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 suggesting fuel testing procedures to determine knock ratings and fuel requirements for an engine.
| Identifier | ExFiles\Box 150\1\ scan0062 | |
| Date | 7th November 1935 | |
| TO W. A.{Mr Adams} Robotham Esq. (Rolls-Royce Ltd.) 2. DATE 7-11-35. If I may offer a suggestion, I would take the same engine under identical conditions and vary the compression ratio and determine the fuel requirements for incipient detonation in each case. For these reference tests I would not use benzol as the anti-detonant, since (as I am going to suggest later) it is rather unstable and does not correlate closely enough upon the C.F.R. Motor Method. Instead, I would use either 80 octane Ethyl or 87 octane D.T.D.230 as the high anti-knock, and blend this with a good No.3 grade petrol as the knocking constituent. If you were to keep samples of each blend then we could have these knock tested for you. In doing similar tests I have found that a convenient (but rather rough) method is to feed the fuels through two separate flow meters simultaneously, so that the proportions can be varied quickly and at will. As requested I am sending you herewith half a dozen copies of the benzol response curves to which you refer, and in this connection I would mention that the octane ratings are shown as C.F.R. Motor Method, and you will notice that a mixture of 50% of benzol with a No.1 or No.3 fuel gives a rating of between 78 and 80. Actually it was found that the C.F.R. Motor Method tended to de-rate benzol as measured in the American motor cars to the extent of about one to two numbers, depending on the concentration. Very roughly, a high benzol blend showing 80 C.F.R. Motor Method will probably rate 81 or 82 when measured, say, in your Bentley at about 7 to 1 ratio, although it is possible that under severer conditions, say 10 to 1 ratio, the benzol blend may depreciate somewhat in knock rating. Yours very truly, Hassett HF{H. W. Frost - Coachwork Inspector}/BB | ||