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 improvements of a 20 HP car after modifications to its compression ratio, exhaust, and carburation.
| Identifier | ExFiles\Box 5a\5\ 05-page006 | |
| Date | 1st December 1926 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to BJ. Wor.{Arthur Wormald - General Works Manager} c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} K5721 Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LGS.12.26. 20 HP. PERFORMANCE. X3405 (crossed out) X1725 We have been conducting a number of tests on the 20 HP. to ascertain what improvement we have effected in performance on the road by the various modifications to the compression ratio, exhaust system and carburation which have recently been made. As will be observed from the attached curves, when equipped with all the known improvements, the 20 HP. is a very lively car. Fitted with a standard 11/50 axle and normal Windover touring body, hood and side curtains up, we have attained 70 m.p.h. under slightly favourable road conditions. This, however, is rather unpleasantly near the critical crankshaft speed which can easily be reached on the lower gears. We are rather surprised at the improvement effected by the cutout at low speeds - the new manifold has undoubtedly made the cutout an effective item. The behaviour of the single triple diffuser Zenith carburetter exactly as removed from the Lorraine is remarkably good. It cannot be opened up suddenly below 20 m.p.h. but gives good acceleration even at this speed if humoured. The increase in liveliness at high speeds is distinctly noticeable. We are carrying out a test with two of these carburetters. We are also considering some modification to the engine mounting to try and minimise the reaction of the vigorous power impulses. Attached are some figures of performance for the 40/50 HP., from which it will be seen that the modified 20 HP. closely approaches the performance of the standard Phantom. Hs{Lord Ernest Hives - Chair}/W.A. Robotham. | ||