"Power density is the Holy Grail of engine design." That is the mantra of Professor Peter Hofbauer, the chairman and chief technical officer of EcoMotors International.
Power density increases when there is more power with less weight. Professor Hofbauer's new opposed-piston opposed-cylinder (opoc) two-stroke engine has unprecedented power density: according to a company spokesman, this breakthrough engine design is 50 percent lighter, is half the size, and is at least 15 percent more efficient in the diesel version now under development. (It can use gasoline, ethanol, diesel – any liquid fuel.) However, EcoMotor's most powerful model to date achieves fuel economy that is 45 percent better than the current, state-of-the-art conventional turbo diesel engines.
Because the opoc(TM) has fewer components (13 versus 40 in an inline-4), it is less expensive to manufacture. Because it is a redesigned standard engine needing no new infrastructure, it can revitalize American manufacturing. Indeed, an EcoMotors handout proclaims, "that means real jobs, real soon."
The opoc(TM) has been in development for eight years, supported by public and private research funding. Professor Hofbauer, a 20-year veteran of Volkswagen, is the founder of EcoMotors, a three-year-old company in suburban Detroit. He explains that the opoc(TM) engine is a hybrid of the boxer engine – the type of flat engine in VW Beetles – and the famous Junkers (pronounced "yoonkers") diesel aircraft engines.
The boxer engine features a central crankshaft and the flat, opposed-cylinder design, but it has cylinder heads and valve train components. The Junkers engine features opposed pistons, but it has parallel crankshafts geared in tandem. In designing the opoc(TM) engine, Professor Hofbauer combined the benefits of the central crankshaft and the opposed cylinder design of the boxer engine with the advantages gained by having opposed pistons sharing a single injection of fuel mixture and eliminating cylinder heads and valve train components. Having two pairs of cylinders as they are laid out in the opoc(TM) engine represents a more balanced design and results in smoother operation.
If one engine with four cylinders is good, wouldn't adding another four be great? Indeed, the EcoMotors engine is designed to be a modular unit that can be teamed with additional units. At present, there are two engine models under development, the EM65 and the larger displacement EM100, and they are each regarded as a power module. Each of them can be paired up with a second unit to double the horsepower. If a vehicle equipped with a dual-module version of the EM100 (for example) is being operated at low speed or on flat terrain, it may not need the additional 325 hp that would be gained from the second module. When more power would be needed, though, that second module would be engaged with an electrically controlled clutch that would essentially shift the engine into a more powerful operating mode much like an automatic transmission. This mechanism would eventually reverse to decouple the second module to return it to more economical operation. EcoMotors terms this "modular cylinder displacement," an obvious enhancement to fuel economy that was promulgated by the EPA more than a decade ago. The spokesman for the company notes that Mercedes, for example, offers a comparable fuel-savings feature by taking half of its engine cylinders offline, but these unfueled cylinders still move and impact operation, if only slightly. With the EcoMotors' clutch, the module is completely detached and has no impact on the drive train. As mentioned previously, the modular cylinder displacement feature for a dual-module configuation of the EM100 makes fuel efficiencies of up to 45 percent attainable.
Another feature that enhances the EcoMotors engine is its electro-mechanical turbo-charger with no lag time in its power boost. This provides the advantage of instantaneous torque that is an appealing feature of electric motors.
Professor Hofbauer owns some of the more than 100 patents that protect the opoc(TM) engine design and the company owns some of them. The patents are for the engine designs and encompass designs using any fuel – gasoline, diesel, or ethanol. At present, EcoMotors is working with Eurocopter, as power density is extremely important in aviation.
It's natural to think of automotive applications when it comes to internal combustion engines, but in fact, the EcoMotors engine design is deliberately versatile, or, as they like to say, "application-agnostic." For those who like specs, the EM100 dual-module engine weighs 296 pounds, is just under 23x42x19 inches, has 325 hp at 3,500 rpm, and a power density of 1.1 hp per lb.
EcoMotors International has some impressive funding partners in Khosla Ventures and Bill Gates, and expects to have engine models ready for production by 2013. While the company has partnered with Eurocopter on one diesel engine project, it is presently consulting and communicating with other manufacturers about prospective partnering projects. Esquire Magazine, which featured the opoc(TM) two-stroke engine as its "Innovation of the Year" in last October's car-of-the-year spread, speculates that the powerful little 40-pound prototype motor – it can power a house – that CEO Don Runkle hauls out of a case when he goes to a meeting may be enough to convince many industry decision-makers "that the Engine That Changes Everything may have finally arrived."
We know Professor Hofbauer believes the challenge of greater power density is specifically his Holy Grail in engine design. For auto executives catering to the American market, that translates to an engine that could power the popular SUVs and light trucks that still accounted for more than half of passenger vehicle sales in 2007. Moreover, in today's economy, jobs in the U.S. auto industry might also be considered the Holy Grail of engine design.
Any way you look at it, though, before you know it, the Holy Grail of engine design may be coming to a showroom near you.
