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 tests and experiments on various vehicles to improve fuel economy.
| Identifier | ExFiles\Box 147\5\ scan0118 | |
| Date | 12th January 1937 | |
| 8 1249 Sg.{Arthur F. Sidgreaves - MD} from Rm.{William Robotham - Chief Engineer} Hs.{Lord Ernest Hives - Chair} c. to E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} c. to Mx.{John H Maddocks - Chief Proving Officer} PETROL CONSUMPTION. Comparative tests between the Chevrolet and the 25/30 showed that the Chevrolet was the more economical. Tests show that this was partially due to the vacuum ignition control. We, therefore, carried out tests fitting this device to the 25/30, and the attached Report shows the results obtained. The nett result was an increase in consumption of 1 1/2 m.p.g. at an average speed of 46 m.p.h. We have carried out previous tests on the vacuum ignition control on the Graham Paige which we had, and the advantage appeared to be negligible. We observed that the general tendency of American cars was to dispense with this device, though two years ago its use was almost universal; this may, of course, be due to basic alterations in combustion chamber shapes, but we intend to get the latest information on American practice before we go into production with any such scheme; in the meantime, we are repeating the tests on the P.III. We have also carried out experiments on the P.III to improve the consumption of this car. We have realised for some time that owing to the fact that we use a different fuel feed for the Americans, the needle valve mechanism of the Stromberg Carburetter has restricted our petrol delivery at high speeds, and, in consequence, the float chamber level has not remained constant. The nett result of this is that to overcome the low level at high speeds, we have to use a jet which is unnecessarily strong at intermediate speeds. Tests show that if we correct the trouble by altering the float lever ratio, we can increase the petrol consumption at an average speed of 50 m.p.h. by rather more than 1 1/2 miles to the gallon. The matter has been taken up with the Design Department, and an experimental carburetter is being sent out to France with 35-EX to confirm the results obtained in England. We are hoping that on the Continental car if we take advantage of this modification and the suction ignition control, we shall, owing to the fact that this car will also have a higher axle ratio, higher compression and much less total weight, be able to get a better range than on the standard P.III, and yet carry 10% less petrol. Rm.{William Robotham - Chief Engineer} | ||