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).
Test report detailing modifications and performance comparisons of petrol delivery through different filter and tap hole configurations.
| Identifier | WestWitteringFiles\Q\December1926-January1927\ 131 | |
| Date | 31th January 1927 guessed | |
| contd :- -2- 'A' and 'B' holes and also if 'C' is opened out to .3125" the metal at this point becomes very thin and would fracture if the petrol pipe union nut were tightened up excessively. The maximum improvement that can be made to the existing tap is to open out the holes 'A' to .250" and the hole 'B' to .3125", under these conditions the Autovac delivers 3.5% less petrol than through the old type filter. This alteration has been instructed on all existing and future filters of this type. We do not imagine that the very small difference in petrol delivery would ever be apparent under road conditions. The following test gives the improvement due to opening out the tap holes and also shews the difference in petrol delivery by the Autovac when the petrol is sucked through a plain pipe as compared with the old and new type filters. The test was carried out at 1500 r.p.m. full throttle. The petrol was lifted 32" through a 1/4" bore pipe 6 ft. long, the height 32" representing a petrol tank containing 6 gallons of petrol and the car standing on the level. Induction pipe depression 2.1" mercury. | | Condition of test. | Time for delivery of 1 pt. (secs.) | |---|---|---| | (1) | Petrol sucked through a plain pipe 6 ft. long. | 86.5 | | (2) | Petrol sucked through old std. filter attached to pipe 6 ft. long. | 88.5 | | (3) | Petrol sucked through a new type filter as originally designed. | 101.8 | | (4) | As 3, but holes 'B' increased to to .3125" diameter. | 95.7 | | (5) | Holes 'A' increased to .250" dia. | 91.5 | | (6) | Holes A, & B, & C. .3125" dia. | 88.5 | | ||