Góð (stutt) grein um tuning á heli-mótor

[benedikt]

Why your needles and Curtis Youngblood's needles shouldn't necessarily be set the same

If you get a chance to watch Curtis Youngblood, Jason Krause, Todd Bennett, Dave Storey, Gary Wright or any of the other top notch pilots fly, notice that, once they go into idle up, they are going from one maneuver to another without hesitation. They don't normally have to adjust altitude or position between maneuvers, and, if they do, they make it look like it's part of the routine.
These guys usually have their engines tuned really well...for their style of flying. They keep the rotor disk "loaded" constantly. That means they have a lot of pitch in the blades, whether it's collective pitch, cyclic pitch or a combination of the two. You don't see them hovering or making slow descents in idle up. I don't mean they are overloading their engines, just keeping them "under a load". These guys are very good at collective management. They only use full throttle when it's necessary.

Going back to some basic engine facts might help you understand why this is important. Take a typical, broken in, .61 two stroke model engine and put it on a test stand with a 12x6 prop. Adjust it for max rpm and note the settings and rpm. Now take the 12x6 off and put an 11x5 on it. What happens if you leave the mixture screws in the same position? It'll probably destroy itself in short order because now, it's running way too fast, way too lean, and gets very hot very fast. The engine just isn't designed to be run without the proper load at that mixture setting. You could richen the mixture, which would reduce the rpm and keep the engine cool. It certainly wouldn't be making as much power, but at least it isn't going to blow up.

The balance between the pitch and throttle curve, the speed of the throttle servo and how fast the throttle stick is moved all come into play. These guys set their machines up for their style of flying. Curtis, for one, realizes this when he's helping someone with their model. When he gets done tweaking on it, he'll usually ask you to fly it yourself. Don't decline. Go ahead and fly it the way you normally fly. He'll be listening to the engine and if he sees that you are constantly unloading the disk, he'll probably suggest richening it up a little. The guys I've mentioned above are all aware of this and will more than likely make sure everything is okay before they walk away. However, if, after having your engine tuned by one of the big dogs, you notice that it seems to be over speeding a little or running hot, at least you'll know why.