Hofbauer, P., "Opposed Piston Opposed Cylinder (opoc) Engine for Military Ground Vehicles," SAE Technical Paper 2005-01-1548, 2005, doi:10.4271/2005-01-1548.
An extremely lightweight opposed piston opposed cylinder (opoc) diesel engine is under development by FEV Engine Technology under a Defense Advanced Research Projects Agency (DARPA) program. FEV and Advanced Propulsion Technologies (APT) were asked by the U.S. Army Tank Automotive Research Development and Engineering Center (TARDEC) to modify this engine for heavy-truck applications. Analyzing the two- stroke scavenging, the side-injection combustion, and the structure of the key components shows the potential of the opoc concept. It is predicted for the 465 kW (650 hp) opoc truck engine: Specific power of the dry engine ~2 kW/kg (1.2 hp/lb); Engine Height ~40 cm (16 in); Best Efficiency at two sweetpoints ~206 g/kWh (0.339 lb/hph).