My 4" exhaust with custom rear housing for turbo.

[67_C-30]

It has been covered on here and other diesel forums before that the factory exhaust housing on the rear of the GM-X turbos is restrictive and could be the cause of some of the back pressure associated with them. After some measuring, I found that the inside of the casting measures a touch under 2.600" at the outlet and is more restricted than that on the inside the where the 90 degree bend is. It seems to me that this would have no choice but limit the effect of bigger exhaust. I decided to build a custom system that will be 4" from the turbine housing back. I machined the flange at work on the CNC, and I'm building the pipe from pre-bent 90 and 45 degree pipes that I will have to cut and butt-weld to the straight lengths. I am going to have to run outside of the frame rail due to the position of the turbo and the narrower frame on these year trucks vs the newer ones that the 6.5TD were designed for. I'm planning on turning it out right before the rear wheels on the passenger side. I know this style turbo is small and is still not going to be as efficient as a bigger one. However, maybe this will make it a little more efficient and lower EGT's a little. Either way, it should sound good! I'm just hoping it won't cause any significant lag, but I'm think as small as it is, it won't be much if any.


Here's a few mock-up shots.

http://i226.photobucket.com/albums/dd85/67_C-30/tdturbohousing.jpg

http://i226.photobucket.com/albums/dd85/67_C-30/tdturbohousing4.jpg

http://i226.photobucket.com/albums/dd85/67_C-30/tdturbohousing2.jpg

http://i226.photobucket.com/albums/dd85/67_C-30/tdturbohousing3.jpg

[6.5 Detroit Diesel]

What year truck is it? And do you still have the plans.:D Or are willing to replicate and sell? I have been trying to figure out a way to get a bit better flow, and look to put a bigger downpipe in, even if it means trimming the inner fender. I already have stacks on the truck, so a bit more exhaust work isn't out of the question.

[6.5 Detroit Diesel]

Never mind on year of the truck, I just saw your name.

[trbankii]

Just have to say that I love the Detroit Diesel green engine! :cool: Looks sharp.

I could also be interested in a flange if you decide to produce them.

[Robyn]

Its all about airflow and lots of it.

Looking good my friend :D

Robyn

[67_C-30]

Thanks!

I finally got all my mounting issues and clearancing done, and its bolted in the truck. I've got to modify the radiator support to accept the radiator and then plumb the intercooler and I can fire it up. I will get some video and soundclips as soon as she is running.

http://i226.photobucket.com/albums/dd85/67_C-30/TDmounted8.jpg?t=1222649844


http://i226.photobucket.com/albums/dd85/67_C-30/TDmounted-1.jpg

http://i226.photobucket.com/albums/dd85/67_C-30/TDmounted9.jpg

[ercaduceus]

It looks great. I'd be interested in such a modification but the wastegate flapper (not sure on technical name) and actuator shaft are built into the GM-8 turndown.

[arveetek]

Looking good!

I might warn you about dumping the exhaust in front of the rear wheels. I had my truck set up that way at one time, and I had a terrible time keeping the wheels clean! All the diesel soot was deposited directly onto the wheels and looked awful. When I built my 4" system, I took the time to have the exhaust go up over the axle and then exit behind the right rear wheel.

If you don't mind sooty, black wheels, then it's no problem. I just thought I'd give you a heads up on that if you hadn't already considered it.

Casey

[rhsub]

Your engine looks good but I would clean the paint from the bimetal spring in the front of the clutch fan, those clutches are slow enough to react without insulating the spring with paint
Good luck
Ron

[More Power]

Good job on the turbo mods!

GM employed what is known as a "banjo" exhaust exit on their 6.5 turbos. According to what I've read in various engineering books on turbo diesels, they indicate a banjo shaped housing is a little more efficient that a round section when making a 90 degree turn.

Since you're doing this, you will likely be very interested in a new article coming this 10/15 on 6.5 turbochargers.... Your ingenuity and machining skills in creating an exhaust exit could be a big help... ;)

Jim

[67_C-30]

Looking good!

I might warn you about dumping the exhaust in front of the rear wheels. I had my truck set up that way at one time, and I had a terrible time keeping the wheels clean! All the diesel soot was deposited directly onto the wheels and looked awful. When I built my 4" system, I took the time to have the exhaust go up over the axle and then exit behind the right rear wheel.

If you don't mind sooty, black wheels, then it's no problem. I just thought I'd give you a heads up on that if you hadn't already considered it.

Casey




Your engine looks good but I would clean the paint from the bimetal spring in the front of the clutch fan, those clutches are slow enough to react without insulating the spring with paint
Good luck
Ron

Great info and suggestion from both of you guys. I'll defintely get the paint off that spring, and I'll do a little more thinking on my exhaust outlet. My dilemma is that I am going to have to run it outside the frame, and I'm not sure I have enough room to get over the rearend with the spring in the way, but I haven't looked at it that closely. My buddies are begging me to do a stack, but I'm not sure if I like them or not. I do have a set of 19.5"
wheels and tires that I may use on it, and the big wheels and stack would have the big rig kinda look, but I'm just not sure if I want to go that route.

[67_C-30]

Good job on the turbo mods!

GM employed what is known as a "banjo" exhaust exit on their 6.5 turbos. According to what I've read in various engineering books on turbo diesels, they indicate a banjo shaped housing is a little more efficient that a round section when making a 90 degree turn.

Since you're doing this, you will likely be very interested in a new article coming this 10/15 on 6.5 turbochargers.... Your ingenuity and machining skills in creating an exhaust exit could be a big help... ;)

Jim

That's interesting on the bango exit, I didn't know that. I did have to flatten the tubing on the end to weld it to the flange, but the 90 degree part is still round. Even with the tubing being flattened a little, and a little indention to clear one of the bolt holes, it is much bigger everywhere than the factory piece. I finished it up today, and I'll get some closeup shots of it for you tomorrow hopefully. I chose the pipe I used because it has a 5" inside radius on the 90 degree bend. The pics don't do it justice, but this thing is a longer than it looks. I'm positive it would be not clear the firewall on a GMT-400 truck that this turbo was designed for. However, flow dynamics are tricky. You would think dual 2" pipes would outflow a single 3", but they do not. I'll just have to compare it versus the stock housing and DP to see what difference it makes. I'd like to compare to the stock housing and an aftermarket 3" DP as well, to see what the difference would be between the two since this the most common upgrade above stock.

If you need anything for the project you mentioned, I'll help anyway I can. When we slow down a little at work, I'm going to try to make several more of the flanges.

[67_C-30]

I got the pipe fitted and welded top the flange. It took quite a bit of persuasion to make it fit all the way around due to odd shape of rear exit of the turbo. The opening is slightly bigger than the factory opening so there is no overhang. The ended up being a little over 4.5" at it widest point and around 3.5" at its smallest. It is still WAY bigger than the inside of the cast. The last shot shows how wide open the exit is. It makes a nice smooth transistion down for a 90 degree turn.

http://i226.photobucket.com/albums/dd85/67_C-30/tdturbohousing5.jpg

http://i226.photobucket.com/albums/dd85/67_C-30/tdturbohousing6.jpg

http://i226.photobucket.com/albums/dd85/67_C-30/tdturbohousing7.jpg

http://i226.photobucket.com/albums/dd85/67_C-30/tdturbohousing8.jpg

[arveetek]

Looks great!

Casey

[DP]

The banjo's I've seen are big, about as big in diameter as the turbine housing. Check this out:

http://img.photobucket.com/albums/v14/SaabTuner/BanjoCloseup1.jpg

Scanned from old HP book "Turbochargers", 1978. The object is to dump the exhaust into a larger area to get the exhaust to change from a swirl to turbulent flow. On higher flow gas engines it seems popular to keep the wastegate flow from mucking up the business as well. Once the flow is broken up, you can actually go back down in diameter a bit. On gas engines with higher exhaust temps, you'll see some benefits from stepping the diameter up as you get farther away from the engine. As the gases cool, they slow down and need more room. I suspect the same principle holds true with diesels under a full load, otherwise the exhaust is so cold it's got very little energy.

I'm looking forward to the turbo info later this month.

[More Power]

Any entrepreneurial member here who wants to fabricate a new turbo outlet pipe like that needed for the Holset turbocharger discussed in the new October article on turbochargers (http://www.thedieselpageforums.com/tdpforum/showthread.php?p=244505), we’ll help you with a free ad for 6 months.... ;)

Actually, I have an idea for a new downpipe that could make it easier...

Jim

[67_C-30]

Well, after a nearly 2 year year hiatus, I FINALLY got the 6.2 running in my dually.:o The 4" housing sounds great and really seems to help free up the turbo (at least it whines way louder). I have ran it with the factory housing with a foot long section of a factory 6.5 downpipe to compare, and there's a big difference. The poppy, choppy sound that the factory stuff makes is eliminated with the 4" piece. The 4" is very deep and powerful sounding. Since I have made this video, I have put the radiator on the truck and drove it around my land, and it really sounds awesome! The turbo screams with pretty much any throttle under a load, and sounds wicked at the shift points. Here's a little sampling of it. I couldn't run it but a minute because I didn't have the radiator in place at that time. I will post more videos after I get the front clip back on the truck and get back on the road.

http://www.youtube.com/watch?v=nXhvZP9wryk (http://<a href=)

[67_C-30]

Any entrepreneurial member here who wants to fabricate a new turbo outlet pipe like that needed for the Holset turbocharger discussed in the new October article on turbochargers (http://www.thedieselpageforums.com/tdpforum/showthread.php?p=244505), we’ll help you with a free ad for 6 months.... ;)

Actually, I have an idea for a new downpipe that could make it easier...

Jim

Sorry Jim, I didn't see this. I had some stuff come up right I after I originally posted this (READ: career change due to this great job market:rolleyes:) that postponed my plans for a while.