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Tech Editor's DeskProjects, papers, writings, thoughts, musings of our technical editor Joe Padavano. To begin with, he will be making threads and can approve posts to it if he wishes. This can be changed in the future if it does not work out well.
An ebay seller has several cool old GM training posters listed. This one supposedly shows the difference between a two-stroke and four-stroke diesel. Why does each type have the same number of strokes?
Yeah, I can see the differences after lengthy study, but seriously, this may be one of the worst examples of a comparison chart I've ever seen.
Unknown, airing a tire, spraying bugs, lifting a piano, & sweeping.....All while on fire!
Unknown = intake (breathing in)
Airing a tire = compression
Spraying (bugs?) = injection
Lifting a piano = power stroke
Sweeping = exhaust (and scavanging on the two-stroke)
The GM Detroit Diesels are semi-two stroke. The poster loosely describes the Cleveland Diesel-Winton-EMC-EMD uniflow scavenge design starting in 1922 which became the EMC-EMD 567 locomotive prime mover which did then evolve just before WWII into the Detroit Diesel designs we now with the first being the 6-71. It does take two revolutions of the crankshaft to complete one cycle. If you wish to place blame for the demise of the steam locomotive in American railroading, this is the one that did it.
While the Electro-Motive Corporation wiki overview is pretty well detailed the Detroit Diesel wiki overview seems to contain omissions of critical historic detail too numerous to mention. One of the best most successful designs of internal combustion engines ever.
Last edited by coldwar; June 3rd, 2016 at 06:47 AM.
Reason: clarification
This was the history making 1934 application of the engine discussed here in 12 cyl format, actually 'distillate' fueled, not exactly a diesel. Uses standard automotive Pennzoil oil as seen. My Dad has the Lionel model of this unit trainset form his youth, it is restored in his office on a shelf now, he is 86. We were not allowed to play with that one when I was a kid.
I don't know the exact difference right now between the distillate fueled compression ignition engines and those later which were classed as diesel fuel engines when diesel fuel was then specifically and universally formulated for the job, without fuel pre-heating. I have the GM book trainees used and will look for it. My loose recollection of it is the nearly standard application of diesel fuel injection which came in with the third rocker arm per cylinder with later versions of these engines, I do not beleive yet in place with the Winton variant seen in the video.
A Diesel engine, like Joe says, is a compression engine; more specifically, it runs on the Diesel thermodynamic cycle, which is different from Otto and Atkinson cycle engines (gasoline and hybrids, respectively) of today. I think the debate over terms is between a Diesel Engine and Diesel Fuel. The train in question seems like it was a Diesel Engine, but predated what is now established as Diesel Fuel, or I guess #2 Diesel Fuel Oil, with Kerosene being #1 Diesel Fuel Oil, I think.
Yes, that picture was made by an artist, not an engineer. The top row makes sense once you add in the direct injection (which, by the way, is coming to gasoline cars near you; many Toyotas get them this fall.) The bottom row is jacked up, either per the discussion of the faux four cycle above or other reasons.
I love two stroke designs and consider them better engineering than four strokes. Sure, you pollute, burn some extra gas, etc, but the power to weight ratio of the engine is just insane compared to a 4 stroke. You get almost double the power per displacement, which makes a big difference for little engines like outboards and lawn equipment and motorcycles.
To Joe: Well nothing is added to the knowledge base by playing semantics games, I won't do it. I joined the discussion only to add something, not to prove or disprove who knows what. The railroads, the United States Navy, and the industry at large had different classifications for the the engines in discussion. If you want to call them all diesels because they are compression ignition engines be my guest. We also call fork lifts Towmotors. Even Wikipedia describes them as diesel engines and then continues to describe why they are really not. The idea of Rudolf Diesel being the god of CI engines has been totally completely thoroughly dis proven to everyone except perhaps Germans.
I am one bit smarter then you or perhaps only more experienced in a obvious respect: I know when to not assert myself in a discussion when I am well removed from my prime center of expertise and real world experience. I don't want to risk further dilution of the already rickety and failing human knowledge base. END!
I would bet that the distillate used by the locomotives was what we now call #6 oil.
It has to be heated to 180° in order to flow, but because it is so dense, it carries a lot of energy, and so is efficient to carry if you need extended range.
The 2cycle GM diesel is a true 2cyle with a power stroke every revolution. That training poster is very confusing.
Towards the bottom of the power stroke the piston uncovers the intake, the exhaust valves open (cam operated) and the super charger blowers in fresh air forcing out the exhaust and filling the cylinder with fresh air. As the piston moves up it closes the intake port and compresses the air. As the piston reaches tdc fuel is injected causing ignition and the start of the power stroke. All within 1 revolution.
Twice as many power strokes per rev ( at 2000rpm the sound like a 4 stroke at 4000rpm) and the noisy super charger gave rise to the nick name "Screaming Jimmy".
Last edited by Cutlass Fan; June 13th, 2016 at 08:35 PM.
June 1st, 2016, 09:43 AM
