David603, unless you are above best-turn-rate speed, downthrottling a Fw 190 seems to me to have no measurable improvement in sustained rate - in fact it seems to make it worse, as theory predicts. If you've got real evidence to the contrary, please provide it. Arguments about turn rates based on subjective opinions don't really get us far. I've managed to do some basic testing, using my autopilot, but this needs modification to do this properly. I'll try to get around to this soon, but meanwhile any other evidence will be welcome.
At a given sustained power setting, airspeed and turn rate, the AoA will be whatever it needs to be - that the Fw 190 gives better results at a lower AoA than the edge of the stall seems evident from testing - hence the fact that the best rate is faster than the minimum radius. With the Spitfire, the difference is less, suggesting that the best rate is at a higher AoA.
JG27CaptStubing, I see no reason why downthrottling would reduce turn radius, if you are already at best radius speed - again, I'd ask for evidence for this.
It is just possible that downthrottling is temporarily helping the turn through a reduction in torque and in gyroscopic forces (though this shouldn't be a factor with a constant-speed prop), but I can't really see how. As I see it, the best turn rate at a given speed will otherwise be constant, regardless of power setting - all changing power does is determine whether the plane will accelerate or decelerate at that point in time. As has been pointed out, in the real world, extra power increases the local airspeed in the prop slipstream, which should help a little in high-power turns, but I doubt that IL-2 models this effect (we need to be careful about distinguishing between 'real-world' results and IL-2 ones, while discussing this subject).
And as for 'magical ideas', I'd be happy never to see another word on the subject from Gaston.