We’ve seen engines that turn cylinders on and off but how about engines that switch between 2 and 4 stroke operation on the fly? The engineering firm, Ricardo, has developed a prototype of an engine that does exactly that, they call it the 2/4Sight. With careful design of intake and exhaust ports plus a control system that manages the direct fuel injection timing, the electro-hydraulic valve timing and intake boost, they pulled off what seems to be quite a feat of engineering.
The end result is projected performance from a 2 liter engine equal to a normal 3.5 liter engine, fuel savings of 27 percent and CO2 emissions are reduced as well. The added benefit is still being able to use an internal combustion engine which means all of the necessary fuel supply infrastructure is already in place.
Not only does there seem to be a lot of life remaining in the internal combustion engine, after seeing the JJ2S X4 a few days ago, it may also indicate 2 strokes aren’t quite dead yet, either. Now, if they can just scale this down to motorcycle size …
Diagram of 2 stroke cycle below: