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 timing, detonation, and self-ignition characteristics of a turbulent type cylinder head.
| Identifier | ExFiles\Box 17\6\ Scan008 | |
| Date | 10th December 1926 guessed | |
| contd :- -4- timing as late as 15° before top centre and only reduce our B.M.E.P. by 1.3 lbs/sq.in. With single ignition and the same late timing we should lose 4.5 lbs/sq.in. Single ignition with this engine approximates in effect closely to the synchronised with the standard Phantom, therefore with this engine we could expect to use much later timing which we hope in practice would go a long way towards the reduction of detonation. The advance required over the whole full throttle range shown on curve 2, is seen to be slightly less than required by the previous alum: head and considerably less for the standard Phantom, particularly so at low speeds. This we take it is evidence that greater turbulence is maintained due to the greater area available for expelling the charge from between the piston and the cylinder head into the combustion space. SELF IGNITION AFTER SWITCHING OFF. In a previous report we stated that with the original ignition turbulent type head self ignition was evident after switching off from full throttle. This exists with the latest head tested but we consider the trouble is considerably less severe with either of these turbulent type heads than the std. The test on the std. engine was to run with 2/3rds. load at 2000 r.p.m. for two minutes and then throttle down to 500 r.p.m. and see what time had to elapse at this speed before the engine could be switched off and give no self ignition. The standard engine required 28 secs. but contd :- | ||