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 Engine, comparing compression ratios with the Cadillac 16 and considering alternative timing proposals.
| Identifier | ExFiles\Box 4\1\ 01-page075 | |
| Date | 29th June 1934 | |
| To E.{Mr Elliott - Chief Engineer} c. to AG. c. to Mor. c. to Hy.{Tom Haldenby - Plant Engineer} c. to W/Int. SpectreCodename for Phantom III Engine. With reference to E.4/HP.23.6.34. The Cadillac 16 is supplied in three compression ratios, 5.1 : 1; 5.4 : 1; and 5.7 : 1. 5.7 : 1 is the highest that is sold to the public. The confusion appears to have arisen owing to the fact that in our Hs{Lord Ernest Hives - Chair}/Hs.{Lord Ernest Hives - Chair}4/KM.18.4.34 we quoted Cadillac M.E.P. figures taken with a Compression ratio of 6 : 1. This was purely an experimental engine. The reason we quoted it was because it was the same compression ratio as the Bentley and therefore gave the best basis for comparing camshafts and carburetter systems. With regard to the timing you are proposing for the SpectreCodename for Phantom III alternative, this certainly should be of considerable interest. We think you are certainly justified in going to a longer duration than the Cadillac, they have not the advantage of a 4-speed gearbox. Actually the overlap is the point which interests us most as this dictates the slow running. We do not think much disadvantage results from inlet closing position as on the 20/25. The exhaust opening early may make silencing more difficult, we are making some experiments to determine if this is so. Hs{Lord Ernest Hives - Chair}/Hs.{Lord Ernest Hives - Chair} | ||