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).
Test results on a higher compression 40/50 cylinder head, comparing twin choke and single expanding carburetters.
| Identifier | ExFiles\Box 14\3\ Scan073 | |
| Date | 8th December 1931 | |
| X7050 X7080 T. From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to SG.{Arthur F. Sidgreaves - MD} Sor. c. to S. Da.{Bernard Day - Chassis Design} c. to Sy. HIGHER COMPRESSION HEAD 40/50. We have carried out tests on a Cyl head piece No. E 82455, a drawing of which we attach. The two curves WP.46 and WP.44 shew the results of this head when using the twin choke carburetter and a big single expanding carburetter. The figures are rather surprising as we gain considerably more than we should expect from the air cycle efficiency curve. Furthermore the single carburetter gains considerably more from the increase in compression ratio than the twin at all speeds as will be seen from the following table. Gain increasing from 4.6 to 5.2 C/R.{Sir Henry Royce} Carburetters. B.M.E.P. 1500 RPM. B.H.P. 3000 RPM. B.H.P. 3500 RPM. R.R. Twin choke 5.5 15 18 2.5" Throttle Dio expanding. 8 20 26.5 These results rather shew that it is impossible to correct for compression ratio by calculation unless the exact factor for the camshaft and induction system are known. The standard Carb. shews considerably less gain than the twin for any given increase in compression ratio. We think it likely that the 5.22 C/R head will be quite a feasible proposition from the point of view of detonation with a single carburetter or non ramming double carburetters. We shall take the opportunity of confirming these results as soon as possible. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} attached Rm.{William Robotham - Chief Engineer} P.46 Rm.{William Robotham - Chief Engineer} P.44 E.{Mr Elliott - Chief Engineer} 82455 attached to E's. and R's. copy only. | ||