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).
Slow running (idling) issues with the Spectre engine and experiments to resolve them.
| Identifier | ExFiles\Box 4\1\ 01-page139 | |
| Date | 27th October 1934 | |
| 4694 To E.{Mr Elliott - Chief Engineer} from Ha/Rm.{William Robotham - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} Ha/Rm.{William Robotham - Chief Engineer}3/KW. 27.10.34. SpectreCodename for Phantom III. Two further points have arisen in connection with the SpectreCodename for Phantom III engine - (1) Slow Running. We are having considerable difficulty in obtaining good slow running from the SpectreCodename for Phantom III even with tappet clearances which eliminate the overlap in the camshaft. Experiments carried out on the SpectreCodename for Phantom III fitted with a 20/25 camshaft and using two SpectreCodename for Phantom III carburetters indicate that we cannot get the desired degree of slow running. In view of the fact that with a similar carburetter when we pass the mixture through the block we get satisfactory idling, we fitted two extensions to the SpectreCodename for Phantom III carburetters, about 5" long, and water-heated these. The results indicated a very marked improvement in idling. We therefore feel that at present the mixture is collecting in the bottom of the SpectreCodename for Phantom III pipes where the gas velocity is very low due to idling, and the hot spot is not sufficiently intense, being water heated, to vaporise this condensed fuel which ultimately finds its way into the cylinders, causing hunting. This appears to be accentuated more on the SpectreCodename for Phantom III than on the Bentley owing to the fact that the induction system is downhill from the carburetter onwards We are experimenting with a pipe on the Bentley in which the carburetter is definitely lower than the cylinder ports, and hope that with this arrangement we may be able to get slow running without moving the carburetters further away from the cylinder block. We should, however, like you to consider what can be done from a design point of view to improve this feature. Apart from the idling the SpectreCodename for Phantom III system seems to be satisfactory from the point of view of distribution, snap opening up and intake silence. | ||