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).
Graph plotting ignition advance and BMEP against RPM for a 4¼ Litre Bentley engine under various conditions.
| Identifier | ExFiles\Box 90a\1\ Scan006 | |
| Date | 21th July 1938 | |
| B3 UNIT 4¼ LITRE BENTLEY POWER DEVELOPMENT S3 IGNITION-ADVANCE WITH TURBULENCE ① COMP RATIO 9:1 Ex 2594A 2 - 1 7/8 S.U. CARBS. ON 1 3/4 PIPE. F.B. DRS CAMSHAFT (STD) ESSO ETHYL PETROL MIN ADV FOR MAX POWER IN PORTS + .625 IN VALVE 1.700 1.600 Ex " 1.350 1.400 ② POWER LOSS AND IGN ADV TO REDUCE DETONATION TO REASONABLE DEGREE OTHERWISE AS ① ③ COMP RATIO 8.5:1 Ex 20943 PURE BENZOL MIN ADV FOR MAX POWER OTHERWISE AS ① IN PORTS + .625 IN VALVE 1.600 1.700 Ex " 1.400 1.350 CRANKSHAFT DEGREES B.T.D. B.M.E.P. R.P.M. | ||