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).
Analysis of engine power output and airflow tests comparing SS and standard F.2.B. cylinder heads and valves.
| Identifier | WestWitteringFiles\S\September1928-October1928\ Scan189 | |
| Date | 26th October 1928 guessed | |
| contd :- -3- becoming troubled with detonations. We will test ratios up to 5 to 1. Analysing the results of the tests and referring to the curves shewing the power output of the SS.{S. Smith} with low depression carb. compared with the std. F.2.B. engine we should say that of the observed power gain 8.1% is due to the carb. 2.8% due to the higher comp: ratio and 7.5% due to the larger valves and passages. See curve V.468. We anticipated rather more gain from the latter and expected the power peak to occur at an appreciably higher speed. We therefore made a static test and comparison of the air flow past the valves both on the SS.{S. Smith} and F.2.B. engine. This was accomplished by means of a P. engine supercharger which blew air into the valve port, the measurement of flow being taken by means of an air venturi meter. A vernier adjustment was provided by which the valve could be lifted to any required height. A sketch of the apparatus employed is appended. Various pressure heads were employed and the air g flow recorded for various valve lifts on both cyl. heads. A set of curves are supplied shewing the air discharge past the valves - both the SS.{S. Smith} and F.2.B. - in lbs/min. for various pressure differences and for various lifts of the valve. From these curves are drawn a second set shewing how the air flow varies with the valve lift, the pressure drop across the valve remaining constant at 2.8 lbs/sq.in. This represents approx. the condition at 2500 r.p.m. The point of interest of these curves is firstly, the greater air flow resulting with the SS.{S. Smith} valves and ports for a particular lift contd :- | ||