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).
Comparing four different manifold systems and their effect on exhaust pressure and power output.
| Identifier | ExFiles\Box 72\4\ scan0341 | |
| Date | 28th March 1924 | |
| R.R. 493A (40 H) (8L 42 12-7-23). J.H.D. EXPERIMENTAL REPORT. Expl. No. 9230 REF: Hs{Lord Ernest Hives - Chair}/ACL/28.3.24. (4) One large diam. manifold - 3.75" dia. at outlet end. Light spring diagrams are given for each of the above four systems. With the standard manifold it is seen that the exhaust reaches a pressure of 8.05 lbs./sq.in. near the end of the exhaust stroke falling to atmospheric after 30° of induction stroke. The two factors causing this 'pressure bump' are apparently interference of exhausting periods in the common pipe and resistance in exit from manifold. The larger diam. common manifold has the same characteristic but to a less marked degree. The minimum exhaust pressure bump is given with these manifolds arranged to prevent interference of exhaust periods of the different cylinders. Effect of power output. The compression pressures and indicated vol. efficiencies are approximately the same for each of the four systems. The standard system actually gives slightly higher values. It is noticeable that the power varies inversely with the exhaust pressure bump. It seems apparent that with a large exhaust pressure bump a certain amount of exhaust gas at high temperature is expelled into the induction pipe which is again drawn into the cylinders with the fresh charge. This lowers the M.E.P. and probably raises the temperature of the cycle. From our tests the best results were obtained by contd:- | ||