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).
Carburettor design, comparing emulsion type diffusers with plain tube jets and the need for an acceleration pump.
| Identifier | ExFiles\Box 5\4\ 04-page245 | |
| Date | 1st June 1932 guessed | |
| -2- HS{Lord Ernest Hives - Chair}/A.L./L.LL.S.R.S.Contd. size than the model Solex we are sending you. The induction branches we think should be the same size as the inlet ports or only a little smaller. We could build up one or two pipes of smaller diameter for tests on the engine. The throttle bore of the carburettors would be the same size as the ports. we would suggest chokes of about 34 m.m. dia. Our experience has been that the emulsion type diffuser - like solex and our R.A. aero carburettors - is better for snap opening than the plain tube jet as used in the Zenith. Petrol standing in the well with air at the back of it is easily lifted into the air stream when the throttle is snapped open. A high fuel level is also necessary. Even then it would probably be advisable to provide for some form of accelerating pump. We must remember that the metering is determined by the design of the diffuser. For good snap opening a plentiful supply of air and adequate air holes in the diffuser are necessary, but for a flat metering curve - i.e. economical consumption at the reduce throttle openings - the reverse is desirable. Therefore we cannot completely satisfy these opposing functions by the diffuser alone. With all sudden changes of engine speed there is always a lag in the fuel supplies to the air, therefore a mixture which is correct for steady conditions becomes lean on acceleration. A throttle controlled pump should actually improve the economy because the normal mixture could be set about weakest maintained. On a 280 miles run on 'Japan' with the twin | ||