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).
Comparison of large 6-cylinder engine performance against proposed 12 and 18-cylinder units following a visit to the U.S.A.
| Identifier | ExFiles\Box 13\4\ 04-page013 | |
| Date | 23th July 1932 | |
| -4- Until we went to the U.S.A. this year, we felt that the big 6 cyl. still had a future against the 12 and 16 cyls. for performance in the large car class. As we pointed out on returning, we are now somewhat doubtful. We considered the Bentley the outstanding example of a refined high performance 6 cyl. engine but we now know that the "8 Litres" sold to the public had not superlative performance (we completely out-pointed one on 27-SK. which had our proposed improvements on it). The Bentley, belonging to Bexley, that lapped at 98 M.P.H. and impressed us so much on the track we find had a higher compression ratio than standard. (The "Standard" was already appreciably worse than 19-EX. for detonation), and the bad slow running was due to over lap on the camshaft, and not carburation, Bm. himself giving 9 M.P.H. as the slow running speed on the road. Therefore, even with four valve/cylinder the best big six we know has only obtained its performance at the expense of R.R. characteristics, whilst its crankshaft presents a problem if the engine is to run at 3750 R.P.M. We therefore feel that our P.11 engine power output development has reached a stage where it will not progress appreciably for the next few years. On the other hand our smaller units have indicated that we can get a considerably higher output/litre from them than from the Phantom whilst retaining R.R. characteristics of slow running and freedom from detonation, the main reasons being that they will stand a higher compression ratio, are smoother, and have a wider speed range. Thus on the results already obtained comparing a twin six composed of two J.1 units, with the best P.11 we know how to make we get :- Unit. Displacement. Clutch BHP. Available at 95 MPH. both units geared present P.11 Std. Open Exhaust. Existing P.11. 7668. 165 B.H.P. Two J.1 Units 12 cyl. 7340 210 BHP. (Up to 220) Three Peregrine Units 18 cyl. 6792 225 BHP. We know the existing taxation difficulties and we appreciate that American competition does not worry us much in England. The above facts are emphasized to shew why we shall not be able to compete successfully with 12 and 16 cyl. cars, and | ||