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).
Surprisingly low performance improvements of a 20 HP engine fitted with a new Turbulent Head.
| Identifier | ExFiles\Box 19\7\ Scan140 | |
| Date | 22th April 1929 | |
| SG.{Arthur F. Sidgreaves - MD} from R.{Sir Henry Royce} c. to Wor.{Arthur Wormald - General Works Manager} Hs.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} c. to E.{Mr Elliott - Chief Engineer} PN.{Mr Northey} C. EP.{G. Eric Platford - Chief Quality Engineer} 4790 RL/M22. 4. 29. 20 HP. TURBULENT HEAD ETC. X. 5050 X. 790 X. 5770 I am somewhat surprised that no definite improve-ment was found between London trials car and G.4. One can only think there is some quite remarkable advantage in both power and smoothness between a well run in chassis (really engine) and a somewhat raw one, (i.e. the production twenty's do better HP. after being in use some time). We do not expect much from the head alone. It was only thought to have the advantage of being less liable to detonations, and so possibly enable an increase in compression ratio. We have not I believe increased the compression, but rather left the engine safer from detonations. We have with the new head such an improved inlet and exhaust system that unless we have done something wrongly we expected the engine to fill up better, have better distribution, and that more HP. would be obtained. Also we should get two other improvements - i.e. good cold distribution (starting away quickly cold) and also no explosions in the exhaust. Moreover I have before me memo. Hs{Lord Ernest Hives - Chair}/ACL/28.3.29. a report giving - at 2500 revs. an increase of over 11 HP. in 48 - really 23. It cannot be possible that this has no effect, and it is difficult to believe it can be masked by the difference of a free running engine. Moreover I cannot believe that Mr. Hives and Mr. Platford would leave Derby with a car that gave no more HP. on the test bed or dynamometer than the present standard 20's. Perhaps in addition to the free running in, the body was different, either heavier or greater windage, or the engine revs. were so high that the valves were jumping. Will E.{Mr Elliott - Chief Engineer} telephone this message to Hs.{Lord Ernest Hives - Chair} and wire me some results. We cannot also understand a rougher engine unless mechanically tight, or more power, because the compression ratio is the same. R.{Sir Henry Royce} | ||