HEIGHT

    Styling of todays car has obviously become a very important factor and one of the trends is toward lower hood lines. Carburetor and air cleaner heights have been reduced year after year until it seems almost impossible to build them any lower. Since fuel injection does not require a down draft of air intake, it offers interesting possibilities in being able to reduce height for future styling requirements.

OTHER ADVANTAGES OF FUEL INJECTION

    Since fuel delivery does not depend on level of fuel in a bowl, operation of the fuel injection system is very little affected by maneuvers like tight turns and steep hill climbing.

    Since the fuel is sprayed into the warm part of the engine, much less extra fuel is required before the system is operating at normal performance.

    Response to the throttle is instantaneous since the fuel is under pressure at all times and needs only to be released for acceleration.

    Another possibility in fuel injection is that fuel, since it is supplied separately from the air, can be shut off completely during decceleration if desired. This could reduce the amount of unburned hydrocarbons exhausted to the air and could also offer some improvements in fuel economy.

TYPES OF FUEL INJECTION SYSTEMS

    Different fuel injection systems can be described in two ways - by where the fuel is injected and by whether it is timed or continuous in flow.

    One system which has been in use for many years is the timed direct cylinder injection such as used in a Diesel engine, where the nozzle is right in the combustion chamber and sprays fuel into the chamber when the piston reaches top dead center on compression. This system has been successfully used on Diesel engines but involves rather complicated and expensive timing devices and pump equipment.

    A second system is timed port injection which is currently offered by several manufacturers. The nozzle is located in the intake port and sprays fuel toward the intake valve whenever the valve is open. The timing equipment required is still rather expensive and there is some question as to whether the timing of the discharge has enough advantages to offset the additional cost.

 Continuous flow port injection has been used for some time as an accessory for racing application. Fuel is sprayed continuously into the intake port at such a rate that a full charge is delivered over a complete cycle of the engine. Since injection of this type involves a nozzle with no valve of any sort, vacuum effects on the fuel spray have been a problem. With pressure behind the nozzle and a variety of vacuum values ahead of the nozzle, it has been very difficult to control fuel flow, particularly at idle and low speeds.

    After testing all the current systems at this time, GM engineers concluded that continuous flow port injection was the most practical system for American automobiles, for no system on the market had been able to provide the necessary full range in performance. Therefore, the GM Technical Center Engineering staff set to work to design a new continuous flow fuel injection system.