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).
Ignition timing adjustments for high compression 20/25 HP cars.
| Identifier | ExFiles\Box 51\5\ Scan252 | |
| Date | 5th May 1930 | |
| X5681 To Mx. {John H Maddocks - Chief Proving Officer} From Hs {Lord Ernest Hives - Chair} /AJL. c. to Ey. HS {Lord Ernest Hives - Chair} /AJL.1/MJ.5.5.30. X5681 X5770 X5771 X5680 IGNITION TIMING ON HIGH COMPRESSION 20/25 HP. CARS. With reference to Mx. {John H Maddocks - Chief Proving Officer} 7/T.3.5.30., we have asked the D.O. for the necessary ignition control alteration on all high compression cars. With regard to the last two paragraphs:- We are aware of the detonation which occurs when running on magneto ignition at low speeds fully advanced. Owing to the magneto ignition not having an automatic advance this is unavoidable. We already lose power at high engine speeds when using the timing of 5° P.T.D.C.; any later setting causes a large loss of power at high speeds. The old low compression engine timings as compared with the recommended high compression timings are as follows:- Low Comp. High Comp. Battery Ignition Full Retard Setting. 10° PTDC. 10° PTDC. " " Advance " (on quadrant) 30° BTDC. 13° BTDC. " " " (quadrant and Automatic) 60° BTDC. 43° BTDC. Magneto " Retard Setting TDC. 5° PTDC. " " Advance " 36° BTDC. 31° BTDC. When it is realised that the high compression engine is naturally more prone to detonations and more sensitive to ignition control at high speeds, the recommended timings do | ||