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Twin turbos on a 6.2?

jarheadk5

jarheadk5

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Since my upcoming 6.2 swap is a long-term project, and I DO want to force-feed it eventually, I keep thinking that I should start gathering the stuff to install a turbo while everything's apart. You know, that whole trying-to-think-ahead thing, and not repeating tasks like front clip removal... But I digress.
Anyhoo, my cousin and I were kickin' some ideas around last night waiting for his cousin to show so I could check out the donor truck. One of the ideas was a twin-turbo setup, which of course got the ol' mental hamster wheel to spinnin'. /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif Now I'm no turbo wizard, but I have read just enough to make me dangerous... /forums/images/graemlins/whistling.gif
Sooo, knowing that two smaller turbos can make as much (or more) power as a single big turbo, but without the turbo lag issues... would 2 small turbos (obviously, 2 of the same type), sourced from some import app, work on a 6.2?
Now before anyone says it, I know that this would require some fab work; exhaust manifolds/headers and the intake plumbing probably being the biggest headaches. And I have no idea what apps would have turbos of the appropriate size/flowrate/??. I imagine if I lurked around on some of the import racing sites (racers, not ricers... /forums/images/graemlins/wink.gif) I could probably find some flow info on various import-car turbos.

/forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif

So, is this:
A: just a pipe dream that I should walk away from /forums/images/graemlins/screwy.gif
B: possible, but not worth the hassle/expense on an off-road truck /forums/images/graemlins/dunno.gif
C: an interesting concept that just might turn my humble 6.2L diesel into a tire-shredding, axle-snapping terror /forums/images/graemlins/histerical.gif


I anxiously await opinions/firebombs...
 
Unless you are racing it or doing sled pulls, dont waste your time. If you do go through with it, head studs and some sort of aftermarket head gaskets as well as low compression pistons are a must.
 
I like it.

The good thing with turbo-ing a diesel is you don't have to worry about fuel mixture issues, just EGT's which you'd have a guage for anyways.

I have a set of H1 headers that would probably be easy enough to modify, and the intake issue would'nt be to hard to do. I think the tough part might be plumbing two downpipes.

As for sizes, beats the hell out of me. Maybe the turbo's they used on the typhoon or GN would work. Run a pair of them...

Biggest issue is not to overboost the engine and cause a catastrphic failure. Stock they have cast pistons and stuff. The later 6.5 TD's ran (marginally) better pistons with oil spray un the underside to help keep them cool. I think the weak point would be in the bottom end on a used motor.

I can see 220 and 500 at the wheels with a twin turbo though...which would shred tires nicely i'd think.

Rene
 
Peter Bierman from the Netherlands, a www.thedieselpage.com member, installed twin turbos on his 6.2L Blazer. It was quite a chore. He fabricated his own exhaust manifolds from scratch, and mounted one turbo on each side. He also lowered the compression ratio by milling off the tops of the pistons a bit. Performed really well, although he just recently blew his head gaskets. I don't know if he's finished yet, but he was also installing a 300hp Peninsular fuel injection system.

You can read the article if you order this book. My advice: become a member and you can read all these articles when they get posted online! That's one of the greatest benefits of being a DP member.

Anyway, a twin-turbo project is not for the faint-hearted. It would be cool, though!

Casey
 
[ QUOTE ]
Since my upcoming 6.2 swap is a long-term project, and I DO want to force-feed it eventually, I keep thinking that I should start gathering the stuff to install a turbo while everything's apart. You know, that whole trying-to-think-ahead thing, and not repeating tasks like front clip removal... But I digress.
Anyhoo, my cousin and I were kickin' some ideas around last night waiting for his cousin to show so I could check out the donor truck. One of the ideas was a twin-turbo setup, which of course got the ol' mental hamster wheel to spinnin'. /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif Now I'm no turbo wizard, but I have read just enough to make me dangerous... /forums/images/graemlins/whistling.gif
Sooo, knowing that two smaller turbos can make as much (or more) power as a single big turbo, but without the turbo lag issues... would 2 small turbos (obviously, 2 of the same type), sourced from some import app, work on a 6.2?
Now before anyone says it, I know that this would require some fab work; exhaust manifolds/headers and the intake plumbing probably being the biggest headaches. And I have no idea what apps would have turbos of the appropriate size/flowrate/??. I imagine if I lurked around on some of the import racing sites (racers, not ricers... /forums/images/graemlins/wink.gif) I could probably find some flow info on various import-car turbos.

/forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif

So, is this:
A: just a pipe dream that I should walk away from /forums/images/graemlins/screwy.gif
B: possible, but not worth the hassle/expense on an off-road truck /forums/images/graemlins/dunno.gif
C: an interesting concept that just might turn my humble 6.2L diesel into a tire-shredding, axle-snapping terror /forums/images/graemlins/histerical.gif


I anxiously await opinions/firebombs...

[/ QUOTE ]

I say if you have the time, go for it.
I have a couple of engines that are rebuildable and I want to rebuild one to have 2 turbos on, and it will be a while before I get it finished but I just want to do it.
I also have the perfect truck to recieve it too, I am building it this winter.
 
Just a bit of clarification...
I'm not looking to "bomb" this motor, or make super-high boost pressure. I'm just thinking, based on stuff I've read before, that a twin-turbo setup with small turbos will have better throttle response and less turbo lag at low RPM's. Is my thought process on this correct?
For me, the point of the exercise would be better throttle response and power at low RPM's for offroading, with the fuel economy inherent in a diesel. If I tow anything with the truck, it won't be real heavy; 3-4K lbs. max.
 
Go with a correctly sized wastegated turbo instead of twins, you will be much happier and a lot less work.
 
Even a NA 6.2 has exceptional throttle response and off idle torque. IMO a turbo on a 6.2 is not needed for wheeling, especially if you're crawling.

Even a quick spooling turbo wouldn't be making much boost at 1000-1500 rpm anyways.

Rene
 
[ QUOTE ]
Just a bit of clarification...
I'm not looking to "bomb" this motor, or make super-high boost pressure. I'm just thinking, based on stuff I've read before, that a twin-turbo setup with small turbos will have better throttle response and less turbo lag at low RPM's. Is my thought process on this correct?
For me, the point of the exercise would be better throttle response and power at low RPM's for offroading, with the fuel economy inherent in a diesel. If I tow anything with the truck, it won't be real heavy; 3-4K lbs. max.

[/ QUOTE ]

I didn't think you wanted to bomb it, I am not either.
But if it's for rock crawling you won't need that, if for a faster kind of wheeling you might.
I am building a multipurpose off road and on road vehicle that I can drive to the trails and will be for dunes, snow, basically fast trails.
For rocks I have my inline six that gets me 415 ft lbs of torque stock.
And as for someone's suggestion to build it with on wastegated turbo, I guess you weren't looking for the right way but a different way and maybe even a cheaper way, right?
/forums/images/graemlins/waytogo.gif
 
A smaller wastegated turbo will spool up quick and make decent boost at the high end without too much cost or trouble. I wish the turbo on my crew cab was an ATS with a wastegate so it would spool quicker. I would be more than willing to give up a few pounds at high rpm to gain some low end torque.
 
[ QUOTE ]
I am building a multipurpose off road and on road vehicle that I can drive to the trails

[/ QUOTE ]

Precisely what I'm doing. I don't have the luxury of a tow vehicle or a trailer, so it has to be streetable. Some of my wheeling will be done at altitude (Paragon in PA - don't know the exact alt. but it sure ain't sea level), and I've read the NA 6.2 gets to be a dog at altitude.
 
Moab is anywhere from 4000 to 6000 feet above sea level, and I only noticed a small drop in power when we were there. I live right on the west coast and maybe 30 feet above sea level, so I'm used to the max power my 6.2 will make...

It's not as gutless as some people will lead you to believe, although having more with a turbo would be cool.

Rene
 
[ QUOTE ]
A smaller wastegated turbo will spool up quick and make decent boost at the high end without too much cost or trouble. I wish the turbo on my crew cab was an ATS with a wastegate so it would spool quicker. I would be more than willing to give up a few pounds at high rpm to gain some low end torque.

[/ QUOTE ]

Hey my burb has the ATS turbo on it, are they all wastegated?
I haven't had the chance to look at it yet since it wasn't running when I got it and now I will be looking into fixing it.
Where is the wastegate usually on those?
is it somewhere at the bottom?
 
[ QUOTE ]
Moab is anywhere from 4000 to 6000 feet above sea level, and I only noticed a small drop in power when we were there. I live right on the west coast and maybe 30 feet above sea level, so I'm used to the max power my 6.2 will make...

It's not as gutless as some people will lead you to believe, although having more with a turbo would be cool.

[/ QUOTE ]

Really? Huh... I've heard that NA diesels in general lose quite a bit of power at altitude, but no personal experience of it. Guess the power drop isn't as bad as some people make it out to be.

I drove M1008/9's around a bunch while in the Corps, so I know the NA 6.2 isn't totally gutless. If it was, I certainly wouldn't waste my time and $$ swapping out my TBI small-block for it.
As far as "having more with a turbo would be cool" goes... Too much is just enough, right? /forums/images/graemlins/woot.gif /forums/images/graemlins/woot.gif
 
[ QUOTE ]
A smaller wastegated turbo will spool up quick and make decent boost at the high end without too much cost or trouble. I wish the turbo on my crew cab was an ATS with a wastegate so it would spool quicker. I would be more than willing to give up a few pounds at high rpm to gain some low end torque.

[/ QUOTE ]

So, where would one look to find one of these ATS wastegated turbos? Would this be taken from a donor vehicle, or a purchase from ATS? Do you have a part # or an application to look for in a yard?
 
The turbo set-up on the 6.5 TD's is a wastegated turbo. I believe it's a GM8 and you see them relatively cheap on ebay now and then...usually as an assembly.

I really don't know how those turbo's stack up against the ATS. The banks I've heard only starts making boost in the upper rpm's which seems useless to me.

Rene
 
I believe all ATS turbos as well as the 6.5 turbos are wastegated. Im not sure exactly where it is on the turbine housing, but it should not be too hard to find.
 
You would have to call up ATS and see if you can still get turbos from them, and as was already mentioned the 6.5 turbos would probably work well.
 
[ QUOTE ]
The banks I've heard only starts making boost in the upper rpm's which seems useless to me.

[/ QUOTE ]

That's EXACTLY why I'm thinking small twins would be a better, more cost-effective all-around setup than a bigger single for what I want to do. The smaller turbines would require less hot-side energy to get spooled up and start providing manifold pressure. Faster spool-up at a lower RPM = /forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif

After I do some more research on import boards and The Diesel Page, I think I'm gonna give this a shot. It's a long-term project anyway so why not... As long as I monitor upstream EGT's and boost pressure real closely (along with the other stuff) I suppose I can avoid meltdowns.
 
Like I already said, a properly sized wastegated turbo would be good enough for what you are using it for. You forgot that the response of the turbo has as much to do with the energy in the exhaust as does the size/efficiency of the turbo. 6.2s just do not flow enough fuel to get a turbo to spool up instantly like say a bombed Cummins or OTR truck diesels. You stick two turbos on there and I dont think the 6.2 will have enough exhaust energy to spool them both up quickly without turning up the fuel to a point that may damage the engine. You put a small wastegated turbo on and it will spool rather quickly and do a decent job as higher rpm. This is all just a theory that twins will not work well, so do not take what I say as gospel, but I do have a decent amount of experience with this, so I kinda know what I am talking about.
 
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