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).
Article on an automatic ignition advance device based on engine suction, reprinted from 'The Motor' magazine.
| Identifier | ExFiles\Box 163\7\ img165 | |
| Date | 9th December 1930 | |
| Reprinted from “The Motor,” December 9, 1930. Ignition Advanced by Engine Suction Entirely Automatic Device Which Gives Accurate Control Depending Upon Engine Load; Very Sweet Running and Improved Performance Obtained ALTHOUGH there have been great improvements in various components producing the car as we know it to-day, little alteration has been effected in the method of control of the ignition firing point; with the exception of the use of the centrifugal governor which operates solely in relation to engine speed, ignition control has remained in much the same position as that used on early cars, there being no provision for the alteration of the firing point dependent upon the load. Sectional view of the Delco - Remy automatic suction - operated ignition control. CONNECTION WITH INDUCTION MANIFOLD RUBBER BELLOWS RETURN SPRING Effect Upon Performance. It has for a long time been known that a certain maximum ignition advance can, and should, be given to an engine dependent upon the conditions of the load under which it is operating, and if such provision can be made to accommodate these fluctuations, a higher maximum speed, improved acceleration and greater smoothness of running, combined with reduced petrol consumption, should be obtained. After many years of research, Delco-Remy and Hyatt, Ltd., the well-known electrical engineers, of Grosvenor Road, London, S.W.1, have produced such a control, covered by basic patents and patents pending, having the advantage that it will be applicable to practically any car of popular make. The device is simple in construction, consisting of a rubber bellows barely larger than an ordinary matchbox, and having within it a coil spring which normally maintains the bellows in an extended position. Both ends of the bellows are sealed by caps, one being secured to a convenient fixed part of the engine and serving to carry a pipe connecting the interior of the bellows to the induction pipe; the other, which is free to move endwise within predetermined limits, connects to one end of a small compensating bar pivoted at its centre on the distributor timing lever. The other end of the bar is linked up with the normal hand-operated ignition control, which is retained for use if desired. Naturally, as the carburetter throttle position is varied by the driver in accordance with the load about to be placed on the engine, there is a variation in induction manifold depression, and this is consequently communicated to the bellows which are continually contracted and expanded in strict accordance with the load under which the engine is operating at any given moment. So far the operation is simple, but to ensure the maintenance throughout the entire engine speed range of the ideal firing point in relation to the load, great care must be exercised in arranging the linkage and in the location of the bellows connecting pipe where it enters the carburetter. Therefore the work of fitting the device will be carried out by the Delco-Remy service depots, of which there are many throughout the country. How the Suction Varies. The degree of vacuum existing in the induction system when the engine is running against more or less shut throttle conditions is high, but it becomes low when the throttle is opened, particularly when the engine is pulling hard up an incline and when the car is accelerating rapidly. The effects of these variations in manifold depression are well known to drivers of cars fitted with suction-operated windscreen wipers. When accelerating or in opening the throttle sharply the wiper will cease to function altogether for a while until the suction increases. With these points in mind it is easy to imagine how this variation can be applied to the control of the ignition, which, to provide sweet running and best performance, must be advanced and retarded with variations of engine load in addition to being timed in accordance with engine speed. This dual effect is obtained by using the Delco device just described in conjunction with the usual automatic governor control. We had an opportunity recently of driving a car thus equipped and were very impressed with the sweetness of running and the extraordinary way in which the engine would throttle down to an idling speed, yet propel the car without the slightest sign of snatch. The speed was less than 3 m.p.h.; the passenger stepped out of the car and was able easily to walk faster than the speed at which the car was travelling. Yet in response to the depression of the accelerator pedal the car pulled away sweetly and rapidly with no roughness at all, purely owing to the fact that the ignition advance was controlled entirely in proportion to the engine load. To obtain a comparison the automatic control was cut out and the hand system used. In this circumstance it was not possible to reproduce the same smooth running. How the control is fitted; (inset) the toggle bar, by means of which hand and automatic controls are available. This sketch gives an excellent impression of the compactness. TO HAND CONTROL TOGGLE AUTOMATIC IGNITION CONTROL No Loss of Speed. There is no reduction in the maximum speed which can be obtained after fitting the automatic control; further, to indicate how well the running it should be mentioned that the particular car tested had already covered over 12,000 miles without decarbonizing, and the running was such that one would not have imagined any heavy carbon deposit to be existent. The manufacturers have made very many tests of this device, and it has been found that a great improvement in fuel economy is produced simply by this automatic control of the ignition. The price at which it will sell is low, and further details are available from Delco-Remy and Hyatt, Ltd. DELCO-REMY & HYATT, LTD., 111, Grosvenor Road - London, S.W.1. | ||