San Diego’s Achates Power, a startup developing a radical new design for a diesel-powered truck engine, is blowing its own air horn today about its progress in demonstrating significant improvements in the efficiency and performance of its engine.
Through a series of tests that began just over a year ago, Achates says its prototype has shown improved fuel efficiency, while also meeting the new EPA10 emission standards for heavy trucks, which seek a seven to 20 percent reduction in greenhouse gas emissions by 2018. Achates says its independently verified tests show a 20-percent reduction in diesel fuel consumption when compared to the Power Stroke diesel engine that Ford introduced in April for its Super Duty truck line. (By coincidence, Xconomy San Francisco editor Wade Roush has a story today about efforts by ATDynamics of South San Francisco to help the trucking industry shave fuel costs by reducing drag.)
Achates has designed its two-stroke, “opposed-piston” internal combustion engine to be smaller, lighter, and more efficient that a conventional heavy-duty diesel engine with separate, in-line cylinders.
“If you’re in the industry, everybody knows that opposed-piston engines have the potential to be more efficient,” says Achates CEO David Johnson. “But the vast majority of engineers say, ‘Yeah, yeah, that’s all true, but you still have to meet these tougher emission standards.’ We did that more than a year ago, in September 2010, and we’ve consistently improved since then.”
Johnson previewed Achates’ engine design in a presentation at UC San Diego last year at the Xconomy Forum on the Rise of Smart Energy. Instead of cylinders that operate independently under a cylinder head, the opposed-piston design puts two pistons inside the same cylinder. Internal combustion occurs in the space between the two pistons as they come together, driving each cylinder outward, in the opposite direction, in what’s known as a two-stroke cycle.
Because Achates’ design has no cylinder head, the engine is lighter. And the dual-piston design means compression ratios are higher, so devices used to measure torque, or power, show the design gets more power for the same amount of fuel.
In a comparison with Ford’s Power Stroke engine, Johnson says its tests show similar emission levels out of the engine and reduced weight, cost, and complexity of the engine itself. Achates says its test also showed less than 0.1percent fuel-specific oil consumption, a measure of fuel efficiency within a crankshaft-design reciprocating engine.
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