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).
Comparative power and road performance report on a 20 HP engine with an increased bore.
| Identifier | ExFiles\Box 125\2\ scan0035 | |
| Date | 27th April 1929 | |
| To R.{Sir Henry Royce} from HS{Lord Ernest Hives - Chair}/AJL. c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} c. to BY.{R.W. Bailey - Chief Engineer} PN.{Mr Northey} X4012 HS{Lord Ernest Hives - Chair}/AJL1/LG27.4.29. ------------------ X.4012 X.5771 X.1725 X.438 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 carb. 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 S.S. Power at Road Wheels. The increase in power by the larger engine over standard is remarkable, varying from nearly 50% at 2500 r.p.m. to 30% at 500 r.p.m. During the test, trouble was experienced at high speeds due to pre-ignitions when using K.L.G. K1. 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 contd:- | ||