Eric P. Dion

The Achates Power Opposed-Piston Two-Stroke Engine: Performance and Emissions Results in a Medium-Duty Application

Historically, the opposed-piston two-stroke diesel engine set combined records for fuel efficiency and power density that have yet to be met by any other engine type. In the latter half of the twentieth century, the advent of modern emissions regulations stopped the wide-spread development of twostroke engine for on-highway use. At Achates Power, modern analytical tools, materials, and engineering methods have been applied to the development process of an opposedpiston two-stroke engine, resulting in an engine design that has demonstrated a 15.5% fuel consumption improvement compared to a state-of-the-art 2010 medium-duty diesel engine at similar engine-out emissions levels. Furthermore, oil consumption has been measured to be less than 0.1% of fuel over the majority of the operating range. Additional benefits of the opposed-piston two-stroke diesel engine over a conventional four-stroke design are a reduced parts count and lower cost.

Modernizing the Opposed Piston, Two Stroke Engine for Clean, Efficient Transportation

Opposedpiston (OP) engines were once widely used i n ground and aviation applications and continue to be used today on ships. Offering both fuel efficiency and cost benefits over conventional, fourstroke engines, the OP arch itecture also features size and weight advantages. Despite these advantages, however, historical OP engines have struggled with emissions and oil consumption. Using modern technology, science and engineering, Achates Power has overcome these challenges. The result: an opposedpiston, twostroke diesel engine design that provides a ste pfunction improvement in brake thermal efficiency compared to conventional engines while meeting the most stringent, mandated emissions requirements.