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).
Spectre engine ignition tests to determine the minimum advance curve for maximum power.
| Identifier | ExFiles\Box 4\1\ 01-page207 | |
| Date | 7th January 1935 | |
| X300 To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Swd1. c. to H.r. c. to Hy.{Tom Haldenby - Plant Engineer} c. to R.H.C. & W.A.S. Hs{Lord Ernest Hives - Chair}/Swd1.19/KW.7.1.35. SpectreCodename for Phantom III Ignition. Tests have been taken in order to obtain a curve of the minimum advance necessary to give the maximum power at each speed, the results being shewn on S.P.8. These tests have been carried out with the test bed exhaust system, Lodge 398 Inlet Spark Plugs and K.L.G. 808 Exhaust Spark Plugs, the compression ratio being 8:1. Both ignition governors being synchronised, the ideal setting is 15° before T.D.C. at 500 r.p.m. up to 35° before T.D.C. at 4000 r.p.m. Assuming from the curve that 2° - 3° more advance is necessary when running up to speeds of 4500 - 5000 r.p.m., the existing governor gives the correct total advance of 32°. The present springs (E.57915) allow the governor to reach the fully advanced position at 2000 r.p.m. which if set according to the ideal figures of 15° before T.D.C. at 500 r.p.m. is 12° too far advanced at 2000 r.p.m. and comes outside of the 2% power drop curve. By fitting Hs.{Lord Ernest Hives - Chair}1676 governor springs, the curve, when timed at 15° before T.D.C. with the hand control in the full advanced position, follows very closely to the ideal advance curve and well within the 2% power drop lines. As there is no audible detonation at the low speeds on this engine we are able to adhere to the ideal curve throughout. When assembling the governor, the springs (Hs.{Lord Ernest Hives - Chair}1676) should have no initial tension on the governor weights, and the weights should have up to .010 movement before coming on to the springs. | ||