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 increases achieved through modifications to valves and carburetters.
| Identifier | ExFiles\Box 19\7\ Scan101 | |
| Date | 1st April 1927 guessed | |
| contd :- -4- We have observed that the power increase is just what would be expected from the reduction in depression. The maximum power - at 2750 r.p.m. - has been increased from 58 to 63 B.HP. or nearly 9%. At 2000 r.p.m. the power increase with two carburetters is just over 15%. INCREASE OF POWER WITH LARGER VALVES. On Print No.2. curves are given shewing the effect of the larger valves when tested with the two Zenith carbs. Gas velocity curves are also given separately. The maximum power occurring at approx. 2750 r.p.m. in each case has been increased from 63 to 70 B.H.P. or a gain of 11%. The effect of the lower gas velocity is better shewn by the B.M.E.P. curves which illustrates apart from the increase in M.E.P., how it is maintained at a higher speed. The B.M.E.P. reaches a maximum of 119.7 lbs/sq.in. at 1850 r.p.m. but it must be remembered that this is with free exhaust and 5.45 to 1 comp: ratio if comparison is made with the previous curves submitted for the Lorraine. We therefore see from these tests that a considerable increase in power is affected by a combination of low depression carbs. and larger valves. POWER INCREASE WITH LARGE VALVES AND LOW DEPRESSION. Print No.3. shews the total gain in power given by the larger valves and two low depression carbs. compared with that obtained from the std. valves and carb. The max: increase is 12 HP. at 2750 r.p.m. which represents 20%. contd :- | ||