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 settings for the high compression 20/25 HP car.
| Identifier | ExFiles\Box 51\5\ Scan254 | |
| Date | 12th May 1930 | |
| x5681 To EP. {G. Eric Platford - Chief Quality Engineer} From Hs {Lord Ernest Hives - Chair} /AJL. c. to MX. {John H Maddocks - Chief Proving Officer} c. to BY. {R.W. Bailey - Chief Engineer} Hs {Lord Ernest Hives - Chair} /AJL.2/WJ.12.5.30. x5270 x5331 x5681 HIGH COMPRESSION 20/25 HP. CAR. IGNITION SETTING. We have recommended and instructed a battery ignition setting of 13° B.T.D.C. when fully advanced on the hand control. The higher compression engine needs considerably less ignition advance for maximum power than the 4.75 compression engine. In order to ensure reasonable freedom from detonation the ignition timing was fixed to give a 2% drop from maximum power. We know that it will be possible to detect an increase in power both on the bench test and on the dynamometer by advancing the ignition earlier than 13° B.T.D.C., but this small increase of 2% is not detectable on the road whereas the additional margin of freedom from detonations which it gives is well worth having. The battery advanced position (13° B.T.D.C.) should be used as a flywheel indication in preference to the retarded point in order that any slack in the controls will cause a loss on the retard side rather than on the full advanced setting. The correct ignition leverage will produce an advance setting of 13° B.T.D.C. and retain the old 10° P.T.D.C. retard position. Hs {Lord Ernest Hives - Chair} /AJL. | ||