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).
Investigation into a carburation 'luffing up' complaint on car 199-RY, resolved by reducing the low speed jet size.
| Identifier | ExFiles\Box 18\5\ Scan059 | |
| Date | 24th April 1935 | |
| To C. c. to H.{Arthur M. Hanbury - Head Complaints} c. to Ld. c. to Dr. +761 HS{Lord Ernest Hives - Chair}/Wym.{G. Harold Whyman - Experimental Manager}16/KW. 24.4.35. Re 199-RY. Romero's Car. We have been investigating the carburation complaint on the above car. It was our old complaint of "luffing up" at 30 m.p.h. on top gear, although in this particular case the trouble was very slight and could only be produced once or twice in a matter of 40 or 50 miles. We examined the carburetter thoroughly and found that all the modifications had been fitted and that the jet settings and level etc. were correct, and that there was no apparent reason for the carburetter not functioning correctly. We fitted an old experimental carburetter to the car, and it ran perfectly, so we removed the whole of the "innards" from the carb. jets, diffuser, air valve etc., and fitted same to the carb. on 199-RY, but even this did not cure the trouble. This meant of course that there was a slight variation of some description in the casting, or in one of the many holes and passages drilled in the casting. It is almost impossible to say exactly what, because it means scrapping the casting to find out, so having made a pronounced improvement by reducing the low speed jet size from .031" to .025" we decided to reduce it still further to .020". This entirely cured the trouble, and is in no way detrimental to the carburetter. We would like to add that should this trouble occur again on any other Ph.II cars, if reducing the jet size to .025" does not entirely cure the trouble, we would recommend that a .020" jet be fitted. HS{Lord Ernest Hives - Chair}/G.H. Whyman. | ||