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).
Describing a new auxiliary pilot jet, its installation, function, and advantages over the one fitted to the 6.EX Car.
| Identifier | ExFiles\Box 74\2\ scan0029 | |
| Date | 23th August 1921 | |
| To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair} c. to CJ. c. to E.{Mr Elliott - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to BY.{R.W. Bailey - Chief Engineer} X4387 Hs{Lord Ernest Hives - Chair}3/LG23.8.21. AUXILIARY PILOT JET. X.4387 We are sending to Mr. Royce a small pilot jet which we made some considerable time ago. It was suggested by Mr.Hancock who assists me. We have found this jet to work exceedingly well on experimental cars. This was made at the time we found that the simple pilot jet similar to what is fitted to 6.EX Car suffered from not having means of regulating the mixture and also that it was not positive enough in keeping the engine running. The other advantage in this scheme is that it is very much less costly to fit to existing cars. It replaces the present priming cock on the induction pipe. It is necessary to remove the ball valve from the primer fitting on the float chamber and use that same connection. The primer pipe is then used for the petrol supply pipe to the auxiliary carburetter; this provides a filter for the small jet. We have found that having the throat operated by the suction of the engine does give us a small carburetter for the initial starting and a large enough carburetter for the engine to run vigorously when once it is started up. The advantages we have found in this pilot jet compared with the one on 6.EX Car are as follows:- 1. Greatly reduced cost of fitting. 2. More accessible. 3. Convenient and simple form of regulating the mixture strength. contd:- | ||