You should check out the work of BRP (Bombardier Recreational Products) with the Evinrude ETEC Outboard engines. They are currently the most advanced DI 2-stroke engines available. These engines meet the most stringent emissions level (CARB 3-star). You can check out their website at
There are several SAE papers available, including:
2004-32-0011
Carbon Monoxide Emissions From Marine Outboard Engines
2004-32-0092
Life Assessment of Pm, Gaseous Emissions, and Oil Usage in Modern Marine Outboard Engines
2004-32-0039
Predicting and Optimizing Two-Stroke Engine Performance Using Multidimensional Cfd
2004-32-0013
The Effect of Fuel Spray Momentum on Performance and Emissions of Direct-Injected, Two-Stroke
Engines
2003-01-3103
Modelling of Air-Fuel Mixing in a Two-Stroke Direct Injection Engine
2003-32-0007
Optimization of the E-Tec Combustion System for Direct-Injected, Two-Stroke Engines Toward 3-Star Emissions
2004-01-2588 Development of Nasa High-Strength Aluminum Alloy for Use in the Evinrude Etec Outboard Engine
Regards,
MD