can't speak to what the actual ratio is for your engine. However, I do have experience with the two different ratios for the 540. A gov NEEDS to be internally setup for the engine's ratio in order to meet it's design goals (adjustments usually related to speeder spring tension); This comes straight from hartzell. While the ext speed adj screw can get these units to govern at 2700 in many / most cases, a ratio mismatch WILL mess with the low RPM point at which the governor can still control the prop. You will also be at the end of the adjust ability range of the speed adj screw. Some govs are fixed at a ratio and others, like the hartzel S series, have internal adjustments that can be made to accommodate different ratios. I did that on my gov, but need the manuals, as you are disassembling spring and moving staked pins. My guess is that the whirlwind is also adjustable, but needs to go back to a prop shop to be adjusted IF it was originally set up for a different gear ratio.
Freemasm / Bob, there are a set of flyweithts and these exert a lnear (with gear RPM) pressure against a speeder spring. The spring ultimately apples a semi- linear action to the portion of the gov driving oil pressure on the output. Therefore the spring properties greatly affect the linear relationship between input gear speed and output oil pressure. In the hartzell, you can clock a cam that increases spring pressure pre-load, and this is how the gov is set up for the gear speed it will be seeing from its engine mate. The spring rate will work across different ratios by design, but the minimum governing point is set by the speeder spring pre-load and NOT the springs rate. The speeder spring is internal, sitting right over the flyweights. I am NOT referring to the tensioning spring on the outside of the gov, which by the way, is also part of the tension arrangement and why they have a special procedure for setting it's preload.
While not wanting to start a debate, I am pretty confident that the gov moves the blades with pressure, not flow. Yes, you have to have enough flow to maintain that pressure with all of the bleed off, but ultimately it is pressure that moves the piston in the prop. I believe this is basic hydraulics. You could have 1000 GPH at 1 PSI and those blades WILL NOT move. My garden hose flows a LOT of water but can't do any work. I put a restrictor on it to realize the 50 PSI head pressure and now I can start scraping debris off the pavement. Really not any different than the oil pressure regulator in our lyc's. It controls pressure, NOT flow. Yes flow does impact the precision of it's regulation, but across a pretty wide range of flow it holds a relatively constant pressure. But to your point, once the pump volume falls too low at idle, the pressure drops as it has fallend under the regulators control window.
Larry
