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).
The effects of air silencer and induction pipe modifications on engine performance.
| Identifier | ExFiles\Box 3\6\ 06-page290 | |
| Date | 29th October 1934 guessed | |
| -2- With the air silencer removed and just the bends fitted the larger Bend gives a slight increase over the standard Bend at 2500 r.p.m. but is below the power output given when the carburetter intakes are open. As shewn on curve B.V.56, there is a peculiar effect of increased power with the Bends fitted over the case where the intakes are open at speeds up to 2,000 r.p.m., and here again the capacity effect and the possibility of "Ramming" no doubt accounts for it. We found that the complete air silencer reduces the power output by 2.8% at 4000 r.p.m., 4.1% at 4250 r.p.m. and 5.5% at 4500 r.p.m. We intend to try the effect of a larger bore through the main portion of the air silencer to see if we can improve the power output, but we expect we shall lose a certain amount of power in order to maintain the present standard of silence and also due to the fact that with the air silencer fitted we introduce another change of direction for the air flow. We also tried the effect of a smaller bore induction pipe but from the curves obtained our tests on the bed contradict the tests carried out on the road. From the tests on the bed we found that with the smaller bore induction pipe we lost from 2.2% to 4.2% at speeds from 4000 r.p.m. up to 4500 r.p.m. and there was no gain in M.E.P. at the lower speeds when compared with the standard induction pipe. On the track the maximum speed of the car was 86 M.P.H. with both the standard bore pipe and the small bore pipe, from the power curve we would not expect the maximum speeds to vary greatly as at the corresponding engine speed the lower loss is only in the region of 2% to 3%. On acceleration tests, however, the car has been proved to be definitely better with the small bore pipe at "snap" opening of the throttle from 10 m.p.h. but this is probably due to the reduction in capacity of the pipe and the increased gas velocity. A comparison of the two induction pipes is shewn on curve B.V.57. | ||