4 strokes lack power.

Mike McConville flies a Midwest AT-6 powered with a Saito 170 R3 radial. According to Mike, "This was true when 4-Strokes were first introduced to RC in the early 1980s, but today 4-strokes provide extraordinary power. Because they produce more torque than 2-strokes, "4-stroke power" has a unique feel. The models fly at a more constant speed, go up with a more authoritative feel and come downhill slower". Pete Goldsmith chimes in on this one, too: "I absolutely agree about the torque. What 4-strokes lack in top end horsepower, they gain in torque. Why is torque so cool? Well, you can turn big props, generating more propeller efficiency and hence gain more thrust. A side product of this is that bigger loaded props turn less RPM and that is the best way to keep noise down. Plus, with lower RPM and more propeller efficiency, the engine will have a better fuel efficiency. The lower RPM is also better for life span of the engines and the life span of glow plugs.