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).
Engine detonation, comparing Ethyl and Benzol fuels, and discussing ignition timing adjustments for Bentley cars.
| Identifier | ExFiles\Box 150\1\ scan0069 | |
| Date | 11th November 1935 | |
| -2- Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}6/KW.11.11.35. The attached curve gives values for Ethyl against Benzol mixtures from which it will be observed that the ordinary Benzol mixture does not compare with Ethyl in subduing detonation. We have inserted figures which roughly indicated that if a customer persisted in using a No.3 grade fuel, we could not usefully give him more than 5 1/2 - 1 compression ratio. We predict, however, that it is only a matter of time before Ethyl will be universally used in fuels provided for touring cars. If a Bentley engine in a clean condition detonates badly on No.1 petrol, then there is something wrong. Actually, owing to the ignition advance characteristic, pinking is more likely to take place from round about 50 m.p.h. than at any other speed. If for any reason the automatic advance is not functioning satisfactorily, this may cause pinking. If the ignition timing is not the same on all 6 cylinders obviously those with the advanced timing are more likely to pink. The attached note explains how this can be caused by a bent governor spindle. In the next Quarterly Complaint list we should like every complaint of pinking to be explained, so that we can form an opinion as to whether the trouble is mainly through a customer refusing to use Ethyl, or to some defect in the ignition adjustment. In the meantime, development work is proceeding to reduce the tendency to detonate at 50 m.p.h. We think that it is the duty of depots to educate Bentley owners with regard to the value of Ethyl in suppressing detonation. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||