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 power development, detailing experiments with long duration cams, compression ratios, and induction pipe depression.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 113 | |
| Date | 31th March 1927 | |
| contd :- -3- still more power at the higher speeds. Previously - on the standard engine - we have been somewhat limited in raising the compression ratio because of the increased tendency to detonate. This point however will receive further investigation. EXPERIMENT SHEWING THAT HIGH INDUCTION PIPE DEPRESSION REDUCES ADVANTAGE POSSIBLE WITH LONG DURATION CAMS. During the previous series of experiments - see report 20 HP. Power Development 31.3.27 - it was shewn that full advantage could not be obtained from the larger dia. valves unless carburetters giving a low induction pipe depression were used. Similar results were obtained in this case when an experiment was made with the standard carburetter and long duration camshaft. The maximum power gain due to the long duration cams under these conditions was only 6% compared with the 22% gain when working under a low depression. The curves on sheet 3, shew these results. All these tests go to shew that each factor in itself, when used alone, does not assume such importance as when used collectively. Tests also emphasise the importance of low induction manifold depression. TOTAL POWER GAIN RESULTING FROM A COMBIN- ATION OF THE KNOWN BENEFICIAL FACTORS. On sheet 2, is given the power curve resulting from a combination of the following factors :- (1) Increased compression ratio 5.45 to 1. (2) Larger dia. valves 1.400" dia. (3) Two Zenith triple diffuser carbs. contd :- | ||