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).
Petrol consumption, focusing on the negative effects of acceleration and the use of four-wheel brakes.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan163 | |
| Date | 12th June 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. -8- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}/LG2.11.25 50 m.p.h., the petrol consumption will be doubled. ACCELERATION Acceleration is bad for petrol consumption. A lively car is one that has a large amount of power in reserve. This means that under normal running conditions, the engine will be performing at but a fraction of its full load which we have shewn is bad for economy. If the owner demands a better consumption and is not interested in acceleration, a higher geared axle will produce the required result (see graph 11). If a good consumption is required, the car speed should be maintained, as far as possible, constant. As an example, if two owners averaged 30 m.p.h. and one indulged in violent braking and acceleration while the other endeavoured to keep close to the 30 m.p.h. speed, we should expect the petrol consumption of the latter to be at least 20% better than the former. The reason for this is obvious because 9.5 HP. is required to drive the car at 30 m.p.h. but 60 HP. will be developed at this speed when maximum acceleration is being indulged in to the detriment of economy. In addition, over-rich mixture must be supplied to the engine when accelerating to prevent choking. FOUR WHEEL BRAKES. Owners have often noticed increased petrol consumption with four wheel brakes. The obvious reason for this is that they hang on to full throttle opening up to the last minute when these are fitted, instead of making a contd :- | ||