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).
Issues found during tests of a pilot jet on a 40/50 engine, particularly concerning cold starting.
Identifier | ExFiles\Box 74\2\ scan0031 | |
Date | 13th September 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} c. to EP.{G. Eric Platford - Chief Quality Engineer} c. to EWT. for R.R. Inc. X4387 Hs{Lord Ernest Hives - Chair}4/LG13.9.21. RE. PILOT JET. X4387. We have carried out a number of tests with the pilot jet instructed on LeC.1418 on a 40/50 engine. We find that the proportions of this jet do not allow sufficient mixture to pass to start the engine from cold. In order to get a positive start when the engine is cold, we have proved that the pilot jet must be capable of running the engine light at about 600 R.P.M. when the engine is hot. As the pilot jet was first instructed, we could not get run the engine with it at all. After we had enlarged the venturi and the various holes and passages to the maximum amount, we could get the engine to run at 400 R.P.M. when it was thoroughly hot but we could not start the car up with it if it had been left outside all night. It is not that one particular part is restricted so much that the unit as a whole is too small. We are not certain, even when it is made larger that it is going to give the desired results. The point we do not like is the fact that in order to enrich the mixture when the engine us started in very cold weather, the volume must be cut down. This is just the opposite to what is required because in the very cold weather, when the engine is stiff to turn, it is then the maximum quantity of mixture is required. As on the 40/50 it is only to be used for starting and it will be shut off immediately the engine is running, we think it is rather contd:- | ||