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).
Technical memorandum discussing performance improvements of a single-cylinder car unit, comparing Kestrel and Bentley components.
| Identifier | ExFiles\Box 133\2\ scan0047 | |
| Date | 4th July 1934 | |
| 4706 To Lr.{Mr Ellor} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}11/KW.4.7.34. CAR SINGLE CYLINDER UNIT. During the discussion on single cylinder units the other day we remarked that we believed there was a latent improvement in M.E.P. obtainable on the naturally aspirated Bentley Ramp Head, if only we could put our finger on the spot. The reason we said this was as follows. From the attached curves, which are drawn from figures we got from the single cylinder testers, the Kestrel ramp gives 15 more I.M.E.P. than the Bentley for the same C/R with (1) 20% less valve area per litre (2) The same exposed area of combustion chamber per litre (.3 sq/in/cu.ins.) The Kestrel I.M.E.P. is obtained at 33% lower R.P.M. than the Bentley or 19% lower piston speed so that given the same volumetric efficiency at max. I.M.E.P. we should expect the Bentley I.M.E.P. not only to equal the Kestrel but to be slightly the better of the two owing to the indicated thermal efficiency improving with speed. Therefore we believe that - (a) We are either not reproducing the improvement in volumetric efficiency expected from our blowing tests (b) We are getting incomplete combustion (c) The exhaust valve is preventing the improved volumetric efficiency of the inlet valve being converted into useful I.M.E.P. The increase in detonation inclines us to believe that (a) may not be the trouble. | ||