SAN CARLOS, CALIF. --- Most internal combustion engines operate like trumpets, with punctuating valves controlling the flow of air, fuel and exhaust in and out of the cylinder.

Pinnacle Engines has come up with an engine that operates more like a trombone.

The company, founded in 2007, has developed a somewhat novel opposed piston engine that controls the flow of gases with a sliding cylinder sleeve -- typically an inert component that separates the cylinder from the rest of the engine -- instead of traditional intake valves.

The cumulative architectural changes allow Pinnacle’s engine to improve fuel economy by 25 percent to 50 percent, the company claims.

An Asian manufacturer has already agreed to adopt it -- assuming development continues as planned -- for two- and three-wheeled vehicles, said CEO Ron Hoge.

“We should be in production with our first engines in 2013,” he said.

The engine will cost more initially than other engines, but the premium can be made up in fuel economy, he added. With Pinnacle’s engine, three-wheelers, a common mode of transportation in India, can go 45 kilometers on a liter of gas instead of the usual 36 kilometers.

Put another way, a car with a six-piston Pinnacle engine can get the same mileage, but sport better performance, than a car with a standard four-piston engine.  

Although electric cars tend to grab most of the headlines, established companies and a select group of startups like Achates Power and EcoMotors are tinkering with ways to improve the efficiency of internal combustion engines. Electric car advocates like Nissan’s Carlos Ghosn and Elon Musk of Tesla Motors predict that electrics might constitute 10 percent to 13 percent of the car market by 2020. Thus, 87 percent of the market will need technology to meet the more stringent mileage standards in place in the EU, the U.S., China and other nations.

The big question is whether and how these startups will fare. Large auto companies historically have been reluctant to license outside technology, particularly from young companies. Only a few companies ever adopted the Wankel engine. Scuderi Engines has spent years on its engine but has yet to graduate beyond simulations.

Many others have extensive programs underway, as well. Ford, for instance, is concentrating most of its fuel economy efforts on its EcoBoost engine, a diesel-like gas engine that can boost fuel economy by 10 percent to 15 percent.

Gains in fuel economy can also be achieved through things like air conditioners powered by engine waste heat or microhybrid battery packs.

Hoge, though, points out that transportation will grow more rapidly in emerging economies like China and India and many of these new car companies don’t have decades of engine R&D or worldwide teams of engineering.

And, despite the fact that emerging nations often don’t have a great reputation when it comes to protecting intellectual property, Asia has become a destination for intellectual property startups. Most of the customers of Innovalight, which makes an ink to enhance solar panels, hail from China.

Pinnacle's engine, invented by Monte Cleeves, shares similarities with the engines from Achates Power and EcoMotors. All three are based around an opposed piston design. In most engines, a cylinder contains a single piston. In these engines, two pistons face each other from opposite ends of the same cylinder. The change effectively gives these engines a dynamic, more efficient compression chamber for burning fuel. Think about how it is easier to squeeze a rubber ball with your two hands instead of pressing it with one hand onto a flat, immobile table.

“Your combustion chamber is two working surfaces,” explained Achates CEO David Johnson earlier this year.

Combining two pistons into one cylinder also reduces the number of parts, leading to lower costs and, ideally, lower maintenance requirements. (Subaru and Porsche have boxer engines, which sport pistons positioned opposite from each other, but the pistons sit in their own cylinders.)

All three have a heritage that goes back to World War II. Junkers, the plane manufacturer of the Third Reich, developed opposed piston diesel engines for planes. The British used sliding sleeve engines in the Bristol and other planes.

The engines from Achates and EcoMotors, however, run on diesel. Pinnacle’s engine runs on regular gas, which is easier to find and doesn’t have the same baggage when it comes to particulate matter. It can also run on compressed natural gas or ethanol.

The Pinnacle engine is also a four-stroke engine (i.e., there are four separate segments to the compression cycle). The company calls it the “Cleeves Cycle.” Achates has a two-stroke cycle.

The sliding sleeve is also unique. With a sleeve, the port for letting in air and fuel or letting out exhaust can be as big as the entire circumference of the cylinder. It’s a void that is open and shut by sleeve. Traditional valves have smaller circumferences. Greater potential intake leads to performance gains.

Pinnacle’s biggest challenge in development has revolved around figuring out a way to keep the sleeve lubricated while simultaneously keeping oil out of the cylinder.

Right now, the company only has prototypes. (See video. That's Cleeves, by the way.) A pre-production version of the engine is due in around six months.

While Pinnacle will produce engines, it will also explore licensing and joint ventures. With the first customer, you won’t see the Pinnacle name on it. Instead, the engine will bear the name of the vehicle manufacturer, but it will be touted as the Cleeves Cycle engine.

NEA, Bessemer Ventures and Infield Capital put $13.5 million into the company in March.