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).
Power development test on a 20 HP engine using stronger valve springs and a long duration camshaft.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 131 | |
| Date | 26th May 1927 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/ACL. c. to BJ. Wor.{Arthur Wormald - General Works Manager}✓ c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to BY.{R.W. Bailey - Chief Engineer}✓ Hs{Lord Ernest Hives - Chair}/ACL1/LG26.5.27. 20 HP. POWER DEVELOPMENT - STRONGER VALVE SPRINGS WITH LONG DURATION CAMSHAFT. X8090 X.5771 We have now made a test with the long duration camshaft and some stronger valve springs in order to prevent the valve bounce at 3000 r.p.m. previously experienced. The peak of the power curve now occurs at approx. 3300 r.p.m. giving 92.5 B.HP. The B.M.E.P. at this speed is as high as 115 lbs/sq.in. This gives an increase of max. HP. over the standard engine of 71% and of this only approx. 10% is due to the higher compression ratio. These experiments prove that the 20 HP. is capable of very high power output and an efficiency of .5 pts/HP/Hr. is obtainable. The limiting factor on the std. engine is the high depression necessary to secure correct functioning of the carburetter. We have previously made several attempts to enlarge the std. carb. and obtain a low depression, but as in the case of the Phantom, have always found we could not obtain satisfactory operation if we appreciably departed from the present dimensions. For an experiment we will test the Zenith carbs. we have been using for these tests, on the road to see how its low speed and acceleration performance compares contd :- | ||