Spitfire RPM's

[Viper2000]

The Dh 20º prop is not the same as the Rotol 35º prop by any stretch of the imagination, even after the former has been converted to CS operation.

The Merlin XII has a higher supercharger gear ratio than the Merlin III which considerably increases the FTH for +12 psi operation, thereby making better use of 100 octane fuel, as well as improving altitude performance in general. However, performance below about 10,000 feet is consequently worse than that of the Merlin III due to the increased supercharger power consumption.

Since most combat during the Battle of Britain took place at about 18000' (which was the altitude the German bombers chose to fly at), the main effect of 100 octane fuel was to increase the RAF's climb performance, allowing them to make effective interceptions with shorter warning time, since even the Merlin XII couldn't deliver +12 psi boost above about 10500' static (so say roughly 12000' with 350 mph of intake ram).

Obviously this was important, but it affects the early part of the chess game, rather than the end game. Unfortunately, most people tend to see aerial combat in terms of the end game; but my online experience has shown me that in fact once the hard manoeuvring has started, quite often the outcome is already decided, the winner having initiated combat from a position of advantage.