Achates Power 2.7L OP engine. Click to enlarge.

Gasoline Compression Ignition (GCI) uses a gasoline-type fuel, but rather than ignited with a spark, it is compression-ignited like diesel. GCI engines operate at higher compression ratios than conventional gasiline engines, thus improving overall thermal efficiency. GCI could therefore be a best-of-both-worlds engine technology: combining the fuel efficiency of diesel engines with the low NO_x and soot-particle emissions of gasoline.

At NAIAS 2017, Achates Power announced it was developing a 2.7-liter, 3-cylinder (i.e., six-piston) light-duty version of its opposed piston engine (OPE) in both diesel- and gasoline-fueled versions. At that time, Achates said it would demonstrate the engine in 2018 in a driveable light-duty truck.

The developments stems from a major project partially funded with a $9-million grant from the Advanced Research Projects Agency - Energy (ARPA-E) to develop an opposed-piston two-stroke gasoline compression ignition engine (OPGCI) (earlier post).

The 2.7-liter compression-ignition OPE will will be 30-50% more fuel efficient than comparable diesel and gasoline direct injection engines, reduce emissions and cost less than alternative technologies under development for meeting 2025 CAFE fuel economy and Tier 3 emission targets.

For its part, Aramco, in collaboration with KAUST, has been investigating low-octane fuels for use in GCI engines. (Earlier post.) In a paper published in April 2017, Gautam Kalghatgi from Saudi Aramco and Bengt Johansson from KAUST observed that gasoline compression ignition engines can be run on gasoline-like fuels with a long ignition delay to make low-nitrogen-oxide low-soot combustion very much easier.

Additionally, the research octane number of the optimum fuel for gasoline compression ignition engines is likely to be around 70—hence surplus low-octane components in refineries could be used without much further processing, they suggested.

We have significant experience within the global fuel technology team related to fuels and engines, and we’re impressed by the work that Achates Power has done to bring their efficient, low-emissions Opposed-Piston Engine forward. The Achates Power OP Engine has the potential to revolutionize the internal combustion engine. Our joint collaboration with Achates Power is part of our larger R&D program to develop a full range of sustainable transport technologies.

—Dr. David Cleary, director of the Aramco Research Center in Detroit

Cleary joined Aramco after almost 20 years with GM R&D.

Aramco has incredible research and development capabilities, focused on improving the emissions and efficiency of the internal combustion engine, and we’re happy to be working with them on the continued development of the OP Engine. The 2.7L engine OPGCI engine we’re showing at NAIAS is a great first example of the combination of expertise from both Achates Power and Aramco and we’re looking forward to what the future holds.

—David Johnson, president and CEO, Achates Power

Resources

• Javed, T., Ahmed, A., Lovisotto, L., Issayev, G., Badra, J. Sarathy, M.S., & Farooq, A. (2017) “Ignition studies of two low-octane gasolines.” 185, 152–159 doi: 10.1016/j.combustflame.2017.07.006

• Gautam Kalghatgi, Bengt Johansson (2017) “Gasoline compression ignition approach to efficient, clean and affordable future engines” Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering doi: 10.1177/0954407017694275