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 requirements for a small engine, including lead and retard angles.
| Identifier | WestWitteringFiles\F\February1921\ Scan104 | |
| Date | 1st February 1921 | |
| To HS.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} Copy to EFC. ORIGINAL. (5) R9/G15/2/21. X699. RE IGNITION TIMING. X 928 W.W LIGHTING SET X.3149. 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 20° in each way, this should be a total change of angle of 40°, 20° at about 500 revs. increasing 40° 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} V.{VIENNA} | ||