The typical tradeoff for a greener powertrain is higher cost. Electric vehicles, plug-in hybrids, Prius-type hybrids -- all come at a price premium.
But imagine an engine that promised a 30 percent increase in fuel economy and cost less. Automakers would race to get that kind of paradigm-buster into their cars, right?
Well, not exactly.
Three companies developing opposed-piston engines say they can produce the magic combination of sharply increased efficiency and lower costs. The trio -- EcoMotors International, Pinnacle Engines and Achates Power Inc. -- are refining a pre-World War II internal combustion scheme in which two pistons operate in a single cylinder.
But automakers remain wary, saying that use of opposed-piston engines on high-volume programs is years away.
For one thing, the EcoMotors and Achates engines are two-strokes, which characteristically have high hydrocarbon emissions and high oil use. The engine companies are trying to convince automakers that they can meet emissions standards. And they are starting to make inroads on the fringes of the industry.
Don Runkle, CEO of EcoMotors, points to a development deal with truckmaker Navistar International for a turbodiesel engine as establishing credibility.
"They obviously think our claims are real, and we are in the process of running test engines for them," he says. "This is not a theory."
But major automakers are a tougher sell. That's because big automakers plan powertrain programs in terms of billions of dollars of investments and a decade or more of lead time, says Dan Kapp, Ford's director of powertrain research and advanced engineering.
"When someone says, 'I've got a game-changing development,' you've got to understand what changing the game means to us in terms of time and investment," Kapp says.
But, he adds, Ford is not dismissing opposed-piston engines as an option.
"We do some deep internal technical vetting of these concepts," Kapp says. "We do take them very seriously."
The three competitors have their own takes on opposed-piston technology. But for all, improved fuel economy is central. Because of the engine design, that's linked to lower cost.
Opposed-piston advocates say that the engines can use many of the same parts, materials and tooling as today's internal combustion engines -- a piston's a piston, in other words. So there's no need to create a new supply chain.