Achates Power and Aramco Services recently announced they will put aon the road with a novel opposed piston engine under the hood, hoping to prove this exotic engine design is the future of burning gas powered vehicles.
Achates' opposed piston engine is a two-cycle, 2.7-liter, three-cylinder with six pistons arranged in a pair per cylinder, working against each other rather than each piston in its own cylinder working against a head and valves. Achates controls the engine's response curve by modulating pressures through both a supercharger and a turbo instead of varying valve lift and timing. No spark plugs, either -- the Achates design uses compression ignition like a diesel, but runs on gasoline.
The big idea is to end up with a more thermally efficient engine that gets more out of each drop of fuel. That's not a very high bar: Today's gas engines use around 25 percent of each gallon of gas to move the car, the rest going to wasted heat. Achates says it can push that to around 45 percent which, in the case of an F-150, could mean 37 mpg on a CAFE basis and perhaps 33 mpg observed. That's a big jump in a vehicle that uses a lot of fuel per mile, travels a lot of miles and sells in the highest numbers each year.
Achates isn't the only company developing a modern opposed piston engine for cars and light trucks. Pinnacle Engines has a version that uses a four-cycle process and spark ignition that it says will see its first test applications in the Chinese market. EcoMotors was another prominent competitor, but its intellectual property was put up for sale in late 2017.
Aramco Services, the US arm of the Saudi oil apparatus, will start testing the F-150 with an Achates opposed piston engine by late 2018. The auto industry will be interested to see what that proves about the engine's efficiency, reliability, emissions compliance and total cost to integrate into existing vehicle platforms.