4" downpipe design concern

[banjobob]

Wondered if any of you guys know if there is a predetermined distance that is required between exhaust housing outlet(stock sizing) and first 90 in the downpipe. I have determined how to attach to the exhaust housing and blow up immediately to the 4" stainless pipe i am fabricating new exhaust out of. Just wondered if it makes any difference. thanks, jeff

 

[BushWakr - RIP]

I don't know if I'm going to express this right but.....



The radius of the 90* downturn can't be any larger than the original one. Since the piping is larger, you'll need to conserve what room you have to allow for the heat shield and larger dia. tubing.

The beginning of the radius bend starts only about 4" back of the connecting flang..... did any of that make sense, or did I miss the point entirely???



bob.

 

[banjobob]

Ok - Now i might be confused - ( with that being said I must explain that i am a pipefitter and have experience dealing with pumps and blower type arrangements which tend to have certain requirements as to distance of first fitting off face of flange/opening - thus to alleviate downstream turbulence) I see that the factory distance is about 4" to the start of the inside radius of the 90- I definitely have room constraints with the 4" pipe i will be using (sch 10 304 ss---OD=4. 5")If the radius can be shorter- i can make it fit. It will look odd - the exhaust housing will look like it is attached almost directly to the 4" 90. Hope i'm not making this more confusing-wish i had a way to draw this idea and post -

Jeff

 

[Bob Beauchaine]

Why are you staying with 90's? I've converted my down pipe to 2 45's - much better flow. I used a section of '94 pipe so I could also mount my exhaust brake. My down pipe is wrapped in heat sheilding. The setup works great.

Bob

 

[MMiller]

If you're making a 4" downpipe for your truck how bout making one for me?!? There are lots of kits out for 4 inch exhaust/ with 3inch downpipe, for first gens, but I want 4 inch all the way, and can't find anybody to help!! If you can get the down pipe made and are interested I would pay for you to ship me another one?!?



RU interested??



Michael MillerOo. Oo.

 

[backroad]

ME TOO! AND YES I'M YELLING... .





Thanks,

Backroad... .

 

[banjobob]

Hey guys,

If i can fabricate the downpipe correctly-and have it perform correctly(anything is possible with welder and ingenuity) i would certainly fabricate more. After i get the exhaust system built i will try to post photos of it. Just acquired two 4" chrome turnout stacks tonight-these too will be incorporated into new exhaust( formulas truck has got the little wheels upstairs in my head a turnin!).

 

[dpuckett]

Banjobob,



Count me in for the 4" first gen down pipe as well. I need to get a Pac Brake for one of mine, and may as well get 4" if I can. Which leads to the nest question. Will a 4" downpipe from a 2nd gen truck work on our older ones? I know that a few have done the 3" downpipes from the 2nd genners. If a 4" will work, that would make it MUCH easier to do than going 3- 4". BTW, who sells 4" complete ehaust for 4x4s? May not need it, but the 4x4 has a GN hitch, and the one ton doesnt for now. If I keep the 4x4, I will need the 4", along with PW/ PODs, a PDR HX35-16, and an exhaust brake. I want to pass the PSDs out there, and still be able to stop. If I sell the 4x4, it will go in the 1 ton, along with an ATS 3 pc outfit.



Good luck in getting it done.



Daniel

 

[SnoDawg]

I would be interested in on alsoOo. Oo.

 

[cerberusiam]

There is another option that should work with a bit of welding and bending. The later second gen used a cast 45 on the back of the turbo with a flanged connection. Initial measurements look like that would fit with moving the trans fill tube a bit and possibly cutting and turning the down pipe to match the angles. Dropping a 45 directly back of the turbo looks like it should give enough room to mate a 4" down pipe from a second gen in without a lot of problems. You loose the heat shield so header wrap needs to be used but there is a case for wrapping the turbo and down pipe down to the last bend for better flow characteristics anyway. The turbulence created by not having smooth bends is an unknown but considering the melange of crimps and bends in the stock pipe I wonder whether that makes a difference. I would think the increase from 3" to 4" at the back of the turbo would be an area for concern but it doesn't seem to affect the performance on the newer trucks. Just some more ideas to kick around.

 

[banjobob]

hey guys,

I really appreciate the input and the enthusiasm! I will be working diligently on this design-one drawback is that my truck will be out of commision while R&D is in progress

thanks again, jeff

 

[PPeters]

Put me down for one too when you get it figured outOo. Oo.



Pat

 

[Bob Beauchaine]

The 2nd Gen downpipe is flanged to a cast section that hooks up with the turbo. When I installed my BD exhaust brake this is part of what led us to the 2nd Gen downpipe. I believe that with proper alignment a 4" pipe would easily work and fit in the truck. Heat wrap would be necessary. My setup with the 2nd gen pipe "feels" better and I feel that it breaths better. I list it as one of the small things that have contributed to my HP and TQ numbers.

Bob

 

[CAROLINA CUMMINS]

I'm interested in one too, sounds like a good idea







Steve

 

[jlast]

TTT



I have just completed (almost) my 3. 5" exhaust from downpipe back, I made myself. I have some left over pipe and a few bends to use up. I made numerous measurements to see if I can get a downpipe in there in 3. 5" and it will be tight.



I need to find out where to get the exhaust to turbo flange? does anyone know if someone makes one to go up to 3. 5" pipe? I have to 6" center to center 90's and the flange and adapter to go to 3. 5 would have to be less then 2. 5" long to be able to fit both a non and wastegated housings. Or I have to go to a tighter bend like a 3. 5" center to center 90, that I dont have.



Anyone have other suggestions on maybe how to make the above part please tell me, I have the ablility to make anything i think.



Anyone with pics of the 45 cast housing and 2nd gen downpipe please postup. or any info on any mods done to make it fit?



Didnt nascar mark have a modified 4" downpipe on his truck? not sure but I thought I read it somewhere.



Jlast

 

[M'staedt]

Look here for a picture of a 4" downpipe on a '97 CTD in a '72 pickup chassis:



#ad

 

[skobylenski]

I might be interested in one of these too. Oo. Maybe we can get a "group buy" going. Is it you, banjo, who's making these? What's a final cost going to look like?



Scott

 

[sgriffing]

Originally posted by jlast

TTT



Didnt nascar mark have a modified 4" downpipe on his truck? not sure but I thought I read it somewhere.



Jlast

He had the 4" down pipe because he had a PDR HX-40 on his truck.

With the waste gate, it gets tight in there. It's not a true 90* but it's close. You are right on about the header wrap. There is no room for a heat shield.

 

[nascar mark]

Hey guys, If I was to try and have some custom 4" down pipes made up, would you guys be interested in buying some. I would try to get them fabed so that they go from 3' to 4" right away.

I know 2 different ways to do it, but its a matter of being cost efficient.

I will look at both ways and get back to you.

 

[banjobob]

skobylenski- yes I am in the process of making a 4" downpipe. Cost I am not certain of yet - as my original will be fabbed from 4" ss pipe(future downpipes will be fabbed from 4" ss tube).

nascar mark- have you seen a downpipe fabbed out of stainless?the hardest part is fabbing the stainless flange at the exhaust housing-not impossible though. any input is appreciated