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).
The performance and testing of a Double Choke Stromberg Carburetter, detailing starting issues, road tests, and fuel performance.
| Identifier | ExFiles\Box 91\1\ scan0388 | |
| Date | 14th August 1936 guessed | |
| -3- Carburation - Double Choke Stromberg Carburetter N.Sch.4882 We are of the opinion that this carburetter is a distinct improvement on the previous arrangement of four carburetters. The maximum acceleration is not quite so pronounced, but we seem to gain a little at the top end i.e. maximum speed. There is no doubt that everything is far more accessible, and that everything now has a chance to get a fair share of the air circulated by the fan. Despite this, however, we have been having trouble in starting when the car has been left standing after a fast run. We put this down as being a direct result of the high under-bonnet heats encountered in France. This, after a period, heated up the system and caused petrol vapour to form in the pipe lines and pumps. The pumps were subsequently moved and placed on the frame side under the floorboards. We found this completely cured our difficulties of starting when hot, and considerably assisted in curing the misfiring due to starvation after prolonged high speeds in hot weather. Under running conditions the trouble has not been so pronounced, and has only been experienced under very extreme conditions, but we point out that cars will run under these conditions in England, and that it is quite possible to get these condition on a hot Summer day. * We went down to Mt. Ventoux in the Basse Alps during the trip to try and get extreme conditions of hill climbing, etc., but unfortunately we encountered cold weather and were not able to obtain any really useful information. During these tests the throttle stuck open, and was traced to there not being sufficient clearance between the throttle choke pick-up and the throttle spindle lever. There is a thin friction washer between the faces, and this was binding due to tightness. On removing this washer, no more trouble was experienced. We were unable at first to purchase anything but cheap petrol, and found that this produced violent detonations throughout the climb. Subsequently we tried the climbs with Esso, and produced detonations up to 18 M.P.H. but on using Azure no detonations could be detected. We ascertained that whereas Azure petrol remains constant, the octane figure for Esso slightly varies at different pumps. | ||