There's a wide assortment of "constants" that affect the simulation of the helicopter.
They are adjustable on this screen (within range limits), and are described individually here.
Pinion Gear Teeth
As on a real 450, a higher pinion tooth count will give you higher head speed, and less torque. The peak RPM will be higher, but it will drop more under load.
Maximum Collective
This is the collective pitch in degrees at full stick deflection. Higher pitch produces more lift at a given RPM, but will also produce more drag, torque, and result in more RPM drop.
Rotor Inertia
This is essentially the blade weight. Higher inertia makes the rotor change speed more gradually. This number is mainly useful for making autorotations behave like they do on your real 450.
Motor kV
As on a real 450, a higher motor kV will give you higher head speed.
Battery Voltage
This is the fully charged pack voltage for the simulated battery. The simulated battery has infinite capacity! It never goes down, never needs charging, never puffs, never over heats... And it survives ALL crashes. Where can we buy these? I only need one!
Motor Torque
This is the motors torque constant. It controls the amount of torque the motor produces, proportional to the difference between the rotors actual RPM and the steady state RPM that would result from the throttle setting, battery voltage and the motor kV.
A higher number here will produce less bogging of head speed under load. It will also result in more rapid speed changes from throttle setting changes.
If you make this number large enough, it will behave like a governor. You can use a flat throttle curve, and a high torque number to achieve a nearly fixed RPM.
Aerodynamic Drag
These three numbers control how much drag the helicopter sees due to motion through the air. Drag is separated into the three different axes: along the helicopters axis, side to side, and vertical.
Control Response
These three number control how rapidly the helicopter responds to control input, in the three different axes. These are the sensitivity at maximum travel controls. There are also exponential rate settings available on the Model->Expo Rates menu.
Lift at full collective
This is the amount of lift produced by the main rotor at 12 degrees pitch. A higher number here implies a more efficient rotor. This number does NOT affect torque! If you want to add/reduce your collective response POP beyond what you can achieve with headspeed and collective travel, this is the number to tweak.
Ground Effect
This is the degree to which ground effect influences lift. The simulated ground effect takes place at heights less than one rotor span above the ground. A higher number results in stronger ground effect. The default is set to simulate flight over pavement, which produces more ground effect than grass.
Mass
This is the helicopters mass in kilograms.
Side Thrust
This number controls how much side force is produced by the tail rotor to counteract the main rotor torque. any new pilots are surprised to see that their helicopter needs to be tilted slightly to one side to hover in one place. The tail rotor obviously pushes sideways. The tilt is necessary for the main rotor to produce a counteracting side force in the opposite direction.
Translational lift
When the main rotor is moving horizontally (translating), its lift is increased due to the increased airflow through the rotor. This number controls the degree to which the translating motion increases lift. Higher numbers produce higher lift increases.
Translational pitch up
When a main rotor is moving horizontally (translating), its natural tendency is to pitch up. Forward motion will produce nose up attitude. This effect is largely (or completely) eliminated by the stabilizing control rotor, high head speed, utilized in 450 helicopters. So the effect is very small in most 450s. This number controls the degree to which the translating motion produces pitch up. Higher numbers produce higher pitching tendency. Note that the same effect occurs in sideways flight, and is modelled in HeliSimRC.
Gust pitch up
Similar to translational pitch up, except this motion is in response to a wind gust. Again, its typically quite a small effect on 450 electrics. Higher numbers produce higher pitching tendency.
Cyclic instability
When hovering, a typical 450 electric will tend to randomly wander off to one side or the other. Once it begins motion in a certain direction, it will continue that way. This number controls the degree to which HeliSimRC models this instability. 0.0 is useful for learning. 0.1 feels about like a real 450.