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).
Improving slow running for the Spectre Induction System by modifying camshaft overlap.
| Identifier | ExFiles\Box 4\1\ 01-page173 | |
| Date | 4th December 1934 | |
| To E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Nor. c. to By.{R.W. Bailey - Chief Engineer} 24694 Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}G/KW.4.12.34. SpectreCodename for Phantom III Slow Running. Attached is a report on work we have so far carried out on the 20/25 engine fitted with a Bentley head to reproduce the SpectreCodename for Phantom III Induction System. Our original results were complicated by the fact that this system is very sensitive to the amount of camshaft overlap. Having separated the camshaft from the carburation we got more consistent results. It will be seen that we do not now recommend either small bore induction pipes or totally heated induction pipes, as both these lose power without improving slow running appreciably. It would seem that the only modification we can make to the existing SpectreCodename for Phantom III design with four carburetters to give appreciable improvement is to reduce the camshaft overlap. We shall hope to have the engine in the car with the short duration camshaft next week. We are aware that we still know very little about slow running and how it is obtained, because the straight 8 Buick with the up-draught carburetters, which is our model for idling and even pulling at low speeds, has more overlap than the Bentley as will be seen from the attached diagram. (handwritten: Tommy) Unfortunately we have no details at present of the Series 40 Buick with the down-draught carburetters, which approximately represents the Wraith. Its slow running, however, is not as good as the Buick with the up-draught carburetters. We have written to America to see if we can get an opinion as to what they really think of down-draught carburation in relation to slow running. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||