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).
Test report on engine spark timing at different speeds, with a table of ignition points versus RPM and comparison to a Packard car.
| Identifier | ExFiles\Box 37\1\ scan 219 | |
| Date | 25th June 1920 | |
| Contd. -3- Hs{Lord Ernest Hives - Chair}7/LG25.6.20. long as they have sufficiently long contact to avoid the spark jumping. We have taken a test with the automatic advance on the engine to see at what point the spark occurs at different speeds. To do this we ran the engine on six cylinders. On the distributor for the other side we fitted a special ring which was marked off in degrees. We could tell on this ring the point at which the spark occurred. Below are the results:- R.P.M. Ignition Point. Stationary. 8º B.T.D.C. 100 8º 300 10º 500 12º 700 14º 900 17º 1100 19º 1300 20º 1500 22º 1700 24º 1900 27º 2100 28º choc-a-block. The standard timing of the battery ignition on the Packard car is such that with the Control Lever fully retarded the spark takes place 21o after T.D.C. if the ignition Contd. | ||