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).
Engine performance analysis, including issues with noise, detonation, and head design.
| Identifier | ExFiles\Box 113\5\ scan0214 | |
| Date | 13th February 1939 guessed | |
| -6- Heat Flow to Coolant. A test was run over the speed range using a standard Bentley 4¼ radiator, to determine the heat to the cooling water. This came out at an approximately constant figure of 75% of the BHP increasing at high speeds to 80% and at very low speeds to over 100% General Remarks and Conclusions. (1) Power and Performance. The open exhaust power is excellent showing a gain of over 20% over Bentley 11. Unfortunately, however, with a standard exhaust system this power gain is reduced to about 9% and only a very slight gain in performance is experienced on the road. Tests on various silencing systems have shown it possible to materially reduce this loss, but no road work has been done, and it is not known whether this gain can be realised, and yet maintain the standard of silence required. Also the effect of the increased power provided by the modified exhaust system, on the general performance of the car has not been investigated. (2) Noise and Smoothness. In a chassis, the engine seemed fairly smooth, but tappet and valve gear noises were very evident, detonation was worse, and the chain drive was inclined to be rather obvious. No serious development work was done on the road, only some 4000-5000 miles being covered and it is not considered that any of the troubles experienced are at all insuperable. The tappet noise was considerably amplified by the method of fixing the rocker cover, and there is little doubt that a modified camshaft with improved silencing toes and reduced lifts would go a long way to cutting down the noise trouble. (3) Head Design. The head required modification, with a view to improving the detonation characteristics by firing towards a ~~cooling zone~~ cooler, and also an attempt should be made to cure the trouble due to joint leaks by modifications to studding. It also appears that the construction of the head and rocker mechanism is unduly complicated and very expensive, and in the event of the job being taken up again consideration should certainly be given to simplifying and cheapening the design of the head and the valve gear. (4) Breathing. The breathing properties of the head are so good, that it is anticipated that a considerable reduction would be possible without | ||