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).
Improving heat transfer to induction pipes and modifications to manifolds and carburetors.
| Identifier | ExFiles\Box 124\1\ scan0171 | |
| Date | 28th June 1939 | |
| -2- We require as much heat on the pipe as possible at low speeds. It has been said that our water heated hot spots are a draw back in this respect, but in our experience the available heat either from contact with the exhaust manifold, or from direct exhaust port connection is very limited. When we first fitted the Stromberg carburetter to the 20/25, both inlet and exhaust manifolds were on the same side of the engine, and a large area of the centre portion of the inlet manifold was contact heated by the exhaust manifold. We carried out a direct comparison between exhaust and water heated hot spots, and found that at low speeds where the heat is needed, there is more available heat from the circulating water, than from the exhaust. Temperatures were taken on the inside walls of the pipe. With reference to capacities of the induction pipe, the size of the box below the riser, and the main bore of the pipe should be as small as can be reasonably allowed. A new design of pipe should be drawn incorporating - (a) Main bore of 1.500 dia. (b) Reduced capacity in the tee bend. (c) Improved shape of drain below (b). (d) Larger hot spot as sketch Rm.{William Robotham - Chief Engineer}590. The connection from the cyl. head might be improved, and the water must go all round the pipe. The height of the riser should be .750 and should be heated by taking the casing of the hot spot as near to the carburetter flange as possible. An alternative to this design should be available as a separate instruction as follows - After producing castings from the above the pattern should be modified in the inlet branches to produce the same effect as the Buick. That is to have graduated elbows from the front end, to bring the main bore of the pipe into a horizontal plane in relation to the angle of inclination of the engine in the frame, when the car is fully loaded. With reference to the duplex carburetter on the six cylinder engine. If the new design of induction pipe for the eight is approved, the duplex pipe available for the six should be brought into line accordingly. | ||