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).
Discrepancy in valve timing and requesting revised figures and permissible variations.
| Identifier | ExFiles\Box 33\4\ Scan068 | |
| Date | 1st August 1921 | |
| Oyl - G 1821 August 1, 1921 Mr. Claude Johnson, Managing Director, Rolls-Royce Ltd., London, England. Attention: Works Committee. Dear Sir:- Re: Valve Timing. We wish to bring to the attention of the Works Committee the considerable difference between the valve timing given on the drawings and the actual valve timing to which the Test Department, both at Derby and here, is working. We should like to receive from the Works Committee a set of revised figures for valve timing, giving the best practice found from actual test, so that we can insert these on our drawings and on the flywheel marks. These should be the ideal correct timings; but we should also like to be told (1) the permissible variation from these timings, (2) the "starting point" of the timings - that is, the point which it is considered most important to keep correct (understood to be "Inlet Closing") (3) the permissible variation between different cylinders of any engine, and (4) the difference which should be made in valve timing between high and low compression engines. (Here we may suggest that for highly detonating fuels, such as are used in America, it is desirable to have a later inlet closing point on high compression than on low compression engines, so as to cut down the maximum explosion pressure at low speeds full throttle, in order to avoid "knocking". This is recommended by engineers here, the cylinder being allowed to pump back some of its gas into the inlet manifold at slow speeds.) | ||