Two-stroke diesel engine

Nordberg two-stroke radial diesel engine formerly used in a pumping station at Lake Okeechobee

A two-stroke diesel engine is a diesel engine that works in two strokes. A diesel engine is an internal combustion engine that operates using the Diesel cycle. Invented in 1892 by German engineer Rudolf Diesel, it was based on the hot-bulb engine design and patented on February 23, 1893. During the period of 1900 to 1930, four-stroke diesel engines enjoyed a relative dominance in practical diesel applications. Charles F. Kettering and colleagues, working at the various incarnations of Electro-Motive and at the General Motors Research Corporation during the 1930s, advanced the art and science of two-stroke diesel technology to yield engines with much higher power-to-weight ratios than the two-stroke diesels of old.[1] This work was instrumental in bringing about the dieselisation of railroads in the 1940s and 1950s.[1]

All diesel engines use compression ignition, a process by which fuel is injected after the air is compressed in the combustion chamber, thereby causing the fuel to self-ignite. By contrast, gasoline engines utilize the Otto cycle, or, more recently, the Atkinson cycle, in which fuel and air are mixed before entering the combustion chamber and then ignited by a spark plug.

Two strokes

Model (cutaway) of a MAN B&W two-stroke marine diesel engine with the piston rod attached to a crosshead

Two-stroke internal combustion engines are simpler mechanically than four-stroke engines, but more complex in thermodynamic and aerodynamic processes, according to SAE definitions. In a two-stroke engine, the four "cycles" of internal combustion engine theory (intake, compression, ignition, exhaust) occur in one revolution, 360 mechanical degrees, whereas in a four-stroke engine these occur in two complete revolutions, 720 mechanical degrees. In a two-stroke engine, more than one function occurs at any given time during the engine's operation.

In most EMD and GM (i.e. Detroit Diesel) two-stroke engines, very few parameters are adjustable and all the remaining ones are fixed by the mechanical design of the engines. The scavenging ports are open from 45 degrees before BDC, to 45 degrees after BDC (this parameter is necessarily symmetrical about BDC in piston-ported engines). The remaining, adjustable, parameters have to do with exhaust valve and injection timing (these two parameters are not necessarily symmetrical about TDC or, for that matter, BDC), they are established to maximize combustion gas exhaust and to maximize charge air intake. A single camshaft operates the poppet-type exhaust valves and the Unit injector, using three lobes: two lobes for exhaust valves (either two valves on the smallest engines or four valves on the largest, and a third lobe for the unit injector).

Specific to EMD two-stroke engines (567, 645, and 710):

Specific to GM two-stroke (6-71) and related on-road/off-road/marine two-stroke engines:

Notable manufacturers

Brons two-stroke V8 Diesel engine driving a Heemaf generator


Works cited

Further reading


  1. Horsepower for naturally aspirated engines (including Roots-blown two-stroke engines) is usually derated 2.5% per 1,000 feet (300 m) above mean sea level, a tremendous penalty at the 10,000 feet (3,000 m) or greater elevations, which several Western U.S. and Canada railroads operate, and this can amount to a 25% power loss. Turbocharging effectively eliminates this derating


This article is issued from Wikipedia - version of the 11/4/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.