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).
Comparison table of magneto performance data, including spark timing and operating speeds.
| Identifier | ExFiles\Box 4\5\ 05-page228 | |
| Date | 19th July 1922 guessed | |
| -2- Magneto. | Degrees of make. | Makers make advd. | Makers break advd. | Our break advanced. | Our break retarded. | Lowest speeds for 5.5 mm. Adv. Cent. Retd. | REMARKS. Eisemann | 150.5 | +53.5 | 97° | 97° | 131° | 155 | 177 | 238 | Advanced position as maker but more advanced than to allow proper high speed sparking by 7° U.S.A. Bosch. DUZ6 | 156.5 | -58 | 98.5 | 98.5 | 132.5 | 102 | 124 | 180 | Advanced posn. the same as makers. Retard posn 1° earlier than makers. CHAIN DRIVE ADOPTED. U.S.A. Bosch ZR6 | 156.5 | -57.5 | 99 | 99 | 133 | 56 | 105 | 150 | Advd. posn. same as makers. Our retard 2° earlier than makers. Watford ELC6 | 158.5 | -74.5 | 84 | 84 | 118 | Irregular sparking at all speeds. | 245 | | Advd. and retd. position same as makers. Range limited by movable sleeves. Watford ELC6 | 159.5 | -81.5 | 78 | 106 | 140 | 67 | 68 | 69 | Retd. posn. same as makers. Our adv. 28° later than maker. | ||