Pinnacle, FEV developing opposed-piston engine for emerging markets
April 19, 2012, Automotive Engineering International Online – Pinnacle Engines has developed an ultra-efficient engine design based on a four-stroke, spark-ignited (SI), opposed-piston, sleeve-valve architecture using conventional engine manufacturing technology. The company says that the architecture, developed in-house in conjunction with FEV, incorporates two old efficiency ideas into one package, improving both in the process.
Opposed-piston engines have been around for quite some time in two-stroke form but suffer from an emissions perspective.  Sleeve-valve engines had some decided advantages in knock resistance and power density, but they too had emissions-related challenges due to the sleeves’ lubrication circuit.