This is a piece by my good friend Professor Rick Hillum in response to comment posted to the site as to why Spitfires and Hurricanes were equipped with carburettors and the Messerschmitts with fuel injection:
Power output from an engine equates to the sum of a considerable number of components that include things such as compression ratio, flame angle, burn duration, air temperature, combustion timing and temperature, fuel humidity, Supercharger boost pressure for a given air/fuel ratio and so and so on. One of these parameters is the amount of fuel for a given volume of air (air fuel ratio) and this on the Merlin was varied automatically at differing altitudes to help maintain the required mixture ratio.
In a Carburettor, there is drop in fuel temperature due the air passing through the venture (caused by the Bernoulli’s principle for those that want to know more), resulting in an increase in fuel density for a given volume. Too lower drop however results in the formation of carburettor Ice, and as any modern piston engine pilot will tell you. This will result in either a significant power reduction or totally stopping the engine if this is allowed to happen. However, the RR logic and design philosophy was simple and justifiable, the greater the fuel density =the great the power. RR also had a continual program of improving the performance, including areas such as the supercharger.
In the cat and mouse game of aircraft performance, and as part of this on-going review, Rolls Royce did look at fuel injection so I understand (not that I am aware of them having a credible injector system), but had dismissed it as it provided lower fuel density per given volume and thus less power output. This is at a time when every ounce of power counted. However the disadvantage, as James has already identified in his book and Battle of Britain program, the carburettor in the Merlin, could not cope with negative G and caused the engine to rich cut when experienced. It was not until 1941 that Miss Tilly Shilling, with a clever little washer type device, helped considerably but not totally solved, the fuel and float level rapidly raising and dropping in the float chamber that caused the engine cut problem.
The injected DB601range as fitted to the 109 had a different combination of components to achieve similar power levels and consequently was able to make use fuel injection and its advantages. Fuel injection provided precise metering of the correct amount of fuel and precisely the correct time it is required and does not have a carburettor float that is sensitive to negative G forces. The BD fuel injectors would automatically adjust or meter the fuel, optimising the fuel/air ratio with altitude, engine revs and with supercharger boost pressure. Indecently, the more powerful modern aircraft engines also tend to use fuel injection for the some of the same reasons and it is hard to find any car that is not using fuel injection today.
Additionally there is a lot on the web about the RAF having a significant advantage because they had 100 octane fuel, but taken in balance of the above, it is just another component in the power output formula (albeit significant to the RAF at the time). Further to this point, not all aircraft engines could cope or were designed to cope with 100oct fuel, It could cause significant issues such as hotspots in the combustion chamber burning holes in pistons and valves through effects such as pre-detonation, overheating pistons etc etc. 100oct allowed the RAF to operate at higher or double the supercharger boost pressures without causing pre or post detonation, significantly improving the performance of their aircraft at the time.