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Author Topic: DD two stroke engines  (Read 5179 times)
Hank
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« on: March 21, 2008, 10:58:42 AM »

Iím curious why the 2 stroke engines gained such popularity in the transit sector. Was it because GM was a major producer of buses for so long and all other manufactures (MCI, Eagle, Prevost) just figured they should use them too? Was it a size consideration (shorter block)? How did Detroit Diesel get such a foothold in the marine sector? Another thing that doesnít make sense to me is that 2 stroke engines typically get around 300,000 miles before needing some level of overhaul whereas some 4 stroke diesels can get twice that if not more before an overhaul-so why would an OEM spec their equipment with an engine that has a known lifespan of at least half of other similarly powered diesels? It doesnít appear that itís any cheaper to overhaul a 2 stroke! Were they just that much more reliable? Also, 2 strokes use a lot of oil compared to a 4 stroke which make it more expensive to run and requires more PM. Wouldn't that deter OEM's too? Questions, questions, questions! Iím interested in a little history lesson on Detroit Dieselís 2 stokers or a link to any relevant websites if anyone knows.
Thanks,
Hank
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tekebird
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« Reply #1 on: March 21, 2008, 11:28:39 AM »

Hank,

back in the 50's when this all started....maybe even late 40's the DD was one of the most reliable powerplants out there.  and as a two stroke they are stone age simple unliuke a  four stroke.

I am sure others on the board have alot more in depth history combined with tech data.

I suspect that early 4 strokes didn;t get any better mileage (TBO) than a 2 stroke, and I suspect used similar ammounts of oil.......now with that said, a properlymaintained Detroit does not have to use any significant ammount of oil...perhaps a few Qts ever few thousand miles.

just as with people saying the 6-71 or other two stroke is low on power....I think most would find that they are just running tired engines.......there are few out there that have low mileage or new DD crate engines to compare to, and by the nature of the beast your average conversion owner does not know diddly about the history and prior maint of his particular powerplant...other than what the prior owner told them.

I would hazzard a guess that the 71 series engine is the ost produced and has the highest logevity as a group whole of any other powerplant produced for  commercial service.

someone a while back posted a number of 71's that are still plying the roaqds and waterways as well as running pumps, mills generators etc.

It was quite impressive and likely an underestimate.
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TomC
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« Reply #2 on: March 21, 2008, 11:44:31 AM »

Detroit Diesel, originally GM Diesel, brought out their first engine in 1938-just in time for Gray Marine to introduce them into the landing craft during WWII.  When introduced, they were considerable smaller than any 4 stroke engine since turbocharging was just in its' infancy, being used primarily in expensive aircraft engines and primarily by the military.  The 6-71 was so versitile, on a larger landing craft that needed twin 600hp engines, rather than creating a huge engine room for two giant in line 8 cylinder train engines, they just hooked four 6-71's together in a bull gear, so that 8 relatively cheap engines achieved the same result as the very expensive and heavy train engine.  Then too the engines one at a time could be serviced while under way.  The 6-71 also has seen service laid down under the bus floor on both Crown and Gillig school buses, and stood vertically for space saving generators on oil rigs.
Even in the 80's when the 92 series were being used, they were still around 400lb lighter than the closest Caterpillar or Cummins engines, and got very close to the same mileage.  Oil consumption was accepted (I had one and got 2200miles per gallon of oil).  On my 8V-92TA, there was a definite schedule of maintenance you needed to do.  Every 100,000 miles run the injection rack; at 200,000 miles, roll in new bearings; at 300,000 miles overhaul the blower, turbo and injectors; at 400,000 miles roll in new bearings; at 500,000 miles usually a complete overhaul.  At this time, both Cummins and Caterpillar were getting about 250,000 to 400,000 miles before overhaul.  Only recently with the advent of electronic fuel injection with air to air intercooling have the engines been able to go towards one million miles before overhaul.
Because of the small size of the 2 stroke, most buses were using them.  Since Detroit stopped making the 2 strokes in 1998, the bus companies had no choice but to go to the 4 stroker.  The engines that are very close to the 2 strokes in size, weight and power are the Detroit Series 50; Cummins ISL, ISM; Caterpillar C9, C12, C13; and Volvo 13 liter.  Buses have to be modified for the Cummins ISX, Caterpillar C15, C16; Detroit Series 60, DD15.  
Personally, if you're thinking of changing out your engine, I would not consider the 2 strokes anymore-they are getting harder to find mechanics that know how to work on them (and they do have their own quirks).  I think the either the Detroit Series 50, Cummins ISL at 400hp, or the Cummins ISM are good engines to switch with.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #3 on: March 21, 2008, 12:43:45 PM »

Hank,

Gotta agree with Doug on this..

The 71 series Detroit Diesel was released for public use in 1938. It had been in development from somewhere around 1930, and had been in Military testing for most of those years.
My ex-father in law was a tank commander during WWII and had been in the testing program at Ft. Knox from the early to mid 30's.
He told me about running the MkII and III tanks at 27MPH with the gas engines as delivered from the factory, (GMC and Continental mostly). He told me they loved to put the 4 and 6 71's through their paces compared to the gas engines because they would continue to to run as long as there was no blockage in the air intake or the fuel system.

I've been a diesel mechanic for as many years as I've been able to read and worked with them since before that, (our trucks and logging equipment ran mostly Detroits and Cummins'). The Detroit doesn't leak or burn oil as a habit, it burns and leaks oil because someone didn't build it correctly or take care of it after it was built.
My 6-71 (2-valve) topped Jellico Mtn. at the Tn-Ky border at a speed of 45 mph, better than many of the MCI 102DL's and E models here at the bus company I am parked at. Most of those with the Cat and Cummins and Detroit 60 series engines can only get up that hill at 38-41 mph.
Since we left South Carolina in July 2007, we've put well over 3,000 miles on our bus. It has an old, tired, engine with one injector that doesn't belong. We average 9.8 to 13.67 mpg for fuel and have only added 1 gallon of oil in that time. The oil was the result of a leak in the air compressor.
300,000 miles? I ran a 1974 KW K-100E with a RTOO9610/Detroit 318 turned up to 360HP/2450RPM for well over 500,000 miles before I had to rebuild... it dropped a valve. My average load was 88,0000 lbs with many exceeding 200,000 pounds.
I never had a starting problem even at -40į(using preheaters and ether, of course), A lot of the loads I hauled were on the dirtiest roads in North America.. the haul road to the Alaska Pipeline and one you have heard of recently... the Ice Road in Canada.
Comparatively, I've had a few newer trucks with Cummins NTC BCIV 400HP, 470HP and one at 625HP that would eat oil from the day I bought them and go through massive amounts of fuel.
I also had a few Cat 3406's that were heavy and sucked when it came to fuel, but would pass up anything else I had on the road. these weren't high HP engines, just standard 325-470HP engines. they were good with oil usage though, a couple of them would never use even a cup of oil between oil changes.
Detroit 2Strokes are great for certain usages especially in bus service... One reason is that the 2 stroke can be run either clockwise or counterclockwise. This means that the engine can be turned sideways, run backwards and deliver all the power needed to move a load of passengers and freight, without the need of a reverser gear on the transmission.
In marine service the DD2stroke is many times put in tandem .. one being Clockwise and one being counterclockwise. This keeps the torque from tearing the hull apart. Even the large Pusher boats and Navy YTB's used the Detroit for motive power.. A few Destroyer Escorts were even outfitted with a series of Detroit 6-278's. 30 knots ain't nothing to sneeze at.

One other reason the Detroit was so popular is that the other engine makers, ie Cummins, Perkins, Mack and some that don't even exist anymore couldn't even come close to the power and reliability and longevity of the DD. Many of the 1950's diesel engines from Cummins were only rated at 150-170HP. It wasn't until the mid to late 50's that Cummins even got past the 200HP mark.

You also need to understand that the DD is (or was) the world leader in innovation. Some of the marine versions of the 71 series 6 cylinders were putting out well over 500HP with a life expectancy of many years.
Cummins tried to compete with it's 903V and 903VT but couldn't match the life span. Truth be told though... in a combat situation, those 903's would work circles around a 8V71, considering that some of them had a battle setting at 1100HP, too bad the Cummins engine would die after a week of that kind of power.

Another thought to put to you is that the largest and most fuel efficient engine in the world is a 2 stroke, derived directly from the DD 1930's design. Here's a shot of it:

http://people.bath.ac.uk/ccsshb/12cyl/

http://k4viz.com/12-Cylinder.html

For fun:
http://gcaptain.com/maritime/blog/the-wartsila-sulzer-super-engine/

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DrivingMissLazy
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« Reply #4 on: March 21, 2008, 12:57:24 PM »

Back in the heyday of the engine I do not believe that the cost of the oil used was even a consideration to most users. Probably less than 1$ per gallon. Hardly can buy a cup of coffee for that nowadays.

Back then I would check my automobile oil level at each fuel stop. Now it is not even checked except when time to change it.

Richard
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« Reply #5 on: March 21, 2008, 01:13:31 PM »

Just a couple of things that I am familiar with. The DD had unit injectors so the engine would always get the bus home, even with one or two bad injectors. All the four strokes with injector pumps were dead on the side of the road with any pump trouble.

However, the biggest reason for their popularity was repair cost. Because of the standardization of parts for the whole 71 series they mass produced parts and sold them cheaply. They had a deal with MCI (prior to Penske) that let me buy DD engine parts below the local DD dealer's cost.
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« Reply #6 on: March 21, 2008, 01:34:16 PM »

In the past I have read that the Detroit Diesel was used because it was the only engine that would put out enough heat to heat the bus in the cold weather.  The cost of fuel wasn't a problem, because it was cheap.  I read this in a artical in the bus trader.  I was the history of busses, can't find it now but maybe someone else can add some more to it.
Now all buses have to have heat othere than the engine to keep the people warm.
Jack
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« Reply #7 on: March 21, 2008, 01:44:51 PM »

No, no and NO!  While the above answers/reasons are very good and complete, we all know the REAL REASON why the 2-stroke Detroits were soosss successful.  It's because they sounded soossss... BITCHIN'!  Smiley Smiley Smiley
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« Reply #8 on: March 21, 2008, 02:52:03 PM »

Along with all of the reasons already mentioned, a DD will START! We had a '54 Autocar with a 170 Cummins. That was the precursor to the 220, which was the precursor to the 250, 335, 400 etc.

I remember building a fire under that miserable Cummins  & using 2 battery chargers & 2 guys to get it started. .... One to pull the compression release and one to try to start the truck.  And the 2 chargers? One for each 6 volt battery bank. Remember, those old engines started on 12V and ran on 6. Can you say "Parallel Switch" ? Another miserable piece of equipment!

My first 671  earned me a lot of ridicule until Dad and I both got ready to leave out one frosty 15 degree morning. I shoved a little ether football in the starter cup, & fired up that old 671 while Dad was building his first fire.

When he caught up to me at Le Hi TruckStop, I had already eaten and had 2 hours sleep. He never ran down my DD again.

I also replaced one hole in a 8V71 in the rest area between Gainesville and Atlanta GA. Try that with a Cummins.

Sorry, I tend to ramble..........

TOM
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« Reply #9 on: March 21, 2008, 03:08:43 PM »

One more reason: Incredibly smoooooth! Lots and lots of firing pulses meant from idle, to full governed speed, a comfortable ride for the passengers.
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« Reply #10 on: March 21, 2008, 07:30:57 PM »

I don't know guys......Six miles from here is a 35 year old self employed truck/diesel mechanic with more work than he and one other guy can handle. He loves Detroits. He has repowered some wheel loaders with rebuilt detroits. They had Cat 3208 or who knows what in them. He has an Oliver farm tractor that he put a 6V92 in thats got huge injectors and is putting out about 700 horse. He competes with it locally in tractor pulls. He runs the rack on that engine each time he pulls with it.

He used to work for a contractor that had lots of old Detroit powered equipment and learned from the "old" mechanics how to fix Detroits.

So there are still some guys out there; maybe those of us in central Minnesota are just lucky?
Fred
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« Reply #11 on: March 21, 2008, 08:39:38 PM »

It has been very interesting reading these posts, a lot of really good information that I will archive.

I love my 671, I love the smoothness and sound of it but I wish it had more lugging power.

For a big truck I prefer the Cummins because of its lugging power and ability to idle for a week with no problem.

Otherwise I prefer my 671.
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« Reply #12 on: March 21, 2008, 11:17:00 PM »

Gus and all others that are running non turbocharged 2 stroke engines.  I can say without a shadow of a doubt that turbocharging and air to air intercooling a 2 stroke really wakes up the engine.  My 8V-71 went from 300hp and 800lb/ft torque to 375hp and 1125lb/ft torque and without smoke at full throttle-big difference in performance-about the same fuel mileage.  Good Luck, TomC
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« Reply #13 on: March 22, 2008, 07:02:51 PM »

Dallas...an exception to what you wrote on the VT903, (VT 90-Nothing LOL) was that a trucking company I worked for in the 80's and 90's (For 15 years) Thomas Produce, later Thomas Transport, Greensboro, NC bought a bunch in the lates 70's early 80's.  Cummins told them for every one they brought in without an overhaul in 1,000,000 miles...they would give them a new one!  After what I think was 7 new ones, Cummins said, "Look, we have to stop this!"  (We ran west coast, team, we could put a million on in just over 4 years!)
If that engine did not ever run hot, and if the oil was changed regularly...you coundn't stop them!
(Of course when it saw a hill...it jumped into high range reverse! Grin

Most folks I have talked to that had them in their boats love 'em!

Jack
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« Reply #14 on: March 22, 2008, 07:08:27 PM »

I'm with Tom on turbo charging.
I turboed my 4-71 and it makes a very noticeable improvement. I now go up the hills one gear higher, (5 speed Spicer). No more smoke either.
The 71 series DD is by far and by all measures the best diesel engine ever produced, just like the Courier 96 is the best looking bus ever built... Ha, ha!
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« Reply #15 on: March 22, 2008, 09:59:16 PM »

Tom,

I would love to turbo my 671. I asked Don about this and as I remember the cost was about half what I have in the bus!!   

I'm an old man, I may not be able to travel in my 4104 very many more years.

I doubt that I would ever get my money back for that investment and I'm not in much of a hurry anyway!
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« Reply #16 on: March 22, 2008, 10:20:27 PM »

I agree that a turbo would be a nice upgrade.  I don't think it is on my real list at this point though.  Wouldn't it require a bunch of extra cooling capacity also?  I think that, when I get to it, my first attempt at a power upgrade will be propane injection.
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« Reply #17 on: March 26, 2008, 09:58:30 AM »

A couple of reasons why I turbo'd.  When we took a trip to Arizona a couple of years ago and went through Flagstaff (7,000ft) to Grand Canyon (6,000ft), because I had N65 injectors, it would smoke with full throttle.  In this day and age, that's not acceptable in my book. Also, the power was down quite a bit.  While that wasn't a problem with not pulling my car on that trip, if I were to pull my car and went to Colorado-I'm just afraid I could stall out on one of the big hills there.  The power of the 8V-71NA wasn't a big deal with me-I never minded going up the hills at 30mph.
I had Don Fairchild turbo the engine.  I had an air to air intercooler made that is in front of my radiator.  Then Don installed an early 12.7 liter Series 60 turbo with waste gate to keep the boost down to about 15psi since I didn't change the pistons (which were two piece with proper rings). With the extra heat, I had the radiator enlarged from a 5 row straight fin to 6 row serpentine fin, added a auxiliary trans cooler with thermostatically operated electric fan (can turn it on continuous also), changed the air cleaner from a 6" to 7" opening, changed the stuffed up muffler to a turbo muffler, cut vents into the back engine door, and added 15 misters to the front of the radiator running off my house water system.  Alot of modifications, but man what a difference in performance with no smoking at altitude except when first starting out from a signal.  Still the same 5-6 mpg, but that's a function of 4.56 rear ratio and the poor aerodynamics inherent to my bus (the old sign in front juts out to create an effective air dam).  But, I cruise at 1800rpm which is 58mph or 2100rpm is 67mph.  I can top out at 76 mph at 2400rpm.  Just a point-still a whole lot easier than trying to install a completely different engine into the bus.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Dallas
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« Reply #18 on: March 26, 2008, 10:57:49 AM »

Jack,

I made that same mistake in the 80's.. I bought a White "Road Commode" from a local Cummins dealer. They promised me that the engine would perform way past my expectations, and if I had a problem, they would take care of it.. at no cost to me, other than labor.
I explained to them that my loads ran in excess of 150K lbs. many times and that I needed to have confidence in my engine. They said, No Problem, if, after 200,000 miles you have problems, we'll install any Cummins engine you want, as long as your transmission and drive train is rated for it.
After a month, they replaced the engine.
After 3 months they replaced the engine again.
After 8 months, they said, "We'll make you a deal"
The deal was, they put in a Cummins BC II at 375HP, change out the transmission and rear gears, and warrantee the truck as new.
They couldn't handle having to pay a wrecker to come haul me in when the engine trashed out on me by swallowing a valve or even just having one haul me up a hill.

Dallas...an exception to what you wrote on the VT903, (VT 90-Nothing LOL) was that a trucking company I worked for in the 80's and 90's (For 15 years) Thomas Produce, later Thomas Transport, Greensboro, NC bought a bunch in the lates 70's early 80's.  Cummins told them for every one they brought in without an overhaul in 1,000,000 miles...they would give them a new one!  After what I think was 7 new ones, Cummins said, "Look, we have to stop this!"  (We ran west coast, team, we could put a million on in just over 4 years!)
If that engine did not ever run hot, and if the oil was changed regularly...you coundn't stop them!
(Of course when it saw a hill...it jumped into high range reverse! Grin

Most folks I have talked to that had them in their boats love 'em!

Jack
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JeffsMagicBus
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« Reply #19 on: March 26, 2008, 12:11:18 PM »

                           SCREAMIN' JIMMY!
  I Don't Condone Speeding But Sometimes You Have To Just Go With The Flow...
 All I Can Say Is My Non Turbo 8V-71 Only Has About 318 Horses I Think It Is And I Can Pass ANYTHING I Want To No Matter How Many Horses They Have. The 1,000 Mile Trip Bringing Her Back Home Was Quiet Interesting With All Those Big Rigs Pulling Up Beside Us Just Trying To Pass Us. I Had All My Bays Full Of Parts And They Would Get Me On The Downhill Side But I'm Not One To Go Hammering It Downhill Either! Uphill's A Different Story!
 Once When I Was Asleep In The Seat Behind The Driver's Seat, While My Friend Frankie Was Driving, I Thought I Was Still Driving And That I Had Her Kind Of Wound Out And That I Should Let Up On The Acclerator But It Didn't Let Up When I Lifted My Foot Up! I Mean I Tried Letting Up On It A Couple Of Times Until It Startled Me, Or Scared Me, Awake! All This Time I Was Hearing These Obnoxious Whining And Whistling Noises... I Looked Up To See Those Big Rigs Hammering Down On Us While We're Just Minding Our Own Business In The Middle Lane. Turbochargers Whistling On The Right, Superchargers Whining On The Left. It Was Kind Of Weird Seeing Their Hoods Even With The Bottom Of The Windows And We Were Crossing The Bridge Into Memphis To Top It Off! Man What A Sight Seeing Memphis Lit Up At Night And You Should Have Seen The Panaramic View Through The Whole Right Side Of The Bus! Needless To Say, The Hoods Weren't There Long Buddy! I Thought They Were Going To Blow Both Their Rigs As They Were Wound Out. And Remember Kids... Don't Try This At Home!
 Let's Just Say A Professional Driver On A Closed Course Could Cruise At About 83-85 In My Crusader.
  And It Was Not Designed To Get Any Kind Of Gas Mileage So That's Irrelivent! I Think It Was Originally Designed In The Mid To Late 30's. That Says It All! Why's It Still Around? Cause You Have To KILL Them To Get Rid Of Them! And There IS Absolutely Nothing That Compares To The Sound Of A Screamin' Jimmy! There's Been More Than One Kind Of Unidentified Flying Object Coming Out Of Roswell...
                                                             
                        Take Care,
                                        Jeff
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