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 indicator cards, discussing performance, pressure, timing, and factors affecting them.
| Identifier | WestWitteringFiles\L\July1924-September1924\ Scan42 | |
| Date | 12th July 1923 | |
| R.R. 403A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} -2- EXPERIMENTAL REPORT. Expl. No. REF: He/Rm{William Robotham - Chief Engineer}/LC5.9.24. INDICATOR CARDS. It will be observed from the indicator cards that the cylinder fills up very well, the compression pressure being about 85 lbs/sq.in. The conventional compression ratio of the engine being 3.45 - 1, this corresponds to a volumetric efficiency of over 100% due to the supercharge. We are of the opinion that this is a flattering figure as the charge is bound to have undergone a considerable amount of pre-heating before it reaches the cylinder. The best ignition point is 14º B.T.D.C. and the charge ignites very slowly, the peak pressure being delayed until 30º A.T.D.C. The peak pressure is very low, the resultant I.M.P. being 54½ lbs/sq.in. This figure agrees very well with that of 53¾ lbs/sq.in. obtained by motoring and brake tests. There are two external factors which may influence this :- (a) Position of the plug. At present we have only been able to use the plug in the transfer port. (b) Carburation. This does not seem to be very satisfactory - we are trying another carburette In addition to these we have the fact that the scavenging port opens when the pressure in the cylinder is 80 lbs/sqin. The scavenging pressure for the test was 3 lbs./sq.in., so that for at least 15% of the stroke, exhaust gas was being blown into the reservoir. When, therefore, scavenging finally commences, there appears to contd :- | ||