Two-Stroke, Direct-Injection Engines
Direct-injection, two stroke technology is designed to significantly reduce HC emissions from engines used in outboard and personal watercraft applications. Unlike conventional two-stroke engine designs, this innovative technology precisely injects the fuel charge into the cylinder above the piston, after the exhaust port is closed. Since the exhaust port is closed at time of injection, unburned fuel cannot escape through the exhaust port. As a result, when compared to a conventional two-stroke engine, HC emissions are reduced by more than 80 percent and fuel efficiency is increased by 35-45 percent.
While manufacturers have evaluated many different direct-injection system designs, two are currently available in the marketplace and one is scheduled for introduction later this year. All three systems are capable of reducing HC emissions and increasing fuel economy. Direct-injection technology is currently available on outboards ranging in power from 90-to 225-horsepower and some 1999 model personal watercraft.
Outboard Marine Corporation (OMC) of Waukegan, Illinois, has developed a proprietary new low-emission engine technology based on a pressure-pulse system design. The FICHTTM fuel injection system is an electronically driven, high-pressure-pulse system that can blast an atomized charge of fuel directly into each engine cylinder at rates in excess of 7,000 times per minute at pressures exceeding 350 pounds per square inch. OMC offers this technology on outboard engines ranging from 90-to 225-horsepower. The company has also licensed the FICHTTM system technology to Polaris and Kawasaki for use on their personal watercraft and other products.
The Australian-based Orbital Engine Company also offers one of the industry's most widely accepted air-assisted, direct injection systems. Mercury Marine, based in Fond-du-Lac, Wisconsin, has introduced its OptiMaxTM engines, which are equipped with the Orbital-based technology. With the OptiMax system, high-pressure air is used to inject the fuel charge directly into the cylinder to achieve a stratified charge. Electronic control of the injection timing ensures the exhaust port is closed prior to the injection of fuel into the combustion chamber. Mercury Marine offers this technology on engines ranging from 135-to 225-horsepower.
Like the Orbital-based system, Yamaha Marine's direct-injection technology is also an air-assisted design that injects the atomized fuel charge directly into the cylinder at approximately 700 psi after the exhaust port is closed. This technology will debut on the company's new 2.6 liter V-6 engine, which will be available for the 2000 model year.
Several personal watercraft manufacturers are also developing air-assisted, direct-injection engines based on, or similar to, the Orbital technology. Orbital has also licensed its technology to several other marine engine manufacturers, including Bombardier Recreational Products for its Sea-Doo products, OMC and Tohatsu.
