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).
Summary report on eight-cylinder carburation, detailing the effects of throttle bore diameter and idle systems.
| Identifier | ExFiles\Box 123\1\ scan0046 | |
| Date | 24th April 1940 | |
| Copy 1036 from Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden} Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden}4./JS.{Mr Johnson's Secretary}24.4.40. c: HV. c: Jnr.{Charles L. Jenner} c: Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation} EIGHT CYLINDER CARBURATION. SUMMARY REPORT. The attached report deals with fundamentals unaffected by main metering jet settings and comes under two headings A.{Mr Adams} THE EFFECT OF THROTTLE BORE DIAMETER. Reduction in throttle size on a dual Stromberg carburettor from 36 m/m to 30 m/m results in: 12% gain in economy at 20 M.P.H. 6% " " " " 30 " " 5% " " " " 40 to 60. The price to pay is 3% M.P.H. reduction in top speed. Economy is attributed to a reduction in the overlap of idle and main jet systems, and it is obtained without deterioration in performance. Curves show that even with the present set up Cresta does not compare unfavourably with the Buick for economy when a proper comparison is made. B. IDLE SYSTEMS. Explanation and reason for adoption of the secondary air bleed' type of system. The best idling is obtained by reducing secondary air bleed size to the limit, and bleeding as much air and petrol together as early as possible in the system. DATA SHEET. Chassis used for the tests - 4.B.50. Engine unit - B.80.No.1. Carburettor setting - Main jets .051 Ringed Mechanical by-pass 52 -# Idle jets - 70/- petrol feed 54/- air feed. Sec. air bleed 60 -# | ||