Although two-stroke engines have mostly been abandoned due to relative inefficiency, high noise and harmful emissions, and the automotive industry is focusing its development efforts on efficient four-stroke engines and electrification, it seems that General Motors still sees the potential for the return of two-stroke units. The American manufacturer submitted an application to the Patent Office there, which describes a new system intended to modernize that technology.
The patent, filed last year and only recently made publicly available, suggests the company is exploring ways to take advantage of two-stroke engines, such as higher specific power, lower mass and a simpler design with fewer moving parts. As such, they plan to modernize them and place them in hybrid vehicles of the new generation.
Innovation in valves
The key problem with traditional two-stroke engines lies in the lack of a conventional valve system. Instead, they rely on openings in the cylinder walls for gas exchange, which are closed by pistons at the necessary moment. Such a design leads to a period of overlap, when the intake and exhaust channels are open at the same time, which results in the release of unburned hydrocarbons into the atmosphere. GM’s proposed solution targets precisely this problem by introducing an electronically controlled slide valve system, located between the piston and the cylinder wall, to provide more precise control of the opening and closing of the intake.
According to the patent documentation, the valve would be controlled by an electromechanical actuator, allowing the channel to be closed independently of the position of the piston. This would prevent the passage of unburned gases into the exhaust system, which would allow two-stroke engines to gain increased efficiency and lower emissions. The company believes that the incorporation of such technologies, along with electronic fuel injection and oil metering, could correct the shortcomings that caused these engines to be rejected in the first place.
While no information is currently available on when or how GM plans to implement this technology, the patent specifically mentions its use in hybrid vehicles. This suggests the possibility that GM is developing a new plug-in hybrid architecture, where a compact and powerful two-stroke engine would work in synergy with electric motors. If the concept is successfully realized, such a drive could possibly offer lower costs, better space utilization, lower weight and better performance compared to today’s plug-in hybrid units.