Diesel Place banner

Twin Turbo on my 6.5

119K views 190 replies 77 participants last post by  654L80 
#1 · (Edited)
I told you I would do it...;) I just picked up all the 10 feet of 304 stainless steel pipe I will need to build my... oh wait, I haven't told you yet:eek:: I'm dumping my exhaust manifolds, and building stainless steel headers for a twin turbo setup on my 6.5l diesel.

I drove to the supplier and ordered up all the 304 stainless steel 90's and 45's I should need, they cost around $130 CDN, and will be in tomorrow. I got the 10' of 304 stainless steel pipe for $100 CDN, prices were cheap because we have a place here that specializes in alloys. All piping is schedule 10S, and a secret size.:cool:

I still have to get the 304 stainless steel plate for the flanges, I'll probably just have the machine shop cut it out of some of their stock.

I'm going to buy another GM-8 turbocharger too, and another Turbo-Master as well. I'm going to try and set it up so that I can just order two 3" down pipes, and they will fit both sides, I don't know if it can be done, but I'll try.
 
#2 ·
let me be the first to say:

sweet.

keep us updated with the pics!!! lookin forward to this
 
#3 ·
Sounds like a deivious plan in the making :)
 
#5 ·
May breathe a little easier, but our turbos already put out
as much as a 6.5 can handle - I wouldn't go thru that much
trouble, but I'll enjoy watching :D
 
#6 ·
what are you going to do about fuel
 
#7 ·
Sounds great cant wait to see how it looks. I have similar plans in mind when i get out of school
 
#8 ·
While this would be and awesome looking engine bay especially with your intake, the only way you could have this work with two GM-8 turbos would be to either rev the motor up to 5K+ which is what Heath does on their salf flat truck. But unfortunetly the motor would be lazy down low in comparision to a mild modded 6.5 now. The turbine sections of the GM turbos is too big for 190ci+ per side and will make for a slow boost up. I don't think an array of components for the BW/IHI turbos are available to make a hybrid.

But you could change to Garrett turbos and have two custom turbos built using a T3/T4 hybrid and have wicked low end response and be able to further the top end efficiency using well selected T4 compressor sections and keep the RPM's to a realistic level by running matched T3 turbine sections.
 
#27 ·
While this would be and awesome looking engine bay especially with your intake, the only way you could have this work with two GM-8 turbos would be to either rev the motor up to 5K+ which is what Heath does on their salf flat truck. But unfortunetly the motor would be lazy down low in comparision to a mild modded 6.5 now. The turbine sections of the GM turbos is too big for 190ci+ per side and will make for a slow boost up. I don't think an array of components for the BW/IHI turbos are available to make a hybrid.

But you could change to Garrett turbos and have two custom turbos built using a T3/T4 hybrid and have wicked low end response and be able to further the top end efficiency using well selected T4 compressor sections and keep the RPM's to a realistic level by running matched T3 turbine sections.
He wasnt saying there will be too much backpressure, but not enough, which I don't think that is true at all. The GM-8 runs just fine up to maybe 10PSI boost with low enough backpressure, but anything more than PSI requires a much greater backpressure and makes it very inefficient. You just have to adjust the wastegate actuator to whatever boost amount you want, and you have two, so you dont need 10PSI out of each, so with 5PSI each you'll get all the air needed at much less backpressure making it much more efficient.

Heath uses some special different turbos, not GMXs and he tunes his specifically for top speed, and his gearing is for top speed, so there is no way to make comparison, except his huge fuel economy jump using low backpressure twin turbo.
 
#9 ·
Who cares what turbo's he starts with, turbos can always be swapped.
 
#13 · (Edited)
Agreed, once I start working again, maybe next week because a new pipeline is going in, I'll see about better suited turbos.

I'm no turbo expert, but I'm sure I can find some that will match nicely. A question I have though, what about the turbo flanges, I know there is T3/T4, should I make mine able to accept both?

I think two turbos flow more air, with less back pressure... plus, true duals!
 
#11 ·
Peninsular Diesel sells a 400hp twin turbo motor. I seriously thought about it before I pulled the trigger on my 300hp model. They probably have a nice manifold set-up that you could buy and easily install yourself. Everything in their shop looks top notch. I believe that had a twin turbo model in the customer waiting area. It looked awesome! Not sure about longevity with the 6.5 bottom end though....

Jake
 
#12 ·
one question why dont you run 2 smaller better flowing turbos that will divide the boost equally instead of a parrel system this way the motor breathes way better with little restriction with get spool up time. just my 2cents because the basics of a diesel are simple just a big air pump more air in easily and more air out easily equals efficency witch in turn equals power. plus you dont have to worry about grenading that motor
 
#14 ·
sunbirds had some nice small turbines in em ... two small snails will spool faster .. lemm know how it turns out .. maybe a nice van mod for latter in the express' life
 
#15 ·
inlinesix, I knew you had somethin up your sleeve when you started building that intake manifold! :D:D:D

Like Jake said above. Call Peninsular to see what they have for a manifold, maybe ask them what turbos they ran too! The two GM-8s should work very well IMO and you can weld/fabricate well. Hopefully everything will be straightforward.

That truck is gonna be wicked!!!

If the turbo setup ends up as well as your intake, it will be simply amazing!

Subscribed.

Post plenty of pics of your progress.

I would be honored to share some advice/info, if needed.
 
#17 ·
With your fabrication capabilities, I'd decide on your initially planned turbo size (T3 flange will allow you lots of options so you can find a size the 6.5 can spool up to useful boost at a low enough rpm threshold to be fun to drive.) My thought is you can optimize the collector/flange transition smoothly for 1 size flange, or compromise to fit "in btwn" 2 alternate sizes.

If you decide to try T4 later, chop off the flange end & weld in a transition that goes smoothly out to T4.

Burns Stainless has an impressive offering of supplies for this type of fabrication. Not cheap, but dang they've got some cool stuff: slick merge collectors, oval shaped tubing, etc. Check out their website - the tech section has a good article on turbo headers - lots of great exhaust fab tech info.

You might inquire w/ Heath to see if the header setup they had fabbed included some type of bracing to help support the turbo(s) weight. There's a fair amount of weight to be supported and lots of temp related expansion/contraction. Probably worth visualizing how things might move as they heat up & consider what needs to flex & what should be held more rigidly.

Many of the highly turbocharged 4 cyl aftermarket headers have cracking problems. Not certain how much of that is related to choosing too thin stainless tubing due to cost considerations. Also most have no bracing to help support turbo weight/movement.

I have a neighbor that's TIG'd up a number of successful 4 cyl turbo headers. I think he uses the weld "El"s mentioned in "Maximum Boost" by Corky Bell. If memory serves, the weld els are common fab supplies in the oil industry & maybe hydraulics. I'll try to get some specifics from my neighbor & let you know.
 
#18 · (Edited)
I was planning on making a brace of some kind, to keep tension off the exhaust bolts. Sch 10S stainless pipe is 0.109" thick, I highly doubt it will crack, since I got all the pipe and such at the same place that supplies the chemical plants. I don't know what the difference between weld "EL"s and pipe elbows are, since you can get short radius, long radius, and 3R ect. I'm going to arc weld these up probably, I can do a better job arc welding stainless than I can TIG welding it anyways.

I can get some pretty crazy bends out of this pipe, just by heating it a certain way, stainless has some crazy contraction and expansion rates.

I'm thinking this will cost $500 all said and done.
 
#21 ·
Can you guys imagine the whistle that motor will make??? That would be worth it by itself!!! Throw dual DB2 pumps on there and you will be set for fuel! :D
 
  • Like
Reactions: BogieWheelz
#23 · (Edited)
Glad to hear this Will, I look forward to seeing some pics.
You just like to use a welder don't you?:D
 
#24 ·
Make sure you study other twin turbo setups. I think all of them include a bank equalizer pipe that runs between the post turbo pressurized plumbing on each bank as it enters the manifold.
 
#26 ·
You might also want to consider including plumbing in external wastegates. When you're designing all this from scratch, you could incorporate wastegate bypass passages that are vastly superior to the turbulent way the OEM wastegates reintroduce bypass exhaust into the stream.

Racers tend to run "external dumps" meaning they simply vent the 'gate's bypass exhaust to open air instead of merging back with the exhaust system. This avoids the additional turbulence in the exh system, but sounds pretty crude.

All these things add lots of cost. Just mentioning these things as design considerations are free to think about & I hate it when I hear a great idea right after my fabrication is completed:eek:

If you have a chance to check out Corky Bell's book "Maximum Boost", I suspect you'll want a copy. It's been the best overall turbo systems info source I've found. Relatively unbiased & helps separate solid theory from myth.
 
#28 ·
I am planning to twin my 6.5 eventually. The stock turbo manifold has a major design flaw in the the back two cylinders can expel their gas down into the crossover just as easily as it can find it's way to the turbo. If you use headers, I guarantee it will spool 2 GM8s, they have tiny turbine housings. My plan was to modify two stock turbo manifolds and block the x-over ports, effectively giving you a 4 into 1 manifold for each head. Just cutoff the x-over port and get someone who can weld cast put a plate over the opening. The manifold locates the turbo flange in the middle of your head, so on the drivers side the turbo geometry could be tweaked to clear everything. Building a twin turbo is the easy part, finding enough fuel to burn is the hard part. Stanadyne lists max power at 20hp/cylinder for the jcode DB2 pump, 25hp/cylinder for 4911DB2 pumps and 30hp/cylinder for the DS4 EFI and 40hp/cylinder for the DB4pump. All these numbers have been surpassed before though, Peninsular's 400HP 6.5 has a DB4 that makes 50HP/cylinder. Sounds like we need to get a hold of some DB4s :)
 
#30 · (Edited)
I am planning to twin my 6.5 eventually. The stock turbo manifold has a major design flaw in the the back two cylinders can expel their gas down into the crossover just as easily as it can find it's way to the turbo. If you use headers, I guarantee it will spool 2 GM8s, they have tiny turbine housings. My plan was to modify two stock turbo manifolds and block the x-over ports, effectively giving you a 4 into 1 manifold for each head. Just cutoff the x-over port and get someone who can weld cast put a plate over the opening. The manifold locates the turbo flange in the middle of your head, so on the drivers side the turbo geometry could be tweaked to clear everything. Building a twin turbo is the easy part, finding enough fuel to burn is the hard part. Stanadyne lists max power at 20hp/cylinder for the jcode DB2 pump, 25hp/cylinder for 4911DB2 pumps and 30hp/cylinder for the DS4 EFI and 40hp/cylinder for the DB4pump. All these numbers have been surpassed before though, Peninsular's 400HP 6.5 has a DB4 that makes 50HP/cylinder. Sounds like we need to get a hold of some DB4s :)
You don't even need more fuel to take advantage of twins on these.
Just having the same amount of air at less pressure would be huge. That's why I've been tossing around the idea for a while. Very happy to see a regular Joe Schmo 6.5'er who has the skills and resources do it. If you notice, most large engines use the same set-up. Just a couple examples are the Cat C32 and Detroit 12V71T.
 
#29 ·
whats stopping people from putting twin DB4's on these engines. Electronics?
 
#31 ·
whats stopping people from putting twin DB4's on these engines. Electronics?
There is a guy with twin DB2's on his 6.5TD that is in a Massey Fergussen tractor. I think it would be too much of a headache to run twin DB4's with all the electronics.
 
#32 ·
well twin DB4's would be sweet if someone figured out how to do it. im sure its possible
 
#33 ·
The DB4 is mechanical just like the DB2.

The DS4 is the one with the electronics.

Plenty of fuel can be had out of a single DB4. The DB4 mounting pattern is exactly 180 degrees from what a DS4 or DB2 is. The front cover would have to be modded, -or buy one from pen-marine.

As far as having two DS pumps, -the only thing worse than having a PMD would be having TWO of them!! :D
 
#35 ·
As far as having two DS pumps, -the only thing worse than having a PMD would be having TWO of them!! :D
Ha ha, exactly right!

How does the DB4 compare to the DS4 and DB2 in output?
Is it basically a mechanical version of the DS4?
I am unclear on them.......
 
#34 ·
yeah all these letters and numbers i typed the wrong pump name. as far as two DS4 pumps and two PMDs im sure it could be figured out eventually after plenty of headaches. plus you could relocate so they wouldnt burn up
 
#36 · (Edited)
it says the DS4 is rated at 30 horespower per cylinder were the DB4 is rated at 40 horsepower so i figure the DB4 can flow more fuel but i dont know for sure
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top