Detroit 2-Cycles in 2017+

[kshansen]

As for starting ease of a 4-71 with N-65's. I know of one that just the other day that had been sitting since April of 2015. Now it was in a semi-heated store room, probably 40-50ºF. Just for kicks I pushed in the go button and despite a somewhat slow crank from a 12 volt battery that had also not been charged in that time, it only took a second or two and was up and running. This is a very low hours engine that last saw a real load on it maybe 20 years ago and even back then it did not get worked hard enough to burn the paint off the exhaust manifold! It will be a shame when it ends up in a scrap trailer some day when company management decides they have no use for it but won't sell it because they want too much money for it!

It started life as a two valve head engine in a NorthWest Crane. When crane was scraped, probably another sad story, it was saved. Then when there was a need for a PTO engine to run a portable crusher we rebuilt it and upgraded to the four valve head, radiator and PTO clutch included along with emergency shut down controls. Got used for a short season then put in storage.

 

[check]

Other factors in cold starting... the non turbo engines had higher compression ratios which helps starting so long as cranking speed is the same. Many I've been around had air starters that spun them over in an instant and no worries about toasting the starter.

 

[RZucker]

Other factors in cold starting... the non turbo engines had higher compression ratios which helps starting so long as cranking speed is the same. Many I've been around had air starters that spun them over in an instant and no worries about toasting the starter.

Yep, 18 to 1 in an N and 16 to 1 in a T.
I'm kind of chuckling over the comments about the lack of lugging ability they had, displacement is the key to torque. If anybody cares to do the math on a 71 series, it comes out to 426ci on a 238HP 6-71, 568ci in a 318HP 8V71, and 852ci in the 475HP 12V71... those HP numbers are without a turbo. How much HP can an 855ci Cummins make without a turbo?... 250. The 12V71 was no slouch for torque in my book. And at 475HP WITHOUT a turbo...? Cummins had to resort to "Old Double Trouble" to match that. And those weren't exactly successful engines.
Personally, my favorite 2 stroke to drive was the 8V92... good power in the 430's and really good starting torque. With the right treatment they could go all the way to 500+ HP easy.

 

[td25c]

Yep, 18 to 1 in an N and 16 to 1 in a T.
I'm kind of chuckling over the comments about the lack of lugging ability they had, displacement is the key to torque. If anybody cares to do the math on a 71 series, it comes out to 426ci on a 238HP 6-71, 568ci in a 318HP 8V71, and 852ci in the 475HP 12V71... those HP numbers are without a turbo. How much HP can an 855ci Cummins make without a turbo?... 250. The 12V71 was no slouch for torque in my book. And at 475HP WITHOUT a turbo...? Cummins had to resort to "Old Double Trouble" to match that. And those weren't exactly successful engines.
Personally, my favorite 2 stroke to drive was the 8V92... good power in the 430's and really good starting torque. With the right treatment they could go all the way to 500+ HP easy.

Good points RZ !

When you consider the cubic inch comparison the Detroit is quite a power house in the package .

Would be interesting to see total production numbers from the beginning in 1938 to present . Imagine it would be a crazy staggering number of engines .

The design is almost 80 years old and still being used . That speaks volumes in itself .:yup

Can any other Diesel engine company lay claim to that long of a run on a series engine ?

 

[Junkyard]

I just read an article that said 3.5 million produced since 1940. Also stated over 500,000 still in use. Seems low to me....

I had talked myself out of that winch truck but this thread has me itching for one. Maybe I'll find an old rig with a 12v71 to build my next service truck out of!

Junkyard

 

[Truck Shop]

Stories are just that in most cases, here are two that I was a part of that are true blue.

When I was working for a repair and towing company in the mid 80's we got a state patrol call for an impound on a semi on I-90 east of Ellensburg Wa.
So the boss and I drove out in a one ton rig just planing on driving it back to the lot. When we got there it was 10:00 PM and the stater was waiting
for us with the subject in the back of the cruiser. Kevin the boss went to tell the cop what we were going to do and I went and looked the truck over
with a flashlight. I came back to the cop car and the rear window was cracked so the arrested driver {who had 11 failures to appear** could hear me.
I said Quote ** Damn that thing is a Hot Rod-buzzin dozen with twin turbos** that driver about came unglued. Screaming at me to be nice to his truck.
It was a 110 sleep KW100 and it did haul A$$.

The other was a guy out of Indio Calif. that had a Mack Superliner with a V-12 built by a marine shop in Long Beach. The color of the truck was black
and it had a name painted on the top front of hood that I cannot repeat. But it truly was the fastest thing on I-5, a real rocket. I also new another
fellow that had a extremely turned up 3408, he admitted he could not run with that Mack. I saw it one time at Biggs Junction I-84 & 97 with the hood
up at the truck stop. It was a mess of turbos and polished tubing under there.

Truck Shop

 

[John C.]

Horsepower is only the ability to accelerate. Torque is what moves loads and the Detroits were never any competition to the comparable horsepower anything. Put a 350 Detroit on flat land and it would outrun any 350 Cummins or Cat. Put the same rig pulling the Rockies or Cascades and there weren't enough gears for the buzzing ones to be in sight when the four strokers cleared the top of the mountain. You had to increase the number of cylinders to get the necessary torque which meant you had to pay the piper for the extra fuel it took to make the same time at the end of the trip.

I enjoyed them when I was young and not paying the bills. I still like listening to them and talking stories of times gone by. People got good at fixing them because there were so many and you had to do it so often. I'm not unhappy that they are being relegated to the past.

 

[Scrub Puller]

Yair . . .

Dunno. They did everything I ever needed. If the world could only have one diesel engine family the 71 series would be it

I once hauled a D9G about four hundred miles with a 6-71 in a Pete. Heavy scrub canopy, angle blade with over the top treepusher, single tine Kelly. Lord knows what I was grossing.

Hot, over forty C and the bitumen was melting. Two rows of eight 8.25-16's on the trailer and the only time we stopped was to change tyres . . . back it off the blacktop unload tractor, chain around tree pusher, lift arse end of trailer, fit spares, rinse and repeat as required. Fun times but that Jimmy never missed a beat, ran up near the red at times but never overheated . . . even if there had been 400hp on tap the limitation was the tyres.

No one here has mentioned they were like a Commer Knocker and, on a hill wouldn't hold you worth a damn. That could be a real issue with the brakes we had at the time.

Cheers.

 

[RayF]

I wonder how many here have heard of or driven the Commer Knockers?

 

[RZucker]

I wonder how many here have heard of or driven the Commer Knockers?

Not me. But I do admit with the exhaust valves opening at the at the top of every piston stroke the Detroits didn't have much retarding capacity without a well adjusted Jacobs brake.

 

[td25c]

I enjoyed them when I was young and not paying the bills. I still like listening to them and talking stories of times gone by. People got good at fixing them because there were so many and you had to do it so often. I'm not unhappy that they are being relegated to the past.

Yeah John , my guess is the military is still keeping them around due to how simple the engine is and it's performance in the past .

That's what got the thread started . Detroit 2-Cycles in 2017 +

Would be a good idea to have new cutting edge equipment with all the electronics & teck to go with it .

An even better idea to keep some " old school " in the fleet that cant be " hacked " by a computer or effected by an electro magnetic pulse .

They will be around for a long time bro .

 

[RZucker]

Horsepower is only the ability to accelerate. Torque is what moves loads and the Detroits were never any competition to the comparable horsepower anything. Put a 350 Detroit on flat land and it would outrun any 350 Cummins or Cat. Put the same rig pulling the Rockies or Cascades and there weren't enough gears for the buzzing ones to be in sight when the four strokers cleared the top of the mountain. You had to increase the number of cylinders to get the necessary torque which meant you had to pay the piper for the extra fuel it took to make the same time at the end of the trip.

I enjoyed them when I was young and not paying the bills. I still like listening to them and talking stories of times gone by. People got good at fixing them because there were so many and you had to do it so often. I'm not unhappy that they are being relegated to the past.

Yeah those Detroits were really troublesome engines (SARC). I don't recall any Detroits pulling headbolt threads, or leaking water under the liners, or melting down pistons. All big issues with Cummins engines in the same day. As far as "horsepower", the FFC's, NTA's, and NTC Cummins all had to be wound tight to get full power too. So... Back in the day there was no clear winner, I've run both an NTC 350 and an 8V71T 350 over Snoqualmie and in "the day" I preferred the Detroit. It pulled better without the heat, and usually heat on the pyro means wasted fuel.

 

[Birken Vogt]

I think the "lack of torque: perceived by many is just a consequence of the bone simple fuel system.

The injector injects so many mm3 per stroke and that is that. At 1400 RPM it is only going to be able to inject 2/3 the fuel as at 2100 RPM so it will theoretically have only 2/3 power at that point. Torque remains relatively constant. No torque rise.

Compare that to a Cummins with PT injection. The fuel meters through the hole mostly independent of engine RPM. So at 1400 RPM the engine is still injecting the same amount of fuel but more on each stroke so torque is rising as the engine lugs down. Horsepower remains relatively constant.

Detroit did have TT (tailored torque) which I don't know if I ever operated one but my understanding is that the "governor" was modified (would have needed larger injectors too) so that it would feed more fuel per stroke as the engine slowed down to mimic the feel of a Cummins or Cat.

I do know that with DDEC there was no rack any more, each injector was electrically fired and thus there was no reason at all for torque to be any different from any other engine as the computer controlled everything. This is what I did drive and I know that lugging down to 1400 was no problem at all but the DDEC 92 series engines may have had other modifications internally so that liner and piston scoring was not such an issue as it was reputed to be on the older ones. I do know that the had the "bypass blower" on this model which meant that when it was up on the turbo the air from the turbo was going straight into the air box and not through the blower any more except what air the blower always moved because it was still there and running.

Also jacket water aftercooling.

 

[RZucker]

I think the "lack of torque: perceived by many is just a consequence of the bone simple fuel system.

The injector injects so many mm3 per stroke and that is that. At 1400 RPM it is only going to be able to inject 2/3 the fuel as at 2100 RPM so it will theoretically have only 2/3 power at that point. Torque remains relatively constant. No torque rise.

Compare that to a Cummins with PT injection. The fuel meters through the hole mostly independent of engine RPM. So at 1400 RPM the engine is still injecting the same amount of fuel but more on each stroke so torque is rising as the engine lugs down. Horsepower remains relatively constant.

Detroit did have TT (tailored torque) which I don't know if I ever operated one but my understanding is that the "governor" was modified (would have needed larger injectors too) so that it would feed more fuel per stroke as the engine slowed down to mimic the feel of a Cummins or Cat.

I do know that with DDEC there was no rack any more, each injector was electrically fired and thus there was no reason at all for torque to be any different from any other engine as the computer controlled everything. This is what I did drive and I know that lugging down to 1400 was no problem at all but the DDEC 92 series engines may have had other modifications internally so that liner and piston scoring was not such an issue as it was reputed to be on the older ones. I do know that the had the "bypass blower" on this model which meant that when it was up on the turbo the air from the turbo was going straight into the air box and not through the blower any more except what air the blower always moved because it was still there and running.

Also jacket water aftercooling.

You hit the nail on the head with the "Tailor Torque" statement. Those were very large injectors and you had to lug the engine to compress the TT springs in the governor to access full fuel at the lower rpms... Ergo what DDC called constant horsepower at differing rpms.
ETA, I worked for one company that had an 8V92 "Fuel Squeezer" that their former mechanic could not tune for whatever reason. So he put a standard LS governor capsule in it and called it good, the "squeezers" had huge injectors meant to run at low speed. This thing ended up well over 500+HP and unless you really trained a driver it ate drive tires and u-joints like crazy. I drove it myself once and with a full legal load on the drivers it would still spin tires in 3rd gear if you jumped on it hard.

 

[td25c]

Yeah those Detroits were really troublesome engines (SARC).

That one made me laugh RZ ! Good points .

We use both Cummins & Detroit engines in the fleet .

Each one has it's place .
http://www.heavytruckforums.com/showthread.php?263-Some-Holmes-750-action&p=2462&viewfull=1#post2462
If anyone don't like it .... Go cry somewhere else ! This is a heavy equipment forum . LOL !

 

[willie59]

I think we can all agree the old Detroit green leaker two strokers are a love/hate relationship. And I think it's fair to say it was a unique engine, hard to compare or be comparable to any other brand 4 stroke diesel. But their unique traits made them an engine of legend. I once got a call from a large corn processing plant in my area, their Whiting Trackmobile was done, 4-53 engine. Sure enough, she was toast, couldn't even get it to fire off with nose candy, and with a Trackmobile being a heavy little plant, couldn't really get it loaded on a trailer without its own power. So, in-frame overhaul on site. Crankshaft was fine, just dropped new pistons and liners in it, rebuilt head, new oil pump, had it back up and running in short order. Even at that time it amazed me how it seemed that engine was designed to be busted apart and put back together right down to the slightest detail. Customer was happy when it roared to life.

 

[check]

One thing I really liked about 71 series Detroits is that I could easily and quickly assess the condition of the rings by pulling the air box covers off and bumping it over until the rings were even with the intake ports on the sleeves. Detroit rings have a line on the wear portion of the rings ( where they contact the sleeves) to facilitate the assessment.
Back in the early 80's when I worked on diesels for a living, there were 2 kinds of diesel mechanics; the kind who mainly worked on Detroits and the kind who mainly worked on everything else. I was the latter type.

 

[td25c]

I think we can all agree the old Detroit green leaker two strokers are a love/hate relationship. And I think it's fair to say it was a unique engine, hard to compare or be comparable to any other brand 4 stroke diesel. But their unique traits made them an engine of legend. I once got a call from a large corn processing plant in my area, their Whiting Trackmobile was done, 4-53 engine. Sure enough, she was toast, couldn't even get it to fire off with nose candy, and with a Trackmobile being a heavy little plant, couldn't really get it loaded on a trailer without its own power. So, in-frame overhaul on site. Crankshaft was fine, just dropped new pistons and liners in it, rebuilt head, new oil pump, had it back up and running in short order. Even at that time it amazed me how it seemed that engine was designed to be busted apart and put back together right down to the slightest detail. Customer was happy when it roared to life.

Well put willie .


We had a similar event as the Trackmobile when the 8- V-71 in the scraper went " ka- bang " . Cleaned all the shrapnel out of the air box , patched a hole in the block & in framed it on job site . We got lucky as the crankshaft was still in good shape .

Always a good feeling to hear them roar back to life after a disaster .

https://www.heavyequipmentforums.com/showthread.php?11965-Wabco-c-pull/page2

 

[Junkyard]

I have a 2005 KW W900L that scattered a C-15. Anybody got a 12v71 laying around... I smell a repower! Wouldn't that be a sight. Well more a sound. Late model truck with a buzzin dozen in it. Sounds just crazy enough to work :drinkup

Junkyard

 

[kshansen]

I have a 2005 KW W900L that scattered a C-15. Anybody got a 12v71 laying around... I smell a repower! Wouldn't that be a sight. Well more a sound. Late model truck with a buzzin dozen in it. Sounds just crazy enough to work :drinkup

Junkyard

Sad thing is a couple years back where I worked we had an R-35 Terex haul truck with a 12V-71 in it. It was a running truck but engine had been let go for too many years and needed some love and care but would still haul a load to the crusher. Might have only needed some injectors and a tune up. Anyhow when the winning bidder came to pick it up after loading it on the trailer they measured the overall height then took a torch and cut the front suspension into! When my boss asked why they did that guy said well we only wanted the Allison Transmission, the rest is going in the scrap bin!