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).
Analysis of downdraught carburettor percolation issues and proposed solutions including choke jacketing.
| Identifier | ExFiles\Box 173\4\ img185 | |
| Date | 1st January 1936 | |
| (6) Not yet obtainable but the solution. Having noticed that an updraught never suffered from this trouble and the engine will always restart, they looked for peculiarity of downdraught carb. Measurement of the temperature of various parts of a downdraught carb. after the engine had been stopped gave as approximate results in °F.{Mr Friese} Percolation only is troublesome if A.{Mr Adams} exceeds B. They have therefore jacketed the choke and pass petrol through this on its way to the float chamber, thereby lowering the temperature of the choke and increasing it slightly in the float chamber. This they say solves the problem but is not yet on the market. As regards automatic chokes, they do not consider the electrical unit much superior to the exhaust heated type and add that neither of them has been arranged for a manifold having water hot-spotting. No American car has this, and work requires doing to get the choke right for such slow warming of the manifold. | ||