Comparison of external and internal fast idle systems for an engine's electrical choke unit.
| Identifier | ExFiles\Box 123\1\ scan0004 | |
| Date | 23th August 1939 | |
| -2- Rm {William Robotham - Chief Engineer} /TAS. {T. Allan Swinden} 9/MH. {M. Huckerby} 23.8.39. (2) that a good cold start is obtained, and that the choke opens sufficiently rapidly to prevent bad richening up before it is fully open. This, of course, may lead to another disadvantage, for since duration of choke opening is due solely to time and not temp-erature the carburetter may go weak when the engine is started under extreme cold conditions. The electrical unit may be built up in two ways:- A. {Mr Adams} With an external fast idle system operated by a throttle stop on stepped cams. B. With an internal fast idle operated by a lever attached to the choke butterfly itself. A has obvious disadvantages for an R.R. product, since the accelerator pedal must be kicked before starting cold, and if started and left untouched the engine will still be running at anything around 1000 r.p.m. after half an hour. B. gives a progressive slowing down as the choke butterfly opens. Under extreme cold start conditions this will accentuate the weakness due to the choke opening too rapidly, this being very noticeable on 11.B.V. which in other respects behaved very well in the cold chamber at 18°F. {Mr Friese} Good hot starting and absence of richening up under normal start conditions are an alternative to absence of weak-ening off under extreme cold start conditions, and a compromise has to be reached. B. may give more trouble with sticking choke since the internal fast idle piston is harnessed direct to the butter-fly, and it is worth while noting that Cadillac have this year given up the internal system in favour of the external system used by Buicks. The objections to the external system, however, are fundamental, whereas it should be possible to modify the more desirable internal system to work satisfactorily. Rm {William Robotham - Chief Engineer} /TAS. {T. Allan Swinden} | ||
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).