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 modifications and performance tests, detailing changes to address fuel supply issues.
| Identifier | ExFiles\Box 179\2\ img275 | |
| Date | 23th February 1932 | |
| -2- One of the troubles we have had was insufficient fuel at maximum R.P.M. full throttle. The main jet was increased from .125 to .172" without any appreciable difference. We made one experiment by tapping into the petrol chamber below the needle seat and measuring the depression, we found that at 3000 R.P.M. we measured a depression of .35". Following this, the three feed holes in the carburetter were increased in number to six. After carrying out these alterations we found that at 3000 R.P.M. there was no depression, the supply being sufficient. Being a low depression carburetter and consequently low suction upon the jet, the petrol passages before and after the needle valve should be as unrestricted as possible. As regards the distribution, we have tried a packing so that the butterfly throttle is farther away from the small choke. This made it very much less sensitive to the throttle position and the distribution throughout the whole range is now satisfactory. GENERAL PERFORMANCE. We think that this carburetter promises to be very satisfactory and we expect that ultimately it will become our standard carburetter for all cars. We are now producing two more carburetters so that tests can be carried out simultaneously on the road and the blower rig. HS.{Lord Ernest Hives - Chair} | ||