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).
Use of Tetra Ethyl Lead fuel, octane ratings, and engine performance tests.
| Identifier | ExFiles\Box 27a\4\ Scan021 | |
| Date | 17th November 1932 | |
| S/W. To Hs.{Lord Ernest Hives - Chair} from Lp.{Mr Lappin} Copy to Wg.{Mr Gill - Financial Director} " " Rg.{Mr Rowledge} " " RP. " " Lf. 8188r. Lp.{Mr Lappin}9/LAM.17.11.32. Re: TETRA ETHYL LEAD. With reference to our conversation re use of T.E.L. Fuel, the 100 hour test we carried out on this fuel is regarded by the Air Ministry as a fuel test and not a type test, and to clear the engine for using T.E.L. abroad, it is necessary to ask Major Ross to give you an amended type test certificate based on the A.I.D. Reports as he did not see the strip of the above engine. This I think would be granted to cover the use of a straight run spirit to which Tetra Ethyl Lead can be added up to a maximum of 4 cc's per gallon so that the resulting fuel has a knock rating of not less than 76 octane at 100° C. Whilst on the subject of fuels, the best American fuel used in the high performance engines has a knock rating of 86 at 190° C. This gives them a definite advantage over us in this country and in selling engines abroad they could quote greater horse power outputs and insist on fuel of 86 octane being used. I asked Lf. to suggest that you carry out a test to ascertain what additional output could be had from the "Kestrel" engine using a fuel 86 octane at 190 (which under Air Ministry test would probably be 90 octane) for the same detonation as obtained running the engine on D.T.D. 134. Our Air-cooled competitors are having trouble on lead fuel and I think this is a good reason for our pushing it with energy. You might consider it worth while out asking Hawkers to run their P.V. "Hart" and "Fury" continuously on T.E.L. in order to get air experience. Lp.{Mr Lappin} RECEIVED NOV 18 | ||