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).
Report comparing an American Downdraught Stromberg Carburetter to the English production model.
| Identifier | ExFiles\Box 122\1\ scan0183 | |
| Date | 16th May 1935 | |
| To Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Hs{Lord Ernest Hives - Chair}/CTS.{C. Trot Salt - Carburation} X1033 Hs{Lord Ernest Hives - Chair}/GR.{George Ratcliffe}14/KW.16.5.35. 18-G-IV. Downdraught Stromberg Carburetter with Central Water-Heated Floor Manifold. This carburetter was found to be the American model and differs considerably in construction from the present English production. The chief alterations are the separation of the accelerator pump and the economiser or bypass valve. On the present type these can be adjusted independently of each other. The low speed passages also differ in the two carburetters. The present type has an idling air screw, whereas the American has the adjusting screw operating at the throttle edge controlling the supply. This latter of course gives a very sensitive setting for tick over. This American carburetter was very poor for acceleration between 5 & 20 m.p.h. being far too weak either part or full throttle. Above 25 m.p.h., carburation appeared O.K. With tappet clearances set at .015" very good even slow running was obtained at 3 m.p.h. This is the best result yet obtained. With tappet clearances reduced to .010" the engine immediately becomes uneven at the same speed; having a regular hesitation. By increasing the speed to 4 & 5 m.p.h., this hesitation gradually decreases. The car was taken over to Birmingham and the necessary jets obtained to improve carburation between 5 & 20 m.p.h. both at part and full throttle. This was gradually improved without altering the high speed performance by reducing the main metering jet and increasing the bypass jet. The only fault now lies between 10 & 15 m.p.h. at full throttle on a fairly steep gradient in top gear. This fault may not be apparent on the present type carburetter due to detail improvements. Hs{Lord Ernest Hives - Chair}/G.Ratcliffe. | ||