either way it doesn't really matter. Check out Markoidaho on ebay. I got his kit and it was very good quality and fitment. Not to mention that it was a great price too! Just keep in mind, a straight pipe exhaust is LOUD!!! And there is a deafening drone at 2000-2150 rpms. At first I was thinking about getting a muffler, now I got used to it and I like it. For regular driving it's ok. But I don't know how it'll be when we load up the camper. Hopefully the park ranger at the camp ground won't get on my case...

 

what gauge should exhaust be? 14 or 16? I went to the scrap yard and they had a bunch of 4" and 5" tube, but it was like 18 gauge aluminum so it wasn't strong at all. I couldn't find any stainless or carbon tube otherwise i'd have a 4" straight pipe installed.

 

I have a 4 inch straight pipe, my friend has a 5 in straight on his cummins. His sounds even more like a semi than mine, it is very loud when he gets on it. It is very loud with my 4 inch but I am also not planning on making gobbs of HP, just a moderate amount. My friend is planning on making alot with his truck thats why he went to 5 inch. Like someone else said, the clearances are tighter under the truck with 5 inch. I'd love to step up to 5 inch, it sounds very good, but I don't need that much pipe under my truck right now.

 

I didn't notice any HP difference.. but I have been on the dyno with the 5in.. I went from a 3in straight to the 5in with a muffler.. and thought that the interior noise is about the same... but I almost liked the sound of the straight 3in better.. (outside.)
Bryan

(Mine has a 4in down pipe.. 5in from there out... )

 

When I first got my 03 i waited a whole 30 min drive to my exhaust guy and we put a 5 inch straight pipe on my truck, it was awesome since then no body really had 5 inch. In fact i was the first guy in the Bryan/College Station area to have it. It was great, so I thaught. Around town and on trips that were only a few hours no big deal., then I moved to Wyoming. As soon as I could when I came back home for a holiday I went to my exhaust guy and put a muffler on. On the 18 hour trip to and from Wyo the constant drone sound by my exhaust drove me crazy and actually gave me a headache, which never happened with any of mmy other trucks but they were 4 inch straight pipe. Since then I have gone through at least 6 other exhaust configurations and now im running the good old 4 inch straight again, but at this time next week i will have custom cut 6 inch stacks with a 5 inch turbo back setup. I will put an AERO TURBINE muffler on if the incab noise is too much. I really believe in those mufflers and I did see between a 100- 200 degree drop in EGTs running that muffler in the past.