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).
Experiment report on how high induction pipe depression reduces the performance advantage gained from long duration cams.
| Identifier | ExFiles\Box 5a\5\ 05-page051 | |
| Date | 31th March 1927 | |
| contd :- -3- 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 carburettors giving a low induction pipe depression were used. Similar results were obtained in this case when an experiment was made with the std. carb. and long duration camshaft. The max. 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 much importance as when used collectively. Tests also emphasise the importance of low induction manifold depression. TOTAL POWER GAIN RESULTING FROM A COMBINATION 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 carburettors. (4) Long duration inlet and exhaust cams. The curve for the std. engine with its 4.75 to 1 compression ratio is given for comparison. All these tests were taken with free exhaust - short pipes 7" long were used for each port. contd :- | ||