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Development of Opposed-Piston Variable Compression Ratio Engine

Company Name: Pinnacle Engines
Program Office: Vehicles
Location: San Carlos, CA
Email:  James (Monty) Cleeves, Founder, President and CTO;
Award Amount: $200,203
Project Term: 12 months
Project Status: Active
Participating Lab(s): Oak Ridge National Laboratory


The demand for light-duty transportation vehicles, and the energy required to operate those vehicles, continues to increase and automakers are looking to adopt fuel-efficient technology to meet resulting policy requirements and consumer demand.

Pinnacle Engines has patented an opposed-piston, 4-stroke, reciprocating sleeve valve engine with variable compression ratio and variable valve timing.  The company has already demonstrated a 20 percent fuel economy increase over the world's best two-wheelers and it finds that the addition of exhaust gas recirculation alongside these other technologies expands the potential operating space immensely.

Working with staff at Oak Ridge National Laboratory, Pinnacle Engines will utilize computational fluid dynamics to study the engine's inner workings under various scenarios. These computational simulations will help identify complex design interactions, sensitivities, and determine optimum configurations to build into the design to maximize engine energy efficiency.  And the results will be verified in hardware within six months of completing this study. The use of high-powered software to study the engine will allow the company to leapfrog years of costly testing and allow it to deliver a new technology to the market with an industry-standard level of technical analysis.


The Pinnacle engine design combines the demonstrated high efficiency of the opposed piston diesel engine with four stroke spark ignited operation. The Pinnacle engine incorporates variable compression ratio and variable valve timing. The sleeve valve allows for engineered air delivery that enables fast combustion even with extreme dilution. The engine operates at greater than 15:1 effective expansion ratio with 50 percent dilution with exhaust gas recirculation so that operation at part loads is actually more efficient than state of the art turbocharged common rail diesel engines, without the added expense or emissions drawbacks.



Increasing internal combustion engine efficiency is a top priority for manufacturers. Improved engine designs can be easily integrated into existing factories and energy distribution networks. Helping consumers reduce gasoline expenditures allows them to increase spending on savings and other areas of the economy.


Maximizing fuel economy means minimizing gas burning and associated particulate generation, noxious gas emissions and heat-trapping emissions like carbon dioxide that cause climate change.


Improvements in average fuel efficiency of light duty vehicles will lower U.S. demand for foreign oil supplies. The Pinnacle engine is also capable of running on natural gas as an alternative to gasoline and other traditional automotive fuels.