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 specifications, including lead and retard angles for a magneto-equipped engine at various RPMs.
| Identifier | ExFiles\Box 37\1\ scan 222 | |
| Date | 15th February 1921 | |
| R.R. 554. (100 T) R.W. 728. 10.12.20. C. 2927 X.3949 To Hs.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} c. to CJ. c. to EFC. R9/G15.2.21. X.699 - RE IGNITION TIMING. X.928. X.3949. With the magneto, we find the little engine here which runs at 750 revs. with normal mixture, requires practically no lead, for the best power. I should be glad if you would let me know what your estimate is of the lead as needed for 3,000 revs. and how much you think it should be retarded for starting. Supposing we said on the crankshaft 20º in each way, this should be a total change of angle of 40º, 20º at about 500 revs. increasing 40º at 3,000 revs. These are something like the particulars we require, to arrange the ignition governor and hand control, and refer to engines of the compression and build of the Marmon and Buick type. R.{Sir Henry Royce} | ||