"True diesel"

[Lithonia Operator]

My sailboat's diesel engine has glowplugs to use on cold days. On warm days it will start without use of the glowplugs.

Is it a true diesel?

[timz]

50+ years ago, I was told that locomotive and truck diesels aren't true diesels -- it's ships that have true diesels. Don't recall the difference -- maybe the huge slow-turning diesels come closer to maintaining constant pressure during the piston stroke, and that's the criterion?

[Lithonia Operator]

Thanks, Beau. Got it.

[BEAUSABRE]

Back in the day there were semi-diesels as opposed to true diesels. 

"The semi-diesel or hot-head engine is not a true diesel, but retains the operating functions of the diesel with the exception of high compression. On these engines, the head or a bulb in the combustion chamber is heated to near red heat, usually with a kerosene torch. The engine usually has a manual pump that will force an amount of fuel that will be sprayed through a nozzle in the combustion chamber against the heated area. As the engine is rolled against compression, the manual pump is activated and the sprayed fuel ignites. This in turn creates pressure in the combustion chamber against the piston, thus starting the engine."

Remember the model airplane you flew as a kid? The one where you attached leads from a battery to heat the cylinder before you released the spring loaded prop? That's what's known as a glow plug engine, the semi-diesel is a giant version of that. Notice how the heating leads are removed at the beginning of this video

1962 Herkimer OK Cub .024 c.i. model glow plug engine - Bing video

What makes it a "semi-diesel" is that there is no sparkplug, like an Otto type engine, but engine compression is not high enough to heat the air in the cylinder to a temperature where the fuel ignites when injected, like a Diesel.

Here is a video of a semi-diesel in operation - note the use of the torches to heat the cylinders before it is cranked up

Gardner 4T5 Semi Diesel - Anson Engine Museum - - Bing video

[Backshop]

Lithonia Operator

Reading an article on early diesel locomotives, I came across the term "true diesel." 

As opposed to what?

 

What diesels specifically?  Some of the early small locomotives were diesel-mechanical, like a car.  So maybe they meant it as opposed to diesel-electric.

[Lithonia Operator]

Reading an article on early diesel locomotives, I came across the term "true diesel." 

As opposed to what?