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).
Tests on the vacuum feed system, focusing on suction connection positions and their effect on engine idling.
| Identifier | ExFiles\Box 40\4\ Scan269 | |
| Date | 19th October 1927 | |
| HS{Lord Ernest Hives - Chair}/AJLl/LG19.10.27. VACUUM FEED. With reference to OY2/R/92727. We have carried out tests to investigate the points raised in this memo. (1) TESTS WITH ENGINE IDLING (car stationary). The suction elbow of the Autovac tank was connected up to the induction pipe at two points, viz: the standard position and the base of the starting carb. A three-way tap was inserted in the circuit making it possible to use either position on the induction pipe at will. Subsequent tests shewed conclusively that the present position of the suction connection on the induction pipe is definitely superior to a connection at the base of the starter carburetter, in the matter of affecting the slow running of the engine during the 'dumping' period. This result held good on two cars either using the now standard automatic restriction in the suction elbow or the old standard plain suction elbow. A test was also made in which a restriction in the form of a small hole .065" dia. was placed in a plain suction elbow. This gives the same effect to the Autovac tank as is present in the Stewart Vacuum unit. Under this condition the superiority of the standard induction connection was not so definitely marked, but it was still superior to the central connection. Under standard Autovac conditions, the effect of connecting the vacuum line to the centre of the induction pipe is to stop the engine entirely when the 'dumping' period occurs, (the engine speed being equivalent to 5 m.p.h. road speed), whereas only slight interruption takes place with the vacuum line connection in the standard position. Further tests were carried out by cutting out different cylinders to ascertain which cyls. are richened up during the 'dumping' period when either vacuum connections are used. (a) Std. position of suction connection on induction pipe. The engine was runs perfectly regularly during the dumping period on Nos. 1, 2 and 3 cyls., indicating that these are not richened up sufficiently contd :- | ||