Increasing the power of the Detroit Diesel 6-71

[wg4t50]

Just how fast are you willing to afford ? Its just a $$$$$ thing.
Local wacko balanced his 8V-92, cleaned up heads, port matched exhaust manifolds, 145 injectors, unknown turbo that make massive boost, Governor at 2800 rpm, in a Senicrusier.
How bad do you want the big power ?
Dave M

[Audiomaker]

Just how fast are you willing to afford ? Its just a $$$$$ thing.
Local wacko balanced his 8V-92, cleaned up heads, port matched exhaust manifolds, 145 injectors, unknown turbo that make massive boost, Governor at 2800 rpm, in a Senicrusier.
How bad do you want the big power ?
Dave M

Sitting in my driveway I could care less.   Having to pee for 2 hours on a 6% and I'm ready to sell the wheels.

Browsing the net, I'm not the first guy to roll along wishing the DD had a little more go, and I doubt I'll be the last. 
Nobody expects these things to haul butt up a hill, and in fact, like most drivers pulling large trailers, or heavy loads, I expect to come to a crawl at times and throw the flashers on.
There is a point though where it borders on not being drivable.  It's the point where you've moved out of the slow lane onto the shoulder and the 80,000lb-ers are having to exit the shoulder back onto the road to get around you.   I'd say dropping under 10mph on a 6% or so.

Best guess... from moving a DT466 from 220 to 250hp, and moving a CAT 3126 from 250hp to 300hp, and having towed 45' trailers loaded with each... I think this thing needs about 350 to get in the game, and 375 to make it pleasant.
That's still under the 400 or 450 danger zones for this engine from what I'm understanding, and it doesn't have to be a dummy light engine (ie...I don't mind watching a EGT on the panel).  Yeah... about 350-375 in the 900-1000lb/ft range would work, and be worth a few mod's without going too crazy (including mod's that preserve the motor at that rating).

Luvrbus pointed out a housing with a different A/R that might be better suited since he implied it worked better at the top end...which is currently where I'm always at now.  2000rpm on the hill, 2000 rpm @ 60mph...  just turn it on and put it at 2000rpm until you get there really.
A tad more air and maybe some injectors sounds like a good solution.  I can't yet bring myself to more injector without more air (I'm still fighting that in my head).
Still no word on water/methanol injection for the DD.  I have some questions about that into the manufacturers regarding any problems with that system on a 2 stroke.
Like I said before, maybe I'll blow this one up in a year or two messing around.  If I still like the truck at that point, maybe a balanced and blueprinted hot motor might go in?  Gotta see where life takes ya.

[wg4t50]

Agree on slow & needing to pee !   However as I get the picture, your vehicle is suffering from lack of a mechanic, nothing in good order will run the speed your talking about.  Hell a 318 DDC with 73,280 lbs runs 28 mph on mountains, that is slow, not " under 10 mph".
Don't think you can wish your way to running better, find a shop that likes DDC engines and geterdone, you will be happier.  Forget the 425 hp outa that critter, that is a dream.
Dave M

[Audiomaker]

Agree on slow & needing to pee !   However as I get the picture, your vehicle is suffering from lack of a mechanic, nothing in good order will run the speed your talking about.  Hell a 318 DDC with 73,280 lbs runs 28 mph on mountains, that is slow, not " under 10 mph".
Don't think you can wish your way to running better, find a shop that likes DDC engines and geterdone, you will be happier.  Forget the 425 hp outa that critter, that is a dream.
Dave M

Yep... will get in touch with "Don" asap.   I might be headed through his area soon.

Don't think I ever said anything about 425hp tho'.   375?  350?

And yeah... 10mph up the grapevine outta Los Angeles.   I think there's a 7% grade in there somewhere.  Floored at 2000rpm in whatever gear would keep me moving.  Kept my speed most of the time with the loaded trailers.  You always know the heavy trucks, but yeah, they're pulling 80k with the same fight that I'm pulling 34k.  Never overheated though... I'll say that.

[wg4t50]

I don't mean that to sound like a whine, but as an observation.  With so many years of service, I was expecting to see at least a few "kits" or "packages" available on the open market.  Rebuild kits with stronger components that let you get that 425 with some longevity...etc.
It's just something I wanted to mention.


Sean

I think is where I got the idea about the 425 hp dream ?
Agree, get it to a known mechanic indeed.
good luck
Dave M

[Audiomaker]

I think is where I got the idea about the 425 hp dream ?
Agree, get it to a known mechanic indeed.
good luck
Dave M

Ah yes.  Sorry, that was what I was expecting to find on the market since such things are available for other engines.  It was just leading to the idea that for such a popular engine, there doesn't seem to be a lot available pre packaged for this one.
As for my actual idea of what makes the truck serviceable... about 50-75 more than what it already has... whether that be by fixing it, or adding to it, and I only mention those numbers to get feedback on whether that is a big custom job to get, or just a couple tweaks (I'm trying to prepare myself and my budget).

Cheers!

[eagle19952]

Here's my take:
If you do twelve things at once you'll never know where the improvement came from.
Get/check a tune up, that'll set your baseline: valves and injectors settings
Be sure and short the injectors while your there, listen for gross difference...no difference then you found a weak cyl.< (injector, valve or rings/piston or all of the above)
Go drive it.
Set the governor up another 2-250 rpm no load.
Drive it.
Still not happy twist the gov to 2325 max.
If there is no remarkable/noticeable improvement Re-gear it
Having said that I wouldn't even touch the motor until you've told us what the final gear ratio is.
If it's as low as I think it is your wasting your time until you re-gear.
Then after you know the gearing, start thinking about the turbo.
AND BEFORE ALL THAT...well consider that a 1983 model motor just might need rebuilt, My 1978 is no virgin and as much as it sounds like that motor has spent against the governor I'm willing to bet it needs some TLC.
I have never seem a DD motor that did not have at least the oversize rod bearings stamped some where on a heavy metal coupon that would stick out like a sore thumb.(Every rebuild I have done or saw has it)
If it ain't there That motor has to be tired there is no way that it can't be.
what are the gear ratio.

[Audiomaker]

Here's my take:
If you do twelve things at once you'll never know where the improvement came from.
Get/check a tune up, that'll set your baseline: valves and injectors settings
Be sure and short the injectors while your there, listen for gross difference...no difference then you found a weak cyl.< (injector, valve or rings/piston or all of the above)
Go drive it.
Set the governor up another 2-250 rpm no load.
Drive it.
Still not happy twist the gov to 2325 max.
If there is no remarkable/noticeable improvement Re-gear it
Having said that I wouldn't even touch the motor until you've told us what the final gear ratio is.
If it's as low as I think it is your wasting your time until you re-gear.
Then after you know the gearing, start thinking about the turbo.
AND BEFORE ALL THAT...well consider that a 1983 model motor just might need rebuilt, My 1978 is no virgin and as much as it sounds like that motor has spent against the governor I'm willing to bet it needs some TLC.
I have never seem a DD motor that did not have at least the oversize rod bearings stamped some where on a heavy metal coupon that would stick out like a sore thumb.(Every rebuild I have done or saw has it)
If it ain't there That motor has to be tired there is no way that it can't be.
what are the gear ratio.

Eagle,   I am in complete agreement, and as others have said, the first step should be to get it to a wise DD specialist.
The problem is that I'm moving and I have at least another month involved in completing it. Add to this that there's a time limit to get my shop and stuff moved because the reason I'm moving its that I lost a lawsuit (over a commercial lease), and they are taking my house I paid cash for in full out from under me (ugh).   

Just so everyone knows, I'm basically living in this thing parked outside of the house I'm trying to move from... in preparation... and I'm trying to also covert the very basics of this truck to live in because that's all I'll have time for before the sherif comes.
To make matters worse, my "house" is an old school, and it's 33,000sqft including a 8000sqft machine shop, and I'm doing it by myself...which is really slow going.

Being as forthcoming as I can, I agree with everyone here that I should get this truck to a mechanic to find a baseline, but all I can do for the moment is read as much as I can, and ask you guys questions.

I'm getting a lot of great information here.  I'm figuring out about where my truck should be... about what can be done to it simply... about what my expectations should be...etc.  I'm very grateful.  If nothing else, at least when I get to that mechanic I will have a vague understanding of what he's telling me. 

Anyway, as for the rebuild, I was told it was rebuilt in 2000.  They did not have paperwork. I bought it from a mega-million dollar medical imaging company who really didn't seem to have too much interest in the sale of this truck.  So little interest in fact that it doesn't seem like they'd lie about the rebuild.  Everything else they described to me about the truck before picking it up in person has been better... in fact much better than described so I wouldn't be amazed to find that rebuild tag under there somewhere.
Also, the truck doesn't feel like the engine is tired.  My DT466 was a tired motor...smoked...vibrated randomly..etc.  This starts right up and is pretty clean when running.  I dunno.

I just found another tag...

The transmission is a MT-654CR
The tag also has the engine model (6L-71TA), so after all that Sherlocking, it was right there.  I feel like a boob.  Just overwhelmed folks.
No gearing information on that one, but I'll hunt around some more in the daytime when I can.

And again... I'm sorry for asking all the questions about propane and methanol and such.  It doesn't mean that I'm going to rush out an do that stuff without following the correct path first.  I'm just curious and wanting to learn everything I can as soon as I can.

Regards
Sean

[Audiomaker]

In the meantime... maybe this will help...

Around 1900-2000 @ 60.   Almost can hit 70 on a flat given cool air, 10 minutes tryin', and an RPM of about 2100ish.

?

[Iceni John]

In the meantime... maybe this will help...

Around 1900-2000 @ 60.   Almost can hit 70 on a flat given cool air, 10 minutes tryin', and an RPM of about 2100ish.

?

That sounds like 4.1 axles.   I get 67 MPH at 2100 RPM with a 4.1 and 12R22.5 tires.   At least your transmission ratios are slightly closer than a regular MT transmission's.

Get that lead outa there.   You need to put your bruck on a diet.

John

[Audiomaker]

That sounds like 4.1 axles.   I get 67 MPH at 2100 RPM with a 4.1 and 12R22.5 tires.   At least your transmission ratios are slightly closer than a regular MT transmission's.

Get that lead outa there.   You need to put your bruck on a diet.

John

I will.   I am going to need to install another door soon to create an inverter compartment, and at that point I'll be sawing into the side of the rig and will get to see how "stuck" this stuff is (this is encapsulated lead sheeting used by hospitals and such...reported to be safe).

I think I'll have to approach it a section at a time from the interior.  It's all riveted...yay.  Will have to drill out the rivets in a panel to open it...uninstall electrics and such that run over it... pry it out or whatever, cut insulation and reinstall.
If I just took off with a drill right now I probably wouldn't have much of a rig left to live in, so I'll either do it a panel at a time, or wait until I have a shop again.
Emphasizing the positive, it's a nice resounding "thud" to close a 150lb entry door   Feels very solid.

[wg4t50]

Should have mentioned about the 28 mph on mtn with the 318, that is exactly why I installed the 12V-71 in the MC7, never found a mountain after that.
Never been a happier kid with clothes on
Dave M

[TomC]

To get really crazy, you could pull the lay down 6-71TA and install two 4-71's end to end with a HT740 (shorter then your transmission). Then you could safely have 400hp and 1200lb/ft torque.

Some will say that doesn't work as exampled by the first drive train in the PD4501's. But you have to remember, the Scenicruiser was running the two engines side by side with a hydraulic coupler. You'd be running the engines end to end drive shaft attached as one engine.

Detroit during WWII made a quad 6-71 marine engine. It was rated at 900hp max and 650hp continuous. What was unique was that you could throw the clutch, turn off one engine while the other three were still running. Good Luck, TomC

[wg4t50]

Agree, the DDC combinations are near endless and beautiful setups, have sperience with a twin 6-71 common gearbox with Twin Disk clutch setup, could run the generator on one while servicing the other. The fun was matching them for hp, exhaust temp etc. Another good old days memory, maybe the beginning of my DDC joys.
Dave M

[Audiomaker]

To get really crazy, you could pull the lay down 6-71TA and install two 4-71's end to end with a HT740 (shorter then your transmission). Then you could safely have 400hp and 1200lb/ft torque.

Some will say that doesn't work as exampled by the first drive train in the PD4501's. But you have to remember, the Scenicruiser was running the two engines side by side with a hydraulic coupler. You'd be running the engines end to end drive shaft attached as one engine.

Detroit during WWII made a quad 6-71 marine engine. It was rated at 900hp max and 650hp continuous. What was unique was that you could throw the clutch, turn off one engine while the other three were still running. Good Luck, TomC

Tranny change?  Uh oh.... let me guess... MT-645CR is only rated to 286hp? (1 extra)...lol. 

If this gets any worse, I'm gonna build an island in my galley (which is right over the motor), and stand a CAT up in there.

Designers really need to stop under powering commercial trucks.  I've been through this before.