First of all, sorry to have come off sounding so crude at before. Let’s start with me. I am a good friend of the guys at Aeroworks and with that am good friends with many top-notch IMAC pilots, including Chip. I have owned a few 50cc size airplanes and have flown everything else. That includes all the engines that have been discussed here. I flew the AW 31% 540T with both a 3W 75 and a zdz 80 along with a H9 Cap with the zdz 80. My impression was that the zdz was a top end engine. Powerful? Yes, but torquey? Not really. As compared to the 3W with has ungodly torque and a high top end. This is at least my preference for torque rolls and hanging and such. Not to say that this is right. The bad thing is that both engines shake like crazy. The 3W more so than the zdz. But after all, they are huge single cylinder engines. After flying those zdzs, I was very unimpressed. They have good top end power but nothing in the mid range. Therefore, that is why I recommend the 3W hands down.

And 3W torque is when you can have the airplane idling on the ground, punch the throttle, and have the left wing tip almost hit the ground!

That is what I call torque!