From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Comparison of Measuring and Moving Float type Autovac fuel systems and their performance under different conditions.
| Identifier | ExFiles\Box 40\4\ Scan212 | |
| Date | 2nd February 1927 guessed | |
| - double that supplied per stroke by the Standard unit. The Measuring Autovac is fitted with a third valve in addition to the usual suction and air valves; this valve is fitted to the petrol port and is closed by a special toggle mechanism at the same time as the suction valve is closed and the air valve opened. The object of the petrol valve is to ensure that no petrol enters the Autovac after the float has completed its stroke i.e. that no more than .002 Gallons is drawn in per stroke. It also serves as a non return valve, preventing the petrol in the pipe to the rear tank from falling back by gravity every time the Autovac vacuum is released. Fig I shows the results given by the above two types of Autovac, under full throttle conditions, as compared with the standard Autovac. The moving float type of Autovac is far superior to the standard or a measuring type; the increase in petrol delivered becoming greater as the induction pipe depression rises, being approximately 40% more efficient at an induction pipe depression of 2.7 in Mercury. The Measuring Autovac does not give the results one would expect; although the petrol drawn in per stroke is greater than on the standard Autovac, the delivery under small induction pipe depressions is actually less, but improves as the depression | ||