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).
Letter from Ethyl Export Corporation discussing fuel knock-rating in relation to engine design and compression ratios.
| Identifier | ExFiles\Box 150\1\ scan0061 | |
| Date | 7th November 1935 | |
| CABLEGRAMS: ETHYLPORT, LONDON. X1282 TELEGRAMS: ETHYLPORT, SOWEST. ETHYL EXPORT CORPORATION Incorporated in the State of Delaware U. S. A.{Mr Adams} with limited liability. THAMES HOUSE, MILLBANK LONDON, S.W.1 Telephone: VICTORIA 5520 Head Office: 135 EAST 42ND STREET NEW YORK, U.S.A 7th November, 1935. Your ref: Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}24/KW. W. A.{Mr Adams} Robotham, Esq., Experimental Department, Rolls-Royce Ltd., Nightingale Road, DERBY. Dear Mr. Robotham, I wish to acknowledge receipt of your letter of the 6th November in Mr. Banks' absence on the continent. He is expected back at the beginning of next week. With regard to the two samples of fuel on which you would like to know the knock-rating, I know that he would only be too pleased to get these for you, but at the moment I do not know Mr. Banks' movements, though I believe he is coming up to Derby next week sometime. If he is not, I myself will be in the midlands towards the latter part of the week and could come across and see you and collect them. With regard to your query concerning the possibility of giving a general correlation between the knock rating of the fuel and compression ratio, I am afraid it is not possible to do this in general terms. The correlation depends upon a great number of factors, of which the following are the most important:- 1) combustion chamber design 2) cylinder size 3) degree of heat conductivity, both laterally and to the cooling water (i.e. conductivity of head material, degree of carboni-sation and silting of the jackets) 4) mixture strength, mixture temperature, volumetric efficiency, etc. To epitomise this, it is obvious that an engine designed with a highly efficient combustion chamber will, in the first place, stand a greater h.u.c. on a given fuel, and also reap more benefit per octane number increase than an engine with a poorly designed and badly detonating head. The curve you want is a particular characteristic of each individual engine, and I would suggest that it would be very interesting if you could do some ratings on some of your own engines, of which you have undoubtedly got many alternative compression ratios. | ||