2-Stroke Fuel Consumption Reduced by 40% in Initial Testing

A team of engineers from Cobra AERO, Hillsdale Michigan [www.cobra-aero.com] and Jetfire Power, LLC, Brighton Michigan [www.jetfirepower.com] have conducted initial tests that show a dramatic reduction in fuel consumption in a small (33cc/cyl.) three-cylinder two-stroke cycle engine. The base engine [A99HF] was provided by Cobra AERO. The Jetfire Power Team designed a new head which included the patented Jetfire Combustion System. “Our goal is to reach compression ignition levels of efficiency but doing so with a lightweight and compact two-stroke engine platform,” commented Sean Hilbert, President of Cobra AERO.

The experiments were conducted at part load at 3000 rpm and 5000 rpm, which are conditions of commercial interest for various applications (video on next page). In dynamometer testing, the greatest improvement was at the 5000 rpm condition, showing a 41.6% fuel economy improvement versus the base engine. At 3000 rpm an estimated 41.1% fuel economy improvement was observed. These results do not include the potential ancillary reductions which, based on previous experience, are expected to be minimal. “We have been refining the Jetfire pre-chamber combustion system for over a decade,” said Harold Schock, Founder of Jetfire Power, LLC., “And its application on a two-stroke platform unlocks even more efficiency mechanisms compared to other combustion engine technologies. With envisioned calibration improvements, our team believes a 50% fuel economy improvement over a traditional two-stroke configuration is within reach.” An A99J-2S equipped with a generator has the potential to provide nearly 10kWe output which can be held in one hand.

These were the first known experiments where a controlled stoichiometry combustion prechamber has been employed on a two-stroke engine. Applications for this system include long-distance/high load lift drones, small portable generators, or emergency chargers for electric vehicles. Specific use cases for the A99J-2S include powering Group 2 UAS and providing forward operating electrical power. Larger versions of the engine could have many other applications. The work was conducted at the Energy and Automotive Research Laboratory at Michigan State University.