NEW PETROL SYSTEM

Manawatu Times, Volume LIV, Issue 6802, 4 January 1929, Page 5

NEW PETROL SYSTEM

CARBURETTER, AND REAR TANK COMBINED—VACUUM TANK DISCARDED. The ordinary carburetter works on a principle winch has remained practically unchanged for 25 years (says the ‘Motor’), and in order to get smooth running with multi-cylinder engines, it has been found necessary to apply considerable heat to the mixture of air and petrol particles which such a carburetter produces. This heating of the charge reduces its weight and therefore lessons the power output of the engine. Again a carburetter must be provided with a reservoir of petrol at a constant level—the float chamber — and complication is further increased when the fuel is carried in a rear tank owing to the necessity for providing an intermediate reservoir in the shape of a vacuum tank. f Clean Cut of Elaborations.

Latterlv, a step towards simplification Ims been taken by evolving simple forms of electrical and mechanical pumps for delivering petrol to the float chamber, but a new Stewart-Warner system makes a clean cut of all these elaborations, at the same time providing the cool mixture necessary for the best engine performance. The rear tank contains a vertical cylinder with a float at the bottom maintaining a constant level of fuel in just the same way as a carburetter float. An air pipe about iiin. in dia-

meter enters this cylinder, passing to the bottom and then spiralling upwards; at two points it is provided with venture passages and petdol jets. Engine suction, acting upon this lengthy pipe, draws the air through from the rear, and in passing the jets it picks up petrol to form a rich, wet mixture.

IVhen this mixture reaches the front end of the car it passes through an ex-haust-heated box (which ensures thorough vaporisation) and then enters a mixing chamber placed adjacent to the inlet, manifold. This chamber is subjected to engine suction and contains a spring-loaded air valve, so that under normal conditions of operation the engine draws in the rich hot mixture and cold air in tho proportions of about 1 to 4. A throttle of the ordinary kind is placed between the mixing chamber and the inlet manifold.

When starting from cob' a ciiuke can be- operated which shuts the air valve, so that the engine is supplied solely with the rich mixture, but after the first few explosions this choke can be released, as the heat of the exhaust bo* is: then sufficient to ensure vaporisation. Excellent acceleration is ensured by providing a slight lag in the action of the air valve, and also owing to the fact that a certain amount of fuel becomes deposited in the lengthy piping. In other words, when the throttle is opened suddenly the richness of the mixture is temporarily increased so as to give a rapid pick-up.

Reduced Eire Risks. Reduced fire risks are also claimed, as the mixture in the pipe is too rich to ignite readily, and tests have been carried out showing that severe backfiring cannot be made to cause flames. Tests have also shown that a higher power'output and lower fuel consumption result from changing over to this new system. It would appear that the only trouble which would be possible.on the road is the choking of the jets in the rear tank, and wc arc informed' that the design is such that these jets can readily be removed.

It should be explained that at normal and slow speeds the petrol is supplied to the air solely through the bottom jet. At high speeds, however, the increased suction produced in the upper venture passage causes petrol to bo sucked up through this jet also, so providing the necessary compensation to ensure a uniform mixture strength.

The air valve on the mixing chamber is balanced by means of a lever and dashpot operated on the air-bleed principle so as to provide the lagging action of tho valve during acceleration already mentioned.