2-Speed, 2-Stage, Supercharger
As asked about in another forum, here is a brief run-down on the modeled Merlin V-1650-7 engine supercharger, as included in "Little Friends".
First off, this feature requires you to have Acceleration installed, in order for the supercharger modeling to work (if you don't have Acceleration installed, there are alternative flight dynamics files contained for use).
From at sea-level, you will be able to achieve 67-in MP, at full-throttle. With the engine damage modeled in, however, you won't be able to run more than 61-in MP, for more than 5-10 minutes, before your engine begins failing. As you ascend to altitude, eventually full-throttle will only allow you to maintain 46-in MP (max climb power), by the time you reach 17,500 ft. At the 17,500 ft mark, high blower automatically switches ON, and you can see it, feel it, and hear it, all at the same time. When high blower comes on, you will suddenly get a great boost in power, now allowing you again to attain 67-in MP at full-throttle. A red-indicator light also comes on, to let you know that the supercharger is in high blower (though you will know otherwise as well! : ) ). When this happens, you of course have to adjust the throttle back to proper settings, so that you won't be over boosting the engine. The extra power you get at high blower, will then allow you to climb up and perform at regular combat heights of 25,000-30,000 ft. If you are lucky, and have the aircraft very lightly loaded, you can even just barely achieve the aircraft's highest recorded service ceiling, of roughly 41,900 ft, by which point you will be able to achieve about 28-in MP at full throttle.
As discussed within the flight manual portion of the Little Friends user guide, max-recommended power at take off is 61-in MP. However, 'normal take off' power is as low as 46-in MP! For me, I usually use either 50-in MP, or 55-in MP, depending on the aircraft's loading, which is more than sufficient.