As automakers scramble to develop more efficient engines to meet increasingly tight fuel economy regulations, one company is claiming its new technology will change the auto industry.
“[Our] engine will be 50 percent more efficient,” explained David Johnson, the energetic president and CEO of Achates Power, a company founded in 2004 with the goal of revolutionizing internal combustion.
As numbers go, that’s a borderline preposterous figure, but making it even more unbelievable is that its engine is not being compared to some bunker-fuel-burning container transport ship, rather a state-of-the-art, turbocharged, downsized rival with gasoline direct injection like a Ford EcoBoost powerplant, for instance. The company also projects that a diesel-powered version will be 30 percent more efficient than the best oil-burners on the market today.
At a time when automakers are fighting tooth and nail for half-percent efficiency gains, a claim like Johnson’s seems as far off as the colonization of Jupiter’s moons, but he remains enthusiastic. “We have a very big contribution to make.”
Achates Power: Different by Design
What sort of black magic has Achates Power discovered that can allegedly cut fuel consumption by such an astonishing amount? What it has developed is an opposed-piston, two-cycle, compression-ignition engine. “It’s cleaner, more efficient [and lower cost]… than anything else on the market,” said Johnson, plus it has dramatically fewer components.
In simple terms, this engine has two pistons per cylinder that move toward and away from each other during a combustion cycle. Naturally, there are two connecting rods and crankshafts to support this arrangement, but despite these extra pieces, the elimination of cylinder heads and associated valvetrain still dramatically cuts the overall component count. Quantifying this, the company claims a 2.7-liter three-cylinder opposed-piston engine has 60 percent fewer parts than a similarly sized supercharged V6, a reduction that could also lower costs by 10 percent.
Curiously, this overall design is hardly new; the first instances of opposed-piston engines date back to the late 19th century, with numerous examples being produced over the past 100 years. In fact, these engines have successfully powered things like ships, tanks, and aircraft.
But to date, this technology has never really been used in road-going vehicles, certainly not in any significant volume, which is something Achates Power is looking to change. In essence, it has taken a fundamentally tried-and-true idea and attacked it with copious amounts of modern engineering.
Aside from being simpler, cleaner and cheaper, this opposed-piston design is even energy agnostic. With appropriate calibration, it can run on gasoline, ethanol, natural gas, diesel, or even other fuels. For all these reasons and more, Johnson said, “This actually is the ultimate engine.”
Unlike conventional four-cycle internal-combustion powerplants, Achates Power’s unique design requires forced induction; it could never operate naturally aspirated. According to Johnson, this is because “the pistons don’t do any work breathing in our engine.” In other words, they never create vacuum during an intake stroke or force exhaust gasses out the tailpipe like conventional engines.
For each combustion cycle, fresh air is forced into the cylinders by the blowers. This incoming stream also helps push the exhaust out. As the pistons move together the air gets compressed, then a precise amount of fuel is squirted into each chamber where it auto ignites, burning quickly and cleanly.
Superior thermal efficiency helps this opposed-piston design deliver up to 50 percent better efficiency. Heat loss to the cooling system is lower, the expansion ratio is higher, there are reduced pumping losses and it can even run a leaner air-fuel mixture.
Further improving efficiency, with less work to do a vehicle’s cooling system can be made lighter. Cleaner combustion also allows exhaust after-treatment systems to be downsized, reducing mass, complexity and cost.
Another benefit is this engine’s much flatter fuel map, which means it doesn’t need a transmission with some crazy number of speeds to deliver optimum fuel economy. Simply put, it operates more efficiently more of the time than a traditional four-cycle engine.
Road Ready… Almost
Proving its lofty claims, the company is putting together a drivable test vehicle. By the end of 2018, it will have completed work on a light-duty truck as well as a 2.7-liter three-cylinder opposed-piston diesel engine. This unit is expected to offer around 270 horsepower with 480 lb-ft of torque.
As for fuel consumption, Johnson said it will beat fully phased-in CAFE 2025 requirements. The rig it is building is estimated to deliver 25 miles per gallon in urban driving and 32 on the highway. Combined, it should average 28 mpg, figures that are better than what’s offered by some midsize sedans. However, this engine’s CAFE score could be as high as 37. Johnson said this engine design is the most cost-effective way to meet upcoming fuel-economy regulations.
Of course, this engine works perfectly well with other efficiency-boosting technologies. If an automaker wants to go with lightweight materials, offer hybridization or run on biofuel, there’s no problem whatsoever.
Naturally, what Achates Power is developing has not escaped the notice of automakers. Right now, the company is working with nine different OEMs plus a handful of engine manufacturers to bring this exciting technology to market. It has also partnered with organizations including the U.S. Army and Argonne National Laboratory.
Not surprisingly, Achates Power’s hard efforts over the last dozen or so years is protected by a passel of patents. So far, it has been awarded 135, but an additional 230 are in the works.
Thanks to its combination of mechanical simplicity, combustion efficiency and power density it looks like the opposed-piston engine has a bright future. Johnson said in the early days of this project he used to question whether any manufacturer would ever introduce one of these engines, but “that day has long since passed.” He said an Achates Power-designed engine will reach the market, it’s just a question of when.
Check out our Feature Stories Section