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 correct setup of low-speed jets and air ports in a carburetter.
| Identifier | ExFiles\Box 66a\1\ scan0076 | |
| Date | 26th November 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. -4- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/ACL/LG26.11.25 up correctly. (1) That the low speed jet is adjusted to give a correct mixture at that engine speed or depression, when the diaphragm is just on the point of admitting air through the diaphragm ports in the high speed choke. (2) That the air ports in the air valve just start to open after the high speed jet starts to spray. The reason for the importance of these two points can be explained as follows :- If the low speed jet is adjusted to give smooth running - and consequently what we should call a correct mixture - at a speed below which the diaphragm starts to lift and admit extra air, we shall find that with a slight increase of speed above this setting the mixture will become noticeably rich. This richness will be very marked for the reason stated in the third paragraph. The following diagram - from an actual experiment on a New PhantomCodename for PHANTOM I carburetter - clearly shows the extent of richening when the low speed jet is set before the air valve starts to lift. MADE AT CROXLEY contd :- | ||