The problem with the 2 strokes is purely lack of torque. These airplanes are so much larger and draggier, and the 2 strokes just do not have the torque. QQ flew the FI's a few years ago, and switched the electric, and now to YS. Yes, it will fly the sequence, no doubt, but there are going to be days when you simply do not have the power. The YS out turns the OS 1.40 by a wide margin when loaded. On a very hot day, you will simply not have the same power. On a cool day with light winds, you wont have any problems, but when the winds come up and the temperature goes up, you will be at a major disadvantage. The torque curve is not anywhere near the same. The OS produces very little mid range torque. I flew them for YEARS. I loved the way the motor ran, very easy to set up and bullet proof, but 3 years ago at the NATS when the winds were up and the temps were up, at the end of long verticals, the plane just didn't have the power to comfortable make the corners. Mike Hester experienced the same thing. My plane and his in 2006 were all under 10lbs, but with the drag of these new models they simply need more torque, this is where the electrics and 4 strokes have a significant advantage. I have no doubt QQ or any of the rest of the top guys could get the OS 1.40EFI's easily if that is what they WANTED to run. These guys don't fly stuff for no reason. At the level QQ and the rest of them are, they get to pick what they WANT to run. I loved my OS's, but they simply are under powered now. The OS 1.60 is a viable option. Unfortunately it is much heavier, but it will run the larger props and has more mid range torque. I still think it is at a slight disadvantage to the 4 strokes and the electrics, but it is significantly more powerful than the 1.40RX. When I say underpowered, I do not mean what the engine will turn a certain prop on the ground. I mean when the airplane is in the air and under load, does the RPM drop, or does it stay the same. You can hear the differences in the OS 1.40's at the top of long climbs. Mike Harrison has been running the OS 1.40s for years here, and I have seen him several times being very marginal on power. I believe he is actually switching to the OS 200 for next year.

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