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).
The testing and performance issues of an 'IMCO' Autopulse fuel pump fitted to chassis 9-EX.
| Identifier | ExFiles\Box 41\1\ Scan025 | |
| Date | 13th September 1926 | |
| COPY. Y3800 To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/AJL. c. to BJ. Wor.{Arthur Wormald - General Works Manager} c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} c. to OY. Hs{Lord Ernest Hives - Chair}/AJL1/LG13.9.26. 'IMCO' AUTOPULSE FUEL PUMP. This pump has been fitted to chassis 9-EX and has run 835 miles. It was sent to us by Springfield as an alternative to the vacuum feed. It has not been entirely satisfactory in service. On one occasion when changing down from top gear to a lower gear on a hill that necessitated full throttle, the pump failed momentarily to supply the required amount of petrol to the carburetter. This is the only actual failure during the test. It has been noticed that the carburation has been extremely erratic on this car ever since the Autopulse was fitted: this appears to be due to the pump not keeping as constant a petrol level in the carburetter as does the Autovac. The carburetter petrol levels comparing the Autopulse and the Autovac systems under similar conditions were found to be as follows :- AUTOPULSE - Stationary 1.0" - light running 1.3" to 1.6" AUTOVAC - " 1.2" - " 1.7" (The figures given are the measurements from the float chamber top face to the petrol level in the jets). The Autopulse increases the level under both conditions and does not provide a constant level under light running conditions. A small delivery valve in the Autopulse unit is expected to control the amount of petrol delivered to the float chamber, this is not sufficiently sensitive to ensure a constant speed. Under these conditions its failing is very pronounced, the pump should work perfectly regularly as it is called upon to supply a regular quantity of petrol, whereas it works spasmodically - for short periods it delivers no petrol at all (the carburetter petrol level falling in consequence), and then suddenly it works vigorously to make up the leeway, in consequence of which the petrol level in the carb. is suddenly raised to higher than normal correct level, before the pump ceases to work again. This produces very uneven carburation under light running conditions. The Autopulse pump is also extremely noisy in operation, this factor alone prohibiting its adoption as a std. accessory. Hs{Lord Ernest Hives - Chair}/A.J.Lidsey. | ||