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).
Alterations to a carburetter silencer to improve silence and regain power, including performance test results.
| Identifier | WestWitteringFiles\U\August1930-November1930\ Scan144 | |
| Date | 22th October 1924 | |
| -2- tube 94%. Two further alterations are carried out, (1) two layers of 20 mesh wire gauze are wrapped round the innermost baffle tube; this does not give any appreciable power drop but improves the silence. (2) Eight holes .375" diam. are drilled through the top end piece to relieve the air valve restriction. The air valve suction does not require so much baffling to achieve silence as the main air intake suction so that we can regain a small amount of power without any appreciable increase in noise, therefore some of the air valve suction is not taken through the two innermost baffle tubes. We cannot take away any one of the baffle tubes without very appreciably increasing the suction noise. The power loss over the standard carburetter is shown on the attached graph and amounts to 6.5% at 3000 R.P.M., to 3.5% at 2000 R.P.M. There is no loss below 1750 R.P.M. By drilling the air valve additional relief holes an increase of 3½ HP. at 3000 R.P.M. is obtained when compared with the fully silenced carburetter, it makes no difference below 2000 R.P.M. The effect of this power loss was carefully investigated on Brooklands; the effect on lap speed is as follows, a series of tests was carried out to determine the effect of each unit of the silencer on the lap speed. Tests carried out on 2H-EX., cut out closed, plain bonnet fitted. | ||