Basically, think of it like an inside-out horizontally opposed boxer engine. Each piston compresses a shared air and fuel mixture per cylinder, firing with the power of two pistons. Even though the pistons are joined to a separate crankshaft, maximum efficiency is possible thanks to a more complete ignition of each stroke.
An even more interesting thing about the design of this engine is the fact that it can run on variable fuels including petrol, ethanol and diesel. Yep, an engine that can run on diesel and petrol - we're not sure how a conventional exhaust with catalytic converters would operate though.
It can ignite both diesel and petrol thanks to its ability to switch from a conventional Otto four-stroke cycle, with ignition supplied from a spark plug, to a typical diesel-type compression cycle whereby the fuel mixture is ignited using only pressure and subsequent heat. Pinnacle Engines has also applied its own variable compression ratio feature which allows the engine to effectively alter its compression ratio according to conditions and fuels, on the go.
Pinnacle Engines says being able to switch from cycle to cycle has allowed the engine to be extremely efficient as well, up to 30-50 percent more efficient compared with conventional engines in fact. On top of that, since the engine is made up of much the same components as a conventional engine, costs to develop the layout are said to be relatively low.
Designer and founder of Pinnacle Engines, James Montague (Monty) Cleeves, recently said,
"This engine technology provides the fuel economy and CO2 emissions of a hybrid at a price that the whole world can afford."
There are plans for the engine to go into mainstream production, with a Pinnacle press release stating that it "is in the process of commercialising its technology through a joint development and licensing agreement with an Asian vehicle OEM". It's unknown which particular Asian manufacturer is developing the technology, but it's certainly an interesting concept and one to look out for in the future.