ORIGINAL: Mr67Stang
ORIGINAL: Gray Beard
That's pretty basic old school thinking about the power difference between the two and four strokes. There is still some power difference but the four strokes have gotten a lot closer these days to the power of the two strokes, it isn't anything like it used to be with the old fours. The smallest four stroke I have today is the OS .91 and it pulls the same plane every bit as well as my two stroke .91. Isn't as fast but it has about the same power.
I think you may be confusing power and torque. You can spin a larger prop on the four srokes because they have the torque to do so, so your .40 4 stroke can spin about the same prop as a .40 2 stroke but that 2 stroke will spin it at a higher RPM (power).
Right... hence the comment about not pulling as fast. Manuf reccommending a .60 2s will also require a .90 4s. However I am new to 4s myself and am currently breaking in a .52 and 70. I'm planning on putting the .70 in a GP .40 cub with a clipped wing. It reccomends a .48 to .80 4s so I think it will be a real nice match for scale aerobatics. Not sure about the .52 yet.