I’m french and in France diesel locomotives have 4 times diesel engines. I d’ont know how working a 2 times diesel enginein north america [:(]
I presume you are referring to the difference between four-stroke-cycle and two-stroke-cycle engines.
A four stroke engine has a design similar to that used in most passenger road vehicles, relying on valves in the cylinder head to admit clean air and vent the exhaust gases. Each event (intake, compression, power, exhaust) takes a full stroke of the piston, or 180 degrees of crankshaft rotation. Each cylinder delivers power once in 720 degrees of crankshaft rotation.
A two stroke engine has a very different design. Exhaust is vented and clean air is admitted through ports which are exposed when the piston approaches the bottom of its stroke and closed as the piston moves upward. The cycle has the same four events, but intake and exhaust happen at the same time. As a result, each cylinder delivers power once in every 360 degrees of crankshaft rotation. Two stroke engines require some system to pressurize incoming air, since they only have about 45 to 60 degrees of crankshaft rotation to clear exhaust gases and replace them with fresh air.
Due to a shorter power stroke and some exhaust fouling of the compressed air, a two stroke engine delivers perhaps 160 percent of the horsepower of a four stroke engine of equal displacement running at the same RPM.
There have been two stroke engines with opposed pistons in open-ended cylinders (Fairbanks-Morse in the US, and the Napier Deltics in the UK,) which had much better exhaust-clearing characteristics at the expense of using multiple crankshafts. The two stroke engines manufactured by EMD and GE in the United States are of conventional design, with one crankshaft and closed-top cylinders.
Hope this helps
Chuck
General Electric FDL engines are 4-stroke.