Navistar’s International brand has been the number-one-selling medium-duty commercial truck for 20 years running. So when Navistar recently decided to sign a development agreement with EcoMotors to commercialize a radically new turbodiesel engine, we had to take a closer look.
Eric Tech, President of Navistar engine group, sounded confident in this potentially world-changing decision: Consistent with our leadership strategy, Navistar continues to seek innovative products, which differentiate us from the marketplace, while others embrace the status quo. Right now, Navistar and EcoMotors’ engineers are busy testing and developing a new version of the opposed-piston opposed-cylinder engine (OPOC), so we don’t have those specifications yet, but we can give you a taste of what’s to come by looking at the information released so far.
Professor Peter Hofbauer began working on opposed-piston opposed-cylinder (OPOC) engines that made more than 1 hp per pound in 2003. The first applications for his engines were unmanned helicopters, and then suitcase-sized portable generators for the United States military. Fast-forward eight years, and these power-dense OPOC engines are projected to appear in all kinds of vehicles.
More Pistons=More Power
Opposed-piston opposed-cylinder engines are scalable, have been created in several different displacements, and can be stacked together like Legos to build modular powerplants. Although there have been other opposed-piston opposed-cylinder engines before, this design has benefited from the financial backing of Bill Gates and Vinod Khosla. The Navistar-EcoMotors OPOC is an early front-runner in a growing segment, which is unlikely to go away with today’s volatile fuel prices and growing environmental concerns.
This opposed-piston opposed-cylinder two-stroke diesel engine has four pistons, two cylinders, and one crankshaft. The outer pistons (A) each have two connecting rods (B) that exert a pulling force on the crankshaft. The inner pistons (C) each have one connecting rod that pushes on the crankshaft (D). Since the pistons only travel half the distance of a normal engine, they can move much faster. There is one combustion chamber for two cylinders. The ports from left to right are: (1) intake, (2) exhaust, (3) intake, and (4) exhaust. This setup is reported to be naturally balanced, and all the forces are directed into the crankshaft instead of into the block. Therefore, it’s claimed that the block doesn’t need to provide as much structural strength as most engines require at the same power level. The prototype version shown here is made from lightweight magnesium.
The OPOC Advantage
The OPOC engine could represent the next generation in diesel technology, and its advancement may prove as potent to diesel performance as turbocharging, intercooling, and direct injection werecombined. EcoMotors promises its engine:
1. Uses 50 percent less parts and is projected to be much cheaper to make than today’s engines
2. Has no cylinder head or valvetrain to cause problems
3. Is capable of 15 to 50 percent better fuel economy
4. Does not create excess waste heat, so the need for a large cooling system is reduced
5. Creates fewer exhaust emissions, which negates the need for expensive exhaust aftertreatments
Inside Navistar’s Diesel Of The Future
Location: Allen Park, Michigan
Type: Two-stroke, opposed-piston opposed-cylinder (OPOC) turbodiesel
Cylinder bore: 3.937 inches (100 mm)
Dry weight: 296 pounds
Dimensions: 22.8L x 41.3W x 18.5H in.
Horsepower: 325 hp at 3,500 rpm
Torque: 664 lb-ft at 2,100 rpm
Power density: 1.1 hp per pound
4201 Winfield Road