| Cutaway diagram of the opoc engine. Click to enlarge. |
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 International’s first product targeted for commercial application is a turbo-diesel version of the opposed-piston, opposed-cylinder 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 an efficient, compact and simple core engine structure. With a two-module application configured at the appropriate power level (to deliver a combined 480 hp), the opoc unit could deliver about 45% better fuel efficiency compared to a conventional heavy-duty diesel engine in a Class 8 truck, the company has suggested, while delivering emissions at the US Tier 2 Bin 5 level (the 50-state level in the US for diesel light duty vehicles). (Earlier post.)
We continue to be on the cutting edge of technology and our development agreement with EcoMotors once again demonstrates our commitment to develop new, innovative approaches to the commercial vehicle industry. Our company has a long history of pushing the envelope to deliver state-of-the-art, customer-focused solutions and we see great promise in EcoMotors’ breakthrough engine design.
—Dan Ustian, Navistar chairman, president and chief executive officer
EcoMotors’ patented engine design creates a family architecture that will operate on a number of different fuels, including gasoline, diesel, natural gas and ethanol. The opoc’s new opposed piston-opposed cylinder direct gas exchange operation provides the emissions benefits of 4-cycle engines, the simplicity benefits of 2-cycle engines, the power density of the less well known opposed piston engine, and the developments in electronics and combustion technology all tied together in a new and proprietary engine architecture.
Greater power engine density delivers an important benefits will result, including: lower weight; smaller size; lower material costs; lower friction; greater fuel efficiency; lower emissions; and lower heat rejection. The opoc engine has very high power density of nearly one horsepower per pound.
The engine is perfectly balanced, enabling stackable power modules. This modular displacement capability can yield high efficiency, plus much less NVH than a conventional engine of comparable power. With 50% fewer parts than a conventional engine (including no cylinder heads or valvetrain), the design also allows for low-cost, efficient manufacturing and increased operating durability.
EcoMotors’ intellectual property also includes an electrically controlled turbocharger technology which incorporates an electric motor in the turbo assembly to regulate boost pressure resulting in:
- Improved combustion efficiency to meet emissions;
- Electrically controlled variable compression ratio;
- Improved vehicle fuel economy;
- Enhanced vehicle drivability due to improved low-end torque;
- Eliminates Turbo lag; and
- Waste heat recovery by generating electricity.
Electrically Controlled Clutch. The development in clutch technology enables customers to take advantage of the engine’s modular displacement capability. The clutch assembly is housed between two engine modules, and is 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. This not only improves fuel economy by reducing parasitic losses, but also improves the efficiency of the primary module.