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).
Methods for achieving and measuring excellent petrol consumption.
| Identifier | Morton\M22\ img125 | |
| Date | 30th September 1920 | |
| R.R. 199 (250T) (SD676 19-7-17) MP 180865 Contd. -2- Hs{Lord Ernest Hives - Chair}2/LG30.9.20. Perhapsthe biggest factor as regards obtaining excellent petrol consumption is the way in which the car is driven. The car should be driven so that at no time a brake is ever used. This applies to using the engine as a brake as well as the mechanical brakes. This means, on a down grade, the clutch is held out and the engine stops - it is started again when the speed of the car has dropped by letting in the clutch. Our consumptions are measured going out and back along the same road so that whatever advantage we get running down hill we have to climb on the return journey. We consider the fairest way of measuring petrol consumption is to put a certain quantity of petrol in the tank and for the car to go as far as it will on an outward journey with no restrictions made on the way the car is driven as long as the average speed is maintained. When the petrol is used up on the outward journey a similar quantity is put in the tank for the return journey and the consumption measured again. We consider that the two things a customers is interested in are miles per gallon and average speed. If it is possible to make a car to run along and average 25 m.p.h. without the engine running, it seems quite unreasonable to insist that the engine should be kept running simply to burn petrol. On the London to Edinboro' run on which we averaged 24 1/2 miles to the gallon, the R.A.C. insisted that the engine should be kept running the whole time, this meant that when coasting down hills the engine was running and simply wasting petrol. On a later run made by the Napier Car, it was mentioned that the engine of the car was stopped so | ||