GM wants to bring back the two-stroke engine – Jalopnik

Unless you’re really into dirt bikes, you probably haven’t touched a two-stroke in decades – if you ever have. These mechanically simple engines combine the four strokes we all know and love into just two, so suck, squeeze, pop, blow becomes righteous suck/squeeze And clap/clap. Two-stroke engines explode every time the cylinder reaches top dead center, twice as often as any modern street engine, yet we never use them anymore (turns out all those extra ignitions result in extra emissions). But it looks like General Motors, of all companies, wants to change that.

A recently unveiled patent from the company focuses on new technology for two-stroke engines, with a specific focus on use in ‘hybrid electric vehicles’. Still, GM’s patent doesn’t appear to fully solve the emissions problems that took two-strokes off the road in the first place. Instead, the patent is for a new valve system designed to reduce piston ring wear, extending the life of traditionally maintenance-heavy engines.

These linear valves likely allow for somewhat finer control over valve timing, as they can move at least somewhat out of sync with the piston, which isn’t really adjustable in the simplest iterations of a two-stroke engine. Yet two-stroke engines have had valves before simple diaphragm valves to the rotating locks of Rotax fame. The bigger problem with two-strokes on the road is the sheer volume unburned hydrocarbons that they spew out of their exhausts, and this new valve arrangement doesn’t seem to solve that – GM shows that the valves move simultaneously on the intake and exhaust sides, a synchronization that makes it possible cross-flow extraction to maximize the new charge, but doesn’t address the emissions elephant in that particular room. Maybe GM has more tricks up its sleeve and a plan to make two-strokes EPA compliant again, but I wouldn’t count on this unique patent to deliver on that ring-ding-ding sound coming soon to your local parking lot.