Wärtsilä is a Finnish manufacturer of large diesel and gas engines for use in powering ships and electricity generation. The company's headquarters are located in Helsinki. The core business of Wärtsilä is marine diesel engines, but its engines are also widely used in diesel-powered power plants. It employed 18,810 workers as of 2008.
Wärtsilä engines are mainly used for marine propulsion and for electricity generation. The engines which Wärtsilä produces range from the 4L20, a four-stroke, medium-speed engine producing 720 kW (980 HP), to the Wärtsilä-Sulzer RT-flex96-C two-stroke diesel engine series which, in 2006, was reported as being one of the most powerful yet most compact prime-movers in the world. This model has a cylinder bore of 960 mm (37.8 in) and stroke of 2500 mm (98.4 in). The largest version produces up to 80,080 kW (107,400 HP) in the 14-cylinder configuration. These engines are used to propel large container ships, such as those of the A. P. Moller-Maersk Group. The vessels are known as the E-class ships; Emma Maersk was the first.
Wärtsilä produces a full line of four-stroke medium-speed engines, many of which are multi-fuel capable (diesel fuel, heavy fuel oil, vegetable oils, and natural gas) ranging up to the 20V46F which produces 23,000 kW (30,820 HP) operating at 600 RPM.
Wärtsilä also offers a full line of two-stroke, low-speed engines, ranging from approximately 3860 kW (5250 HP) up to 80,080 kW (107,400 HP). The two-stroke units are compact, and generate excellent power for their weight. However, on a per-horsepower basis, they also produce substantially more emissions than four-stroke units.