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).
Report discussing engine performance, including spark plug reach, valve overlap, engine breathing, and exhaust valve temperature.
Identifier | ExFiles\Box 134\2\ scan0165 | |
Date | 16th October 1937 | |
-3- and power and detonation qualities decrease. The reach of the plug was also stated to be a critical factor. If this were too long the plug would become overheated, and if too short, and recessed in the head, then the fresh charge would miss the plug and missing and poor running generally would result. The correct position, on the other hand gave excellent results all round, and without any serious attempt at super carburation a tick over speed of 300 to 400 R.P.M. could be obtained which compares very favourably with the standard Bentley. The effect of overlap was not considered as very great, and when it is borne in mind that there is 20° on the Coventry Climax as compared with 12° on the Bentley for much the same tick over speed. There would appear to be something in this. Taking into consideration the fact that we are proposing to run with no overlap we think a very good tick over indeed may be anticipated. Starting was stated to be very good, and from power curves sent us some time ago, there is very little doubt that a good low speed torque may be expected. (6) Engine Breathing. We had quite a long talk with Mr. Bertelli on the subject of engine breathing, and he seems to place great stress on the form and shape of the ports. His chief aim appeared to be power output, and he claims that anything which affects the velocity of the gas flow, such as restrictions like valve guide bosses, or bends in the induction ports or exhaust ports, all have an appreciable effect on power output. The type of port used is similar to that shown in Fig. 1, and it will be seen that, save for the slight interruption of the actual valve, there is no restriction whatever to the gas flow. (7) Exhaust Valve Temperature. The scheme shown on Fig. 1 is a rough sketch as near as can be made, to the head in use on the O.H.C. engine which Coventry Climax propose marketing. This engine has not been completed yet, so no results were obtainable, and they did not seem too keen to volunteer details about it. | ||