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).
Unvapourised fuel surging in the Induction System B.80 No.5 Unit.
| Identifier | ExFiles\Box 122\4\ scan0234 | |
| Date | 28th June 1939 | |
| 1036 & 1044 To By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to Da{Bernard Day - Chassis Design}/Jnr.{Charles L. Jenner} c. to By/Ald.{F. Allwood - Experimental Design} c. to Da{Bernard Day - Chassis Design}/Mc. Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation}14/JH.28.6.39. Induction System B.80 No.5. Unit. Carburetter. Stromberg type AA.{D. Abbot-Anderson}25 (Throttle 1.437). Induction pipe. EB.4835 Main bore 1.750 dia. riser 1.437 dia. Our main problem is concerned with the heavy unvapourised fuel surging in the pipe at low speeds full throttle. Running open exhaust on the bed this is distinguished as follows. At say 750 r.p.m. full throttle, intermittent over rich charges are evident by puffs of black smoke which issue from all the exhaust ports, but in no particular sequence. On throttling back at this speed, the loose petrol is taken into the cylinders to such an extent, that at certain intervals, unburnt petrol occasionally issues from the exhaust port. This phenomenon is a characteristic of downdraught carburation. It is present on the Wraith, but only in a minor degree. It is completely absent on the Bentley. The main factors which influence this building up at low speeds are as follows, in order of their importance. (1) Temperature of the induction pipe walls, in particular the tee bend adjacent to and including the riser itself. (2) The capacity of that portion of the pipe immediately after the riser. (3) The main bore of the induction pipe. Of these points, the following can be said :- | ||