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 control comparison for a high compression 25 HP car engine versus the standard model.
| Identifier | WestWitteringFiles\U\January1930-April1930\ Scan084 | |
| Date | 2nd August 1930 | |
| E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/AJL. c. to By.{R.W. Bailey - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} HS{Lord Ernest Hives - Chair}/AJL. 2/J.G. 2.8.30. x5770 x5771. x5680. IGNITION CONTROL FOR HIGH COMPRESSION 25 HP. CAR. It is found that the 5.25:1 compression ratio 25 HP. car does not require so much ignition advance as the standard 25 HP. car engine. Maximum power and reasonable freedom from detonations are given by a battery ignition timing 17° later than on the standard engine. The standard timings and the timing required by the new engine on battery ignition are as follows:- BATTERY IGNITION. | | FLYWHEEL DEGREES. | | | | Standard 25 HP. engine. | R.{Sir Henry Royce} 5.25:1 25 HP Engine. | | Full retard timing on quadrant. | 10° P.T.D.C. | 10° P.T.D.C. | | Full advance timing on quadrant. | 30° B.T.D.C. | 13° B.T.D.C. | | Full advance automatic and quadrant. | 60° B.T.D.C. | 43° B.T.D.C. | | Range of advance by hand on quadrant. | 40° | 23° | | Range of advance by automatic governor. | 30° | 30° | The range of advance by the automatic ignition governor should remain as it is and the range of advance obtained by hand on the control quadrant should be reduced from 40° to 23°. This applies to battery ignition only. | ||