The core of Pinnacle's technology resides in its "Cleeves Cycle," named after James Montague (Monty) Cleeves, founder of the company. The Cleeves cycle can switch back and forth from the Otto cycle (constant volume combustion) to the Diesel cycle (constant pressure combustion) depending on operating conditions. The result, according to Pinnacle, is an engine that's ultra-efficient and compatible with most fuels, including gasoline, diesel, natural gas, propane and biofuels.
Since it's just beginning to emerge from stealth mode, Pinnacle is still somewhat reluctant to divulge details on the Cleeves cycle and the engine's overall design. Pinnacle Engines has had one U.S. patent awarded (#7,921,817 (PDF warning), which happened April 12, 2011) and has filed additional patent applications.
Cleeves does claim that the company's mill nets "diesel-like efficiencies on this teeny gasoline engine." Furthermore, Cleeves said:
Tom Covington, Pinnacle's vice president of marketing and special projects, says that the Cleeves cycle engine doesn't require "whizz bang" technology and assures everyone that it "doesn't require magic." Whew.We're not interested in the real high power efficiency, because if you look at a drive cycle, you never run there. That 10 horsepower engine is running at 4 hp most of the time. Having a high peak efficiency at 10 hp doesn't help you if your efficiency at 4 hp isn't very good. We focus on making it efficient where people use it. Our peak numbers at those lighter loads are not the big 42 percent numbers, but that's where we get 30-50 percent difference between a conventional engine and us. We've moved our peak efficiency down where it's usable.
[Source: Green Car Congress]