An Interesting mom wit Fuel Economizer AIR VA LVE T HE modern
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carburetter has reached a high degree of efficiency in its adjustment of the supply of petrol to the engine when under load. On deceleration, •however, a high vacuum is created in the cylinders and inlet pipe by the pumping action of the engine, with the result that, in spite of the throttle being closed, an appreciable quantity of fuel is drawn into the engine. This fuel is not only wasted, but 'may be detrimental in causing dilution of the lubricating oil.
In order to prevent this wastage the Econom Syndicate, Ltd., 1, Broad Street Place, London, E.C.2, has placed upon the market a device the object of which is to relieve the vacuum in the inlet pipe when decelerating, by means of an automatically controlled valve which admits a quantity of clean air to the engine independently of the carburetter, • The automatic control is so arranged that this valve is closed at all times when the engine requires power, either idling or pulling, but instantly opens when the accelerator pedal is released and the engine functions as a brake.
The device is mounted either between the carburetter and the inlet pipe, or upon the inlet pipe itself. The valve is operated through the medium of an electro-magnet by a switch attached to the throttle-control lever, and, as will be seen from the accompanying illustration, a small relay coil fitted with a make-and-break switch is embodied.. The main coil, accelerator switch and relay switch are wired in series with the battery to earth, whilst the relay coil is on a separate circuit between the dynamo positive and earth. The air valve opens when the two switches are closed, and this condition can only be attained when the engine is overrunning at a speed sufficient to cause the dynamo to charge.
Three conditions of running must be provided for these being running under load, idling and starting up, and deceleration. It will be seen that when running under load the throttle is open and the dynamo charging; therefore, the accelerator switch is open and the air valve remains closed,. When idling and starting up, the throttle is closed and the dynamo is not charging; the relay switch is, therefore, open and the air valve remains closed, On deceleration and when over-running, however, the throttle is closed and the dynamo is charging; both the accelerator switch and the relay switch are, therefore, closed, and the air valve is opened by the energizing of the electro-magnet.
In the case of a vehicle fitted with a voltage-control regulator a separate relay is employed. The coil is placed in the dynamo field circuit, and in this case the relay switch remains open when the voltage output from the dynamo is below a predetermined limit.
Tests on various types of vehicle have shown fuel savings in the order of 10 to 20 per cent, to be obtainable, and it is noteworthy that a number of buses in the Paris fleet has been equipped with this device.