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).
Spectre Carburation tests carried out on a six-cylinder 20/25 HP engine, comparing different induction systems.
| Identifier | ExFiles\Box 124\3\ scan0257 | |
| Date | 4th December 1934 | |
| To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/CTS.{C. Trot Salt - Carburation} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/CTS.{C. Trot Salt - Carburation}7/KW.4.12.34. SpectreCodename for Phantom III Carburation. Tests have been carried out on a six cylinder engine to determine the relative values of individual arrangements of induction systems, against camshaft overlap, the application of heat, and the size and shape of induction pipe. The engine used is a 20/25 HP. unit, having a Bentley cylinder head fitted, so that a close relation to SpectreCodename for Phantom III arrangements could be applied. We first consider the change which takes place before and after modifying the engine from (1) Standard 20/25 HP. engine to (2) Fitted with Bentley cyl. head and "outside" type of induction system. Considering (1) as the latest production engine; the slow running is steady and reliable from 250 - 300 R.P.M. with tappet clearances of inlets at .004 and exhausts at .006 (hot), which give a resultant overlap of 70° (crank angle). Considering (2): when a Bentley cylinder head and induction system have been fitted, the slow running is no better than that of the complete Bentley engine. This comparison between (1) and (2) gives us the line of investigation which is followed out in this report. The tests are now carried out on a 20/25 HP. engine fitted with Bentley head, and modifications to the induction system working from the standard Bentley type. | ||