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).
Issues with carburettor intake air temperature and proposed solutions for various engine types.
| Identifier | ExFiles\Box 159\5\ scan0072 | |
| Date | 23th October 1940 | |
| Ev.{Ivan Evernden - coachwork} from Rm.{William Robotham - Chief Engineer} c. Jnr.{Charles L. Jenner} c. Rm{William Robotham - Chief Engineer}/Sym. c. Rm{William Robotham - Chief Engineer}/Col. c. Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation} c. Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden} Handwritten: Minos to Testers Rm.{William Robotham - Chief Engineer}10/ML.23.10.40. AIR TEMPERATURE OF CARBURETTOR INTAKE. We have recently found that on our engines, we cannot set the carburettor for maximum economy because, under winter conditions, with low under bonnet temperatures, the air entering the carburettor is too cold. The trouble only arises on cars that are not fitted with thermostatically controlled radiator and shutters. It is aggravated on 8-cylinder cars, where the induction pipe is long and, on some of our 6-cylinder cars, due to the fact that the engine is over-cooled. We anticipate that on the small 4-cylinder engines that we are contemplating, the situation will be eased because of the very short induction pipe and also because the engines will be working at a greater percentage of their full power all the time and in consequence, the under bonnet temperature will be relatively higher than on the senior range of cars. However, we think that we should definitely design our radiators so that the car is not over cooled, the radiator with a pressure valve to take care of the rare occasions when the car will normally overheat, and make the matrix relatively deep, so that the under bonnet temperature is greater than it would be for a thin matrix of greater frontal area for any given quantity of heat dissipated. We should be glad if Rm{William Robotham - Chief Engineer}/Col. would make some recommendations for the 4 1/4 and 3 1/2 litre Bentley radiator matrices, based on these objectives. To avoid loss of volumetric efficiency in hot weather, a thermostatically controlled by-pass to the outside air, could be provided to the carburettor intake on the bigger models. Will Ev.{Ivan Evernden - coachwork} please consider some sort of scheme for this. Rm.{William Robotham - Chief Engineer} | ||