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).
Performance improvement experiments on the Wraith model, focusing on the exhaust system, pistons, and camshaft.
| Identifier | ExFiles\Box 108\2\ scan0216 | |
| Date | 8th February 1939 | |
| 605 To Sy. Sg.{Arthur F. Sidgreaves - MD} c. Hs.{Lord Ernest Hives - Chair} c. RRC. c. Cx.{Major Len W. Cox - Advertising Manager} W/S. c. Sr. W/P. Rm.{William Robotham - Chief Engineer}8/WH.8.2.39. WRAITH PERFORMANCE. In view of Sr's comment on the wraith performance, we have been carrying out some experiments to see what can be done to improve this particular feature of the car. Where we can get something for nothing, it is, of course, standardised immediately on all cars. This applies to the new exhaust system, which improves the top speed of the car by 1 - 2 m.p.h. and which has been instructed for 'D' series. Two other features which do not give us something for nothing are (1) 6½ - 1 C/R pistons. (2) Bentley V camshaft. The increase in C/R makes the engine slightly rougher, the camshaft makes the valve gear slightly noisier and the idling is not so good but still quite fair. To get the best out of these modifications it is essential that they should be used with the new exhaust system previously referred to. The improvement in performance obtained is approx. Ex. System........ 1 - 2 m.p.h. Camshaft and Comp.. 5 - 6 m.p.h. The camshaft is mainly responsible for the increase in top speed, the pistons improve acceleration. Obviously the durability will not be so good with the increased output from the engine. If the modifications are to be fitted in any quantity, they should be applied to Mx{John H Maddocks - Chief Proving Officer}'s car and run on the Continent. The strip of the last Wraith engine was so good, however, that we do not anticipate serious trouble. | ||