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 comparing Mean Effective Pressure vs. engine R.P.M. for a spark plug in the exhaust position versus the side position.
| Identifier | ExFiles\Box 134\1\ scan0121 | |
| Date | 10th January 1939 guessed | |
| CURVE d.{John DeLooze - Company Secretary} COMPARISON OF PLUG IN EXHAUST POSITION AGAINST SIDE POSITION. NON DETONATING POWER REDLINE. RAMP HEAD & STD. PISTON. 6.6 : 1 RATIO ① PLUG IN EXH. POSITION ② " " SIDE " " M.E.P. 130 120 110 100 0 1000 2000 3000 4000 R.P.M. | ||