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).
Tests on petrol consumption, rolling resistance, and engine friction.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan153 | |
| Date | 12th June 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. -2- Expl. No. REF: Ha/RmL/LG21125 during the test, the latter being quite independent of the speedometer. From these two readings the petrol consumption in miles per gallon was calculated. In this method the effect of variations in road surface or gradient and wind are as far as possible eliminated. The tests are carried out reasonably quickly and the extent of small variations in the performance of the car can be detected. For estimating the proportional value of rolling resistance, engine friction and oil churning transmission losses, the car was run with the rear wheels jacked up, in gear and in neutral, the consumption for a given time being measured, a fixed speed being maintained by means of revolution counter or speedometer. RESULTS OF TESTS. These tests were carried out with a view to substantiating the theoretical observations on petrol consumption which have previously been made. The earlier report remains a general review of automobile fuel economy. The curves obtained are more or less self-explanatory. It must be remembered that the effect of any alteration on the car's petrol consumption is magnified considerably by carrying out the tests at slow speeds without acceleration. 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 contd :- | ||