HotRodK

I started a question in someone elses thread the other day and now (as usual) you guys have me second guessing my exhaust choice. This is going to be the first time that I have modified a diesel beyond the basics, so I still have some newbie questions.

OK, so I have already bought the 4" to 4" turbo elbow (04.5+ style) and clamp. I was going to go with either the MSRB or ASNA 4" turbo back kit. Now I have been reading that the 5" turbo back will drop the EGTs another 150* over the 4". I really dont think it will give me more power, but just the additional drop in EGTs may be benefitial enough to warrant the size change. The larger exhaust supposedly sounds REALLY good without being to roudy and loud. I will be going to the slightly larger '04.5-'07 turbo (when I can find a good used one) in the near future, but probably not much more than that for quite a while. I think either size would have plenty of flow for that setup. Im one of those "do it right the first time" kind of guys, so I really would like all of your opinions on this before I lay out my hard earned cash.

As always, thanks for your responses!

wap

The ONLY reason I would run 5" vs 4" one a truck with less than 700 hp is for the sound. I highly doubt you will see any more egt drop with a 5 vs 4 at your power level. I know when I did mine, I went from 4" srtaight piped to 5" and the only differance I could see, feel, or hear with the exhaust note.

Some may have had differant experiences but I would just run a 4" straight pipe unless you are that poticular (I am) about the exhaust tone.

Just my .02.


Also, do a search, this has been discussed many, many times.

Big Deezul

5 inch sounds awesome

Mighty Goat

Ok, I did what you did on an 03, Same Motor.... The 04.5's just have aaaaa liiiiitllllle different tone. But, I put the 04.5 elbow on the 03 before I sold it. With 5" stacks. It made it sound great but untill you get up in the 650HP or maybe even higher... it's a waste. However, no one can argue the simple fact that it is better. When gas heats up it expands rapidly, and VERY hot gases come out of your turbine, so, therefor you should give it room to expand and get out of the way for more hot gas.... Get the point? Just go 5" once and be done with it. I'm trying to buy a Down Pipe right now to build another stack setup... USE THE SEARCH FIRST

good ole boy

our trucks come with 4" exhaust so that is why I went with 5" when i upgraded

jrussell

Will is right on. 4" has been proven to support 600+hp. If you're expecting a drop in EGT's with 5" you will be greatly disappointed.

IMO the only reason to run 5" is either the louder sound or because you have a larger turbo with a 5" outlet.

omaharam

4" is fine for you as has already been said.
I do have to add one other thing about your post, however.

You said you like to do things right the first time. Do not waist your time and money by going to a newer stock turbo unless your plans are to use it in a twins set up later on. If you plan to stay with a single, you should at least go to a 62 from HTT or II.

jwb600

if it came with 3.5 or 4" to start with why go back with 4" again that is pointless to me. but I had a 5" on my truck when it was stock because I like the looks and sound. ive rode in a couple stock trucks with 5" exhaust and guys say it kills the bottom end bla bla no it does not hurt them. plus 5" doesnt cost what it used to its as cheap as 4" now so why waste the money on a 4" system when you can have bigger pipe thats my thoughts

06CTDforAU

4" supports quite a bit of HP as already stated if you are worried about that.......

I went with 5" purely based on the sound. It takes away a lot of the raspy exhaust note that the 3rd gens are notorious for and really brings out the deep notes in the exhaust.

rip 112

Honestly its not a big deal, but you can lose too much backpressure going to 5" without having the airflo, and in turn lose a little power. But not enough to worry, its really just the sound everyone looks for. I just went 4" with my stacks to 6" tips and its been fine, sounds great.

HotRodK

My thinking was that I can get a slightly used stock turbo off of a '06 or '07 for pretty cheap. Just a ballpark figure, how much is the turbo your talking about?? Can someone get me a link to HTT, please?

HotRodK

The '03-'04s are 3.5" all the way through the muffler then 4" to the tip. Thats going to be a big improvement going to a 4" turbo elbow and 4" turbo back. I just dont think the 5" is needed but 4" should be a quite noticable.

rip 112

You'll be happy with 4", I guarantee it.

I paid right at $1600 for my 62-71/13ss, but a normal 62/12 should be considerably cheaper. I opted for the SS for the better wastegate design and better heatsink capabilities. It screams and makes the truck sound awesome.

For the record I still use the 3.5 elbow on my truck just never thought it would hold me back, and it doesn't, the truck runs just fine and probably spools a little quicker because of it.

HotRodK

The $1600 part is what Im trying to avoid. Some guys have gone with the newer factory turbo and it makes good power on the '04s. They are cheap too, running just $200-$300. If that gives 40hp/75lbft, thats great bang for the buck.
I may be wrong, but doesnt having the 4" elbow help quicken the turbo spool? Less restriction/more flow should help that to a point.

rip 112

That would slow spool, the smaller diameter makes for a little more backpressure which would load the turbo up more, going bigger will let it breath better lowering egts sligtly but slowing spoolup. Mind you these aren't drastic differences, but in theory this is how it works.

If you are only looking for 450hp I'd say the stock 04.5 turbo will work fine, but with a new turo like a HTT it will be upgradeable should the need arise you need more or you want diffrent characteristics like more top end or mid range. I know its alot of money, but I wouldn't have it any other way for now. In the future, maybe a s400 under that.