I had the opportunity to speak at the Engine Expo in Stuttgart this week. I was struck, as I always am, by the number of unconventional engines being promoted by small companies. There were new engine concepts from the U .S., Germany, England and the Democratic Republic of Georgia.
While I admire the inventiveness and ambition of the entrepreneurs behind these new companies, I don’t envy their task. The great age of engine innovation, it seems to me, was in the early part of the last century, when talented and hard-working engineers used their mechanical intuition to try a wide variety of engine ideas. By the second half of the last century, engine designs coalesced around the basic four-stroke concept of today. While implementations vary widely—from small, one-cylinder gasoline engines to very large natural gas or diesel engines—the basic architecture of engines serving a wide range of applications is similar.
After a century of refinement, today’s engines are very good, with incredible advances in reducing emissions while improving efficiency and durability. Although mechanical intuition is necessary for innovation, it’s no longer sufficient. New engine concepts have to be thoroughly modeled and analyzed to have any chance of being adopted and working prototypes, carefully assessed, are required. The tools, talent and time needed to model, analyze, design, fabricate, test and refine new engine concepts require a substantial financial investment. And, it’s very difficult to assemble the financial and technical resources for the task.
At Achates Power, we’ve been fortunate to gain the financial and technical backing to develop the opposed-piston, two-stroke engine. When assessing new engine concepts, I advise you to consider three important topics:

  • Whether there is a scientific basis for the performance claims.
    We published the paper, Thermodynamic Benefits of Opposed-Piston Two-Stroke Engines, in order to lay out the basis for the thermodynamic advantage of opposed-piston, two-stroke engines.
  • Whether there is measured data to support the performance claims—including both emissions compliance and fuel economy improvements—across the full operating range of the engine.
    We’ve accumulated more than 4,000 hours of dynamometer testing to establish and refine the performance and emissions capability of our engine design, as well as to conduct an initial durability test. We’ve published the development process and performance results numerous times. We measure and publish results based on the Supplement Emission Test used in both the U.S. and Europe to calculate cycle-average results. Our engine has demonstrated a 21% fuel efficiency gain when compared to leading, conventional diesel engines while meeting the most stringent, global emissions requirements.
  • Whether the practical challenges of any new engine concept have been addressed, including cost, packaging and durability.
    We’ve rigorously addressed these issues internally, and have published the results of some of our evaluations.

The last new engine architecture to have a material impact on the industry was the Wankel engine from half a century ago, and for good reason—the conventional, four-stroke engine design is very capable. Only by assembling significant financial and technical resources, and expending them over a period of years in rigorously designing and validating our opposed-piston engine enhancements, have we been able to markedly improve upon the standard.

Clean Diesel Engine Engine Design