johndavis

was wondering the positive's and negitives of both.

jester_s1

In a nutshell...

2 stroke positives: More power for engine size and weight, simpler operation, lower price, higher RPM performance for high speed flight
2 stroke negatives: peaky torque curve, less fuel efficient for the horsepower it makes, sounds like a constipated mosquito

4 stroke positives: more torque for turning larger props, accelerates faster and more smoothly, more fuel efficient, sounds more like a real airplane engine
4 stroke negatives: costs more, often heavier for the same amount of power, must be roughly 25% bigger to make the same power, valves have to be adjusted right, tuning requires a little more skill, tops out around 10k rpm so has a much smaller RPM range.

Gray Beard

My Feedback: (-1)

Depends on the brand of the engines too. I don't see a negative with either except price. I just like four strokes better then two strokes, good four strokes. I have found a cheap two stroke I like a lot too.

JohnBuckner

My Feedback: (1)

Entirely dependant upon the mission of the airplane and I do use and fly a wide variety of just about every power system type that has ever been used, but for basic sport flying I much prefer the "Constipated Mosquitos"

John

jetmech05

I think jester nailed it

jester_s1

I agree with you JohnBuckner. The 2 stroke is really the best power system for most planes simply due to its light weight and big RPM range. 4 strokes make sense when you need a lot of torque to spin a big prop (like on 3D aerobats) or want a full scale sound.

johndavis

thank you for your great responces. im going with the 2 stroke . i have experience with the 2 stroke engines i race rc cars. i have never been around the 4 strokes i will try one of them later on after i learn how to fly. im going to build my first airplane for the experence of doing it. and building your own will teach me how to repair it after i crash it a time or two. lol