Technical report analyzing the effects of hot and cold air intake on carburettor performance and mixture temperature.
| Identifier | ExFiles\Box 123\1\ scan0019 | |
| Date | 22th January 1940 | |
| -2- Rm {William Robotham - Chief Engineer} /FAS.3/MH. {M. Huckerby} 22.1.40. (2) With a fully expanding type of carburetter the fuel at the jet is maintained at a lower pressure than is the case with the fixed choke type and it is hence in a condition more agreeable to vaporization. (E) is a fundamental difference and nothing can be done about it. To remove the disadvantage (1) either the air, the petrol or the mixture must receive more heat. It is not practical to heat the petrol due to the vapour lock troubles which would ensue. To heat the air is difficult and cumbersome. It has been tried by several people, notably Buicks, and abandoned in every case. The difficulty is in getting air hot enough to stand a big temperature drop through the carburetter. The following figures were obtained using the hot air intake pipe built by Rm {William Robotham - Chief Engineer} /Wym. {G. Harold Whyman - Experimental Manager} for 12.B.V. They were obtained with the engine running light at 1,000r.p.m. in the Garage. AIR INTAKE TEMP. measured directly above carb. with glass thermometer. MIXTURE TEMP. IN PIPE measured with N & Z thermo-meter inserted vertically through the petrol drain hole. CASE 1. | CASE 2. | CASE 1. | CASE 2. HOT AIR INTAKE. 38°C | 48°C | 7.5°C | 11°C COLD AIR INTAKE. 22°C | 24°C | 4.5°C | 7°C Thus it will be seen that the mixture is only going to benefit by 15-20% of the increase in air temperature. The fact of 12.B.V. refusing to respond to hot air treatment on the road is offset by the knowledge that this hot air never gave a mixture temp. rise of more than 6°C, which with an outside air temp. of -5°C could be expected to do little to aid carburation. | ||
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).