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).
Tests carried out on a higher compression cylinder head, comparing twin choke and single expanding carburetors.
| Identifier | ExFiles\Box 179\2\ img025 | |
| Date | 9th December 1931 | |
| R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/sn.{Mr Sanderson} C. to Sg.{Arthur F. Sidgreaves - MD} Rr. C. to S. Ds. ORIGINAL TM/sn.{Mr Sanderson}7/MA.9.12.31. x7050 x7080 HIGHER COMPRESSION HEAD 40/50. No. f2456 We have carried out tests on a Cyl Head piece a drawing of which we attach. The two curves MP.46 and MP.44 show 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} Carburetter. 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 Dia. expanding. 8 20 26.5 These results rather show 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. shows 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}/sn.{Mr Sanderson} Attached Rn.{Mr Robinson} P.46 Rn.{Mr Robinson} P.44 X. 82455 attached to E's. and R's. copy only. | ||