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).
Technical report on carburetter performance, air valve function, and throttling characteristics at various engine speeds.
| Identifier | ExFiles\Box 97\2\ scan0211 | |
| Date | 20th June 1941 | |
| -cont'd- - 2 - Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation}5/SW.20.6.41. (a) Hot spot temperature of 35°C (where the main jet takes over from the S.U. automatic starter) (b) Low under bonnet temperature (no radiator shutters), coupled with condition (a). NOTE:- The basic standard worked to in arriving at this setting, was that the driver should not be aware of (a) or (b) on the coldest day. Considering the constant speed curves, we find that throttling back at 4,000 r.p.m., the carburetters run rich. But throttling back at 3,000 r.p.m., the correction is not too bad just off full throttle, followed by a weakening characteristic down the rest of the power range, at that speed. 2,000 and 1,000 r.p.m., show the same symptoms, but weakness is encountered as soon as the throttle is moved away from the full throttle position. The difference between the part throttle corrective action at the higher revs, is due to the fact that the air valve is hard on the ceiling of the carburetter right down the power range at 4,000 r.p.m., and part of the way at 3,000 r.p.m. This in turn is due to the unusual amount of restriction set up by the air silencer system. (The under side of the air valve is at atmospheric pressure). Test No.3. Analysis of the effect of the air silencer and bend, showing how the normal function of the air valve is upset. Test No.3a. Air valve lift plotted against B.H.P., shows (as already stated), the air valve at max. lift over nearly the complete power range at 4,000 r.p.m., and nearly half the power range at 3,000 r.p.m. CONCLUSION. The depression in the main gallery is increased by 33.1/3% by using the standard (continued) | ||