If you have ever used a chainsaw or a weed-wacker with a two stroke engine, you have experienced the two-stroke advantage. A two stroke engine can produce roughly twice the power of a same-size four-stroke engine because you get twice as many power strokes when the engine is running at a given RPM.
The same thing happens when a diesel engine is designed to run in a two-stroke mode. You get more power from the engine when compared to the normal four-stroke mode. The diesel two-stroke configuration is so efficient and powerful that it is often used in train locomotives. This article describes the basic operation of a two-stroke diesel engine:
A quick summary: A two-stroke diesel engine requires a blower to compress intake air. When the piston hits the bottom of the stroke, it opens a set of intake holes in the cylinder wall. The exhaust valve also opens that the top of the cylinder. The exhaust gases flow out the exhaust valve and fresh air pours into the cylinder (under pressure) through the intake holes. The piston compresses this air as it rises and diesel fuel is injected at the top of the stroke.
The following video is cool because it lets you look inside an actual 2-stroke diesel engine and see exactly what is going on. If you have ever been curious about how a 2-stroke diesel engine works, this is a great video: