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).
Modifications to the Phantom III Duplex Stromberg Downdraught Induction System and subsequent performance improvements.
| Identifier | ExFiles\Box 20\9\ Scan116 | |
| Date | 11th February 1936 | |
| X1033 To E.{Mr Elliott - Chief Engineer} c. to Wcr. c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}16/KW.11.2.36. Phantom III. Duplex Stromberg Downdraught Induction System. Further to our report Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}4/MA.7.1.36, we have since confirmed our previous result in that there is 10-12 H.P. loss with the induction system LeC.4748 against the power obtained with the mock-up system. Following this report, the hot spot LeC.4863 was modified to LeC.4919 whereby the passages from the carburetter to the manifolds were made more gradual, less liable to create restrictive turbulence in the hot spot box. In conjunction with this modification LeC.4919, a modification was also carried out on the branch manifolds to LeC.4920, giving an improved radius from the main pipe into the actual branches. The combined result of these two modifications has brought the powerup to that obtained with the mock-up scheme and the distribution with the two systems is identical both at high and low speeds. Confirming the pick up in power, the induction pipe depression is reduced from 3.6" to 3.0" Hg. at 3750 R.P.M., also obtaining the latter figure with the mock-up system. These comparisons have been taken on No.19 unit which is 6 - 8 B.H.P. down for power compared with No.9 unit with the same induction system. The results on No.9 unit were as quoted in the report Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}4/MA.7.1.36, and we are not quoting the actual power on No.11 unit until the conditions of both are brought more into line with each other. (a) No.11 is running with 4° - 6° earlier valve timing. (b) No.11 has Mx.{John H Maddocks - Chief Proving Officer} type pistons (E.87810), the skirts of which are up to bore size, whereas No.9 had E.87347 pistons, the skirts of which are .002" under bore size. We are however satisfied that the modifications LeC.4919/20 have brought the power up to that obtained on the mock-up system throughout the speed range, and recommend that this system is included in the specification for production immediately. | ||