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).
Letter discussing experiments and results with different types of induction pipes, particularly heated versus unheated.
| Identifier | ExFiles\Box 75\2\ scan0252 | |
| Date | 9th August 1921 | |
| CC Mr. Pelnap Mr. Nadin. X2758 August 9, 1921. OY1/G9.8.21. Mr. Claude Johnson, Managing Director, Rolls-Royce Ltd., London, England. Attention Messrs. Royce & Hives. Dear Sir, Re Induction Pipe on 4.EX. X.4305 X.2758 X.3764 Referring to Hs{Lord Ernest Hives - Chair}2/LG6.7.21, we quite agree with Mr. Hives in believing that the heated pipe we have used is not the final word by any means. We have found, however, not once but in several cases, a marked improvement in running when the heated pipe has been fitted on existing cars. Mr. Hives wrote in regard to his early experiments with this type of pipe, that he had obtained good results with three out of four pipes but was unable to reproduce the results on the fourth. We think that in view of the fact that we had nothing to go on except the results of our own experiments, and that we met serious trouble with pre-ignition with the other type of pipe, jacketted at the Tee, there was no alternative but for us to adopt for the time being the one type of induction pipe which had shown us an improvement in a number of cases without causing pre-ignition. We are not in a position to judge whether under American winter conditions, the improvement, as Mr. Hives claims, is solely due to the higher velocity in the manifold rather than the heat, except that we made up a manifold with unheated 1" through pipe and did not get particularly good results from it as regards loading up. Whether the thermometer in the pipe is a reliable indicator, because of the wet gas flowing against it, we do not know, but the effect of evaporation on the bulb would be to lower the temperature so that if the thermometer reads higher on one test than another, one would suppose that the gas is either hotter or dryer, either of which is desirable. We may mention that the pipe on 4.EX, as already stated to Mr. Hives has collecting elbows within the exhaust outlets of Nos. 1 and 6 cylinders. This was only done on 4.EX and it contd:- | ||