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).
Spring-loaded piston fitting designed to improve engine performance at low speeds.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan69 | |
| Date | 13th August 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. Expl. No. REF Hs{Lord Ernest Hives - Chair}/AJL/LG13.8.25. C to choke the mixture drawn into the induction pipe at low engine speeds (closed throttle), but does not take any effect at full throttle. The spring loaded piston is arranged to commence restricting the carburetted air when the induction pipe depression exceeds 6" of mercury. At a lower depression than this the piston is not moved and the air has a free passage into the induction pipe. The greater the induction pipe depression the more is the gas restricted. We find that the fitting certainly improves the faulty running at low speeds, but does not entirely eliminate it. The effect is to spread the unevenness out over a slightly longer period than when the standard suction elbow is employed, also to lower the depression in the Autovac - the combination of these two effects reduces the carburetting action of the Autovac. The curves attached show the effect of this suction elbow on the efficiency of the Autovac. It will be noticed that there is no difference at all when the engine is running under full throttle conditions. The decrease of the Autovac depression at low speeds has the effect of increasing the time taken to fill the Autovac float chamber, this increase is really very slight and we do not imagine that the difference will increase the possibility of the Autovac running dry under road conditions. Hs{Lord Ernest Hives - Chair}/AJL. | ||