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 settings for cold weather, detailed carburetter specifications, and an investigation into the engine running on after being switched off.
| Identifier | ExFiles\Box 147\5\ scan0186 | |
| Date | 4th September 1941 | |
| -cont'd- - 3 - Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden}10/SW.4.9.41. The economy setting on B.V. is virtually a standard B.ll setting - and it has a Startex and fixed shutters. It cannot be denied that the odds are against it if the winter is cold. The amount by which the carburetters have to be strengthened up in cold weather to reproduce B.ll performance, may be charged to the account of underbonnet temp- erature. It is anticipated that they will have to be brought back to approximately the original B.V. setting. Underbonnet temperature would appear to have a big debt to pay. Carburetter Specification. Single downdraught Stromberg on a 2 port pipe (RE.155) DC.42 type main body. DBV.30 type throttle body (30 m/m). .042 main jet. .021 by-pass (mechanical). Idle tube - No.68 petrol feed, No.75 air feed. Idle hole in throttle body No.54. Progression hole in throttle body No.53. Main discharge tube as fitted to DBV.36 type carb. .080 seating for float chamber needle. Engine Unit. B.40 No.1 Axle Ratio 10 x 43. Rear tyres Dunlop 5.25 x 16 (Worn) @ 35 lb/in2. Running on after switching off. We ran for 2 miles at 30 MPH full throttle in direct gear and then switched off. The engine ran on for 45 seconds. After a similar run at part throttle, the engine ran on for 5 seconds. The engine is undoubtedly getting hotter at full throttle, but some part of the difference in running on time is probably due to the fact that the walls of the induction pipe are wet after full throttle and dry after part throttle running. With this clue in mind, we had considered a scheme for cutting out the idle system when the engine is switched off. This is now thought to be insufficient, and hardly worth the complication involved. -continued- | ||