3 ms·
Two-strokes are extremely dirty, due to blow-through of the fuel-oil mixture, incomplete/less efficient combustion due to crude fuel metering, and inability to
by kortex 4y ago
Two-strokes are extremely dirty, due to blow-through of the fuel-oil mixture, incomplete/less efficient combustion due to crude fuel metering, and inability to use conventional catalytic converters (due to fouling from the above two points). But they do afford roughly double the power-per-RPM of four-stroke engines, and a further power-to-weight multiplier due to their simpler design.
AFAIK there's nothing mechanically stopping you from scaling a 2-stroke, but it would very quickly render the immediate area noxious.
But they are simple, lightweight, and easy to shrink.
This is actually a really important point as we are trying to clamp down on VOC/NOx emissions. Ignoring CO2, two-strokes emit way more emissions than cars per unit work. But a 4-stroke engine, in addition to expense, does not lend itself to tools like chainsaws. In theory this engine could fill that niche.
- davidbanham 4y agoThe rotary in the article is a 2 stroke design, by my understanding. Fuel injected 2 strokes have been around for years now. In saws, the Stihl 500i. Scaled 2 stroke engines, both with and without fuel injection, have also been around some time. The KTM 300 XC is a very modern example with 300cc displacement, so the same general category as the one in the article. Modern outboards on boats go even bigger. Yes there’s a push on at the moment to retire the fleet of small 2 stroke engines in older garden power tools. Emissions controls have been tightening up on new tools over the years. Electric tools are rapidly displacing them with lower maintenance requirements and less noise. There’s a lot more to 2 stroke engine development than just saws and lawnmowers from the 80s, though.