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).
The comparative power and road performance of a 20 HP engine with an increased bore.
| Identifier | ExFiles\Box 5a\5\ 05-page093 | |
| Date | 27th April 1929 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/AJL. c. to Sg.{Arthur F. Sidgreaves - MD} Mor. c. to E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} c. to BY.x PN.{Mr Northey} X5771 Hs{Lord Ernest Hives - Chair}/AJL1/LG27.4.29. X4012 - X5771 ✓ Y1725 X488- 20 HP. COMPARATIVE POWER AND ROAD PERFORMANCE. First tests on 20 HP. engine with additional .200" on bore. We give herewith results obtained on the first tests on a 20 HP. engine - bore 3.200", turbulent head, 5.25/1 comp: ratio and 14% larger carburetter chokes and air valve ports. For comparative purposes we have shewn results obtained from 20 HP. (std.) 20 HP. with turbulent head (5.1/1) Chrysler and super sports. Power at road wheels. The increase in power given by the larger engine over standard is remarkable, varying from nearly 50% at 2500 r.p.m. to 30% at 800 r.p.m. During the test, trouble was experienced at high speeds due to pre ignitions when using KLG. KL. plugs, this was overcome by employing Lodge A.40. plugs but at low speeds these emphasised carburation trouble in the form of 'loading up'. As a compromise we are using Champion R.11 plugs for road work. The conditions on the dynamometer were rather bad for low speed full throttle conditions viz: air temperature low, no bonnet, water heated bend, the induction pipe was at a very low temperature throughout the test. The same trouble was experienced in a slightly less degree when testing the turbulent head 5.1/1 comp: ratio engine. The increase in power over the Chrysler is very pronounced, in spite of the fact that the Chrysler eng. is larger. contd :- | ||