Gasoline Direct Injection - in Two-stroke Engines

In Two-stroke Engines

The benefits of direct injection are even more pronounced in two-stroke engines, because it eliminates much of the pollution they cause. In all two-strokes, the exhaust and intake ports are both open at the same time, at the bottom of the piston stroke, for "scavenging". In conventional two-strokes, a portion of the fuel/air mixture entering the cylinder from the crankcase through the intake ports goes directly out, unburned, through the exhaust port. With direct injection, only air (and usually some oil) comes from the crankcase, and fuel is not injected until the piston rises and all ports are closed.

Some Goliath and Gutbrod two-stroke cars built in the early 1950s had mechanical direct injection, but their engines were soon superseded by four-strokes. The two-stroke vehicles showed very good performance and up to 30% less fuel consumption over the carburetor version, primarily at low rev. The cars had problems to start, however, when the engine was warm due to the vapor lock. Moreover, very few people knew direct injection at that time. That's the reason why branded repair shops and Bosch services had been sometimes so overloaded, that many cars were gladly converted to carburetor.

Two types of GDi are used in two-strokes: low-pressure air-assisted, and high-pressure. The former, developed by Orbital Engine Corporation of Australia (now Orbital Corporation) injects a mixture of fuel and compressed air into the combustion chamber. When the air expands it atomizes the fuel. The Orbital system is used in motor scooters manufactured by Aprilia, Piaggio, Peugeot and Kymco, in outboard motors manufactured by Mercury and Tohatsu, and in personal watercraft manufactured by Bombardier Recreational Products (BRP).

The high-pressure direct injector for two-stroke engines was developed in the early 1990s by Ficht GmbH of Kirchseeon Germany. Outboard Marine Corporation (OMC) licensed the technology in 1995 and introduced it on a production outboard engine in 1996. OMC purchased a controlling interest in Ficht in 1998. Beset by extensive warranty claims for its Ficht outboards and prior and concurrent management-financial problems, OMC declared bankruptcy in December 2000 and the engine manufacturing portion and brands (Evinrude Outboard Motors and Johnson Outboards), including the Ficht technology, were purchased by BRP in 2001.

Evinrude introduced the E-Tec system, an improvement to the Ficht fuel injection, in 2003, based on U.S. patent 6,398,511. In 2004, Evinrude received the EPA Clean Air Excellence Award for their outboards utilizing the E-Tec system. The E-Tec system has recently also been adapted for use in performance two-stroke snowmobiles.

Yamaha also has a high-pressure direct injection (HPDI) system for two-stroke outboards. It differs from the Ficht/E-Tec and Orbital direct injection systems because it uses a separate, belt driven, high-pressure, mechanical fuel pump to generate the pressure necessary for injection in a closed chamber. This is similar to most current 4-stroke automotive designs.

EnviroFit, a non-profit corporation sponsored by Colorado State University, has developed direct injection retrofit kits for two-stroke motorcycles in a project to reduce air pollution in Southeast Asia, using technology developed by Orbital Corporation of Australia. The World Health Organization says air pollution in Southeast Asia and the Pacific causes 537,000 premature deaths each year. The 100-million two-stroke taxis and motorcycles in that part of the world are a major cause.