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 tests on Duplex manifold and separate exhaust systems.
| Identifier | ExFiles\Box 134\1\ scan0087 | |
| Date | 13th May 1938 | |
| 1129. also. spare T. Rm{William Robotham - Chief Engineer}3/R.{Sir Henry Royce} 13th May, 1938. Dr. J.C. Morrison, James Watt Engineering Laboratories, The University, GLASGOW. Dear Dr. Morrison, Many thanks for your letter of May 12th. Just as we had completed our tests on the Duplex manifold and two separate exhaust systems, the Jaguar came out with this arrangement at the Motor Show. We understand, also, that it is now fitted to some Alvis cars. There seem to be two separate merits in a Duplex exhaust system - (1) With two separate systems it is possible to silence the engine with less back pressure than with a single system. This alone is likely to halve the horse-power drop through silencing. (2) The wave effect on which you have been working seems mainly to be in evidence at the medium engine speeds, and gives a further increased in B.M.E.P. and also a slight increase in top horse-power. We have separated out these two effects by running a common manifold with two outlets and two exhaust systems from there onwards, and Duplex manifolds which entirely separate the front three and the rear three cylinders. The results are somewhat involved. Next time you have an opportunity I suggest you call at the Factory, and we will show you some of the results. Fundamentally, we seem to have got to the point where we can keep our exhaust loss down to about 5% of the total, and, therefore, any further improvement cannot be of a major nature. | ||