Air Assisted Direct in-cylinder injection systems have now been in commercial production for over 18 months in large two-stroke outboard applications, offering the customer the advantage of emissions control, significant fuel economy improvements, smooth and misfire-free operation and improved driveability.
With the pending implementation of emission controls in most two-stroke engine applications, the fuel system of choice must be capable of being adapted in a short time period to a new or given application. Over the last three years, the air assisted direct injection system has been successfully applied across a range of cylinder displacements from 50 to 500cc. In all applications, the in-cylinder injection system's hardware has been maintained common in order to share in the benefits of economies of high volume production.
As the emissions targets are generally not as stringent as those called for in today's and future automotive engine requirements, the design requirements become product specific, defined by performance and the cost targets.
This paper provides an overview of what has been achieved on the production of the Mercury Marine Optimax low emission two-stroke outboard utilising Orbital technology on the 3.0L 200DFI model. The authors also discuss some of the design considerations across a variety of both demonstration and commercially released recreational and motorcycle applications.