I want to fab up a new crossover pipe and i want some input on what would be better.. 2" sch40 or 2 3/8" erw .065wall... whats better thick or thin? thanks.

The Heath Diesel crossover is 2.25". I put one on my brother's truck and think it is as big as you would want. If I remember correctly, it is slightly bigger than the manifold outlets. Also, any bigger and you might have trouble with the flares.


It was heavy pipe. I don't think there would be any advantage to thin pipe but thick will last longer.

Well i was thinkin more along the lines of what would allow for faster exhaust gasses thick or thin, but sch40 to .065 is like 1/16 so im not sure it will be that big of a diff...oh and is that heath 2.25 ID or OD?

I don't remember if it was ID or OD. If you won't have it mandrel bent, you might want to use a little bigger pipe but you might have a problem with the flares. I seem to remember that the heath one might have gone slightly smaller right at the end for it. (but maybe not)


People insulate them to retain the exhaust heat. I would think that thicker would keep the heat longer and thinner would transfer the heat quicker.

I think a bigger crossover is great but the turbo on the 6.5 is a restriction itself. The only real answer is one turbo for each exhaust side. This would mean fabricating a new intake to accomodate both compressors. the turboside exhaust manifold should fit the drivers side, but I havn't yet verified this myself. If it fits, I'm going to modify it as the yellow line illistrates(both sides would need to be modified).


http://www.dieselplace.com/forum/uploads/1CD_exhaustcut.jpg


This is about where the other turbo might sit.


http://www.dieselplace.com/forum/uploads/DC3_newturbo.jpg


Edited by: quantum mechanic

http://www.dieselplace.com/forum/uploads/7AF_crossover.jpg


This is the stock 2" crossover. I decieded to re-create the crossover into a better flowing unit by cutting off the collectors and welding in a bigger, less crimped 2 3/4" pipe. I used the stock exhaust off of a ws6 that I had salvaged last year. It has a lot of nice mandrel bends and I just have to eyeball it and cut it out.


http://www.dieselplace.com/forum/uploads/5BE_crossovers.jpg


The pieces are coming together well and only a little grinding to remove the burs from cutting and a little time to double check the angles and clearence before finish welding. Total time about one hour.


http://www.dieselplace.com/forum/uploads/1E9_crossover3.jpg


The end result will be less backpressure. I will have a local muffler shop make one for me next week with 2 3/4" pipe and new collectors, for comparisson. Edited by: quantum mechanic

QM,


How far along are you in this, still some time to do some mods???


2.5" out another 2.5" with 2.75" inbetween probably won't do much for back pressure, but the mandrel bends will improve flow over factory bends. have you seen Doc Lees adapter over at TD Page, bolts right at the outlet of the mifold that is where I'd start the transition to 2.75" sooner the better to start the transition IMO, that said; again I don't know how much reduction in back pressure you will achieve as the bottleneck is the turbo/wastgate.


This is a guess on my part, you might even be reducing response by lowering gas pressure to spin the turbo, reduction of turbo outlet gas pressure is beneficial I'm not sure lowering supply to turbo is a benefit, probably a point where the right balance of supply vs BP is , I don't know where that is in the 6.5; maybe JD can weigh in on this one.

I am a diesel fanatic,


I got out in the pouring rain and bolted it up this morning ( made it yesterday). I agree with the 2 1/2" collector being a restriction, but my project was to see what I could do with scap( once the crossover was off it was scrap). It cost me the price of a few electrodes, the fuel the welder used and a little 110v from the line to cut the pipe. pennies really. I am about to test it on a grocery run.


http://www.dieselplace.com/forum/uploads/277_crosspipes.jpg I think it will flow.


Edited by: quantum mechanic

QM,


Good on ya; necessity being mother of many inventions, also economics being mother of: "It ain't purty but it works",


Good luck, let us know how it turns outEdited by: Turbine Doc

I drove it about 200 miles today. I think it helps in the top end, and I had to use the 4wd to even out the torque in the mud, I was having trouble giving it a "little" throttle. It is also louder starting at about 1000 rpm. all in all it's been a great learning experience.


I decieded to make the next one with 3" mandrel bend pipe instead of 2 3/4"to see if there is any benefit to more flow and use 2 1/2" to 3" collectors. It will go on the '96.


I noticed that the bullydog downpipe I used was a 3" collector welded on a mandrel bent 3" pipe. I decieded that I'm going to buy a 4" mandrel bent pipe and weld a 3" to 4" transition collector on it. I estimate this will cost under $50. expect a DIY Downpipe post soon.Edited by: quantum mechanic

quantum;





YOUR a productive fellow!! http://www.dieselplace.com/forum/smileys/Clap.gif


More Power to you man. I hope your projects all work out for you!!http://www.dieselplace.com/forum/smileys/Approve.gif

For your consideration -


Flow dynamics dictate matching pipe i.d. to manifold outlet diameter, matching pipe i.d. to opposite manifold inlet diameter.


Crossover pipe to exhaust port matching is as important as port matching in the intake path.


Secret is smooth flowing gradual bends, no crimping, no ripples, no furrows.


No increase, then decrease in diameter - this causes turbulence, increases back-pressure, reduces flow. Reduces heat energy.


Dumping into a large diameter exhaust-tailpipe system does not create problems - long as no increase-decrease stepping is used.Edited by: gmctd