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).
Engine detonation and pre-ignition, comparing the performance of Buick and Standard Bentley pistons.
| Identifier | ExFiles\Box 134\1\ scan0065 | |
| Date | 21th December 1937 | |
| -6- DETONATION. Fig.V. shows a power comparison with the detonation intensity kept constant. It will be seen that the Buick pistons are only slightly better than the standard Bentley with a difference of one ratio, whilst the spark has got to be retarded right up to 3000 r.p.m. when severe pre-ignition sets in. At the same compression ratio, the Buick piston job is appreciably below standard. With regard to the pre-ignition this was put down to excessively hot exhaust valves as it was not affected by either the type of plug used or the water jacket temperature. This phenomenon was so pronounced on one occasion that switching off the engine made only 3 mep. difference in the load pulled. Richening up the mixture made most difference, as is only to be expected. All these tests were run at an engine speed of 3000 rpm. FIG. V — BUICK TYPE PISTONS — COMPARISON OF NON - DETONATING POWER. BUICK TYPE PISTONS (C.R. = 7.42) STANDARD BENTLEY (C.R. = 6.4) BUICK TYPE PISTONS (C.R. = 6.42) — B.M.E.P. — — R.P.M. — — IGNITION ADVANCE — O CIRCLE INDICATES WHERE DETONATION RUNS OUT. continued | ||