ORIGINAL: Sandman
- 4 strokes have a lower maximum RPM but more power, meaning that you can use a larger prop which will turn slower giving the same overall performance.
Often repeated, though not QUITE true as stated, making things very confusing to the novice.....
4 strokes do have a lower maximum RPM as indicated.
However to achieve the SAME OVERALL PERFORMANCE you typically have to go with a higher displacement four stroke engine, to achieve similiar power levels.
e.g.
A 2 stroke .61 SuperTigre produces about the same amount of power as a .91 four stroke O.S. engine.
To use that "larger prop" you need to increase the displacement of the four stroker.
Four strokers tend to develop more torque at lower RPM's given the displacement difference... The .91 4S will max out at lower RPM, with good thrust. The .61 2S will need to spin much faster to achieve it's maximum power output.
The former TENDS to produce better thrust at less speed, while the latter more speed, but less thrust.
Of course you can adjust for all of this with proper prop selection.