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).
Carburetter air intake temperatures and their effect on fuel supply efficiency and overheating.
| Identifier | ExFiles\Box 24\5\ Scan259 | |
| Date | 9th July 1930 | |
| -2- Hs{Lord Ernest Hives - Chair}/Rml/MJ9.7.30 contd. temperature of the air intake to the carburetter. With an atmospheric temperature of 24°C. the air intake reached 50°C. at 75 M.P.H. As soon as the car was stopped this temperature exceeded 60°C. with unventilated bonnet. It seems feasible that the vacuum pump would fall off in volumetric efficiency at these temperatures due to the low boiling point of petrol giving us a worse result than can be obtained on the road wheel dynamometer, where everything is shielded from the exhaust and kept as cool as possible with the bonnet off etc. We are continuing tests to see exactly what does happen. We have given prominence to this question of fuel supply because we think it is likely to cause weak mixtures at high speeds which, we shall shew later, have a bearing on overheating. Actually, we have not recently had any reports of fuel shortage on our 10,000 miles tests, and have only a few isolated complaints from customers of the trouble, which shews that full throttle can seldom be held for three minutes on the road. It is, however, clear that as we are so much on the border line, any variation in the vacuum pump or autovac efficiency will cause trouble as will any slight air leaks on the suction side of the pump such as in the two-way tap or in the soldering of the tank filter tubes. Trouble caused | ||