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).
Indicator work and performance tests carried out on a Hispano engine.
| Identifier | ExFiles\Box 180\M4\M4.1\ img040 | |
| Date | 12th July 1923 | |
| R.R. 493A (40 H) (SL 42 12-7-23). J.H. D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expt. No. 4214 4580 REF: Hs{Lord Ernest Hives - Chair}/Rn{Mr Robinson}/LG12.3.24. HISPANO INDICATOR WORK. We have carried out tests on the Hispano engine with the original R.A.E. Electrical Indicator. The mechanical efficiency curve of this engine, as we have plotted it from the indicator diagrams, appears to be rather unconventional. We have shewn the extent of variations that we encountered on the graph. The mechanical efficiency at high speeds is undoubtedly rather better than either of the 2 R-R engines. The volumetric efficiency of this engine, and consequently the compression pressure, peaks sharply at 1500 r.p.m. with the natural result of a high I.M.E.P. at this speed. We believe the 3-cylinder induction system to be responsible for the high efficiency of this speed, rather than the valve timing, there being a possibility of pulsations being set up. We intend to investigate this point. The compression pressure at 1500 r.p.m. is 105 lbs/sq. in. which corresponds to a compression ratio of about 4.8 to 1. The fact that this engine does not experience its highest M.E.P. at low [handwritten above 'high'] speeds, and also has two plugs on opposite sides of the combustion chamber, materially affects its detonation propensities. With two plugs firing, the max. explosion pressure we registered at any time was 525 lbs. per sq.in. When we removed one plug and inserted the indicator valve in its place, the max. explosion pressure registered exceeded 700 lbs. per sq. in. contd:- | ||