23 February 2011
Navistar International Corporation has reached a development agreement with EcoMotors International™ in support of the company’s opoc® (opposed-piston, opposed-cylinder) engine architecture. EcoMotors’ first product targeted for commercial application is a turbo-diesel version of the opposed-piston, opposed-cylinder engine.
EcoMotors’ internal combustion engine design concept can operate on a number of different fuels, including gasoline, diesel, natural gas and ethanol. The opoc’s opposed piston-opposed cylinder direct gas exchange operation has been designed to provide the emission benefits of 4-cycle engines, combined with the simplicity of 2-cycle engines and the high power density typical for the opposed piston engine.
The opoc engine comprises two opposing cylinders per module, with a crankshaft between them—each cylinder has two pistons moving in opposite directions. This design configuration eliminates the cylinder-head and valve-train components of conventional engines, offering a compact core engine structure. The opoc engine operates on the two-stroke principle, with a high scavenging ratio, which is said to produce engine emission performance similar to a four-cycle engine. The power density of the opoc engine is very high, approaching one hp per pound.
EcoMotors’ intellectual property also includes an electrically controlled turbocharger technology which incorporates an electric motor in the turbo assembly to control boost pressure resulting in several advantages, such as improved combustion efficiency, electrically controlled variable compression ratio, improved fuel economy, and improved low-end torque.
The opoc engine is well balanced, enabling stackable power modules. To take advantage of the engine’s modular displacement capability, the design includes an electrically controlled clutch assembly that is housed between two engine modules and engaged when vehicle power demands require both modules to deliver power. When the power of the second module is not needed, the clutch is disengaged, allowing the second engine to stop completely.
The opoc engine has 50% fewer parts than a conventional engine, which is expected to allow for low cost, efficient manufacturing and increased durability. Navistar anticiaptes that working models of the engine will be ready for in vehicle testing within two to three years.