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).
Page discussing factors that affect petrol consumption, such as engine friction, speed, and carburetter settings.
| Identifier | ExFiles\Box 178\1\ img049 | |
| Date | 21th November 1925 | |
| - 3 - EXPERIMENTAL REPORT. EXPL. No. REF. Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}1/LG21.11.25. It will be observed what a large part engine friction and pumping losses play in increasing petrol consumption at slow speeds. As the piston friction usually accounts for from 65% to 75% of the total mechanical losses it will be seen that this item has an important bearing on petrol consumption under throttled conditions. The optimum driving speed for economy of the car tested appears to be lower than had been anticipated. Very soft tyres appear to absorb power in transmitting it as well as having a considerable rolling resistance, otherwise they would not affect the consumption so much at higher speeds. The optimum carburetter setting for acceleration is two notches too strong for maximum economy. Water temperature has quite an appreciable affect on consumption, reducing oil viscosity and so piston friction; this is one argument in favour of steam cooling. The use of increased ignition advance is quite impracticable as it would cause detonation under full throttle conditions. The benefit to be derived therefrom is also exceedingly small. For freak petrol consumption demonstration, there is little doubt that an EAC. car could be made to exceed 25 m.p.g. if driven in the correct manner with suitable adjustments. Actually when driven at an average speed of 36 m.p.h. in the normal manner, the car on which these tests were carried out, averaged 11.6 m.p.g. only. (contd). | ||