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).
Bentley engine ignition timing tests and recommendations based on different fuel octane ratings.
| Identifier | ExFiles\Box 3\4\ 04-page248 | |
| Date | 25th March 1933 | |
| X45536 E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} C. to BY.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}5/KT. 25.3.33. BENTLEY IGNITION TIMING. We have carried out a number of road tests to determine the optimum ignition timing of the Bentley engine with 6.3/1 c.r. We recommend that this timing should be 13º B.T.D.C. With the turbulent head and a clean engine this means that we can run with practically no detonating on Shell-Mex fuel which has an octane value of 64-66. Standard number one petrols such as Shell have an octane rating of 68-70 and which means that the Bentley car will be capable of running on any number one fuel with 10,000 miles of carbon in the engine, without excessive "pinking". Existing Ethyl petrol has an octane rating of 74 and it is proposed to raise this to 78 in the immediate future. If a petrol of 78 octane rating is standardised for general distribution, it means that we can appreciably increase the c.r. of the Bentley above 6.3/1 the ratio of the first cars which are to be produced. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} | ||