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 to Rover Motor Co. Ltd. discussing engine performance including gas velocity, manifolds, and valve timing.
| Identifier | ExFiles\Box 127\2\ scan0160 | |
| Date | 20th December 1940 | |
| Rm.{William Robotham - Chief Engineer}S/ML. 20.12.40. S.B.Wilks,Esq., The Rover Motor Co.Ltd., New Meteor Works, COVENTRY. Dear Wilks, Thank you for your letter of the 16th. December. We have got a satisfactory pick-up for slow speed with gas velocity as low as 60 ft/sec. at 1,000 r.p.m., on four cylinders pulling from one carburettor. We have been as high as 117 ft/sec. also at 1,000 r.p.m., when we were looking for maximum economy, but this resulted in a definite loss of power. These figures were obtained on water heated manifolds. We have not found that there is any difference between a well-designed water heated manifold and an exhaust heated hot-spot, when both are warmed up. The water heated hot-spot, of course, takes longer to attain a working temperature. We suggest that your poor low speed torque will be due to valve timing. If you have a larger inlet valve than previously, you will have to shorten it's duration and you will also find that the quietening ramp will have a greater effect on idling than with your old type of engine. We do not know very much about this running after switching off, under small throttle openings. We are however, doing some work on the subject now. Though the exhaust valve is relatively cool it is probably still the hottest surface in the cylinder and as such is not above suspicion. - Continued - | ||