Low Pressure Electronic Fuel Injection System for Two-Stroke Engines

Abstract

A brief general survey of different fuel injection systems is presented, and a new low-pressure fuel electronic injection system is described that is specially adapted to two-stroke engines. Due to its design, the two-stroke internal combustion engine has an important drawback, i.e. burnt gases during scavenging are thrown away by partly diluted fresh gases. It would be more convenient to carry out scavenging with fresh gases rather than with an air-fuel mixture in the crankcase, and this can only be achieved by a direct fuel injection quantity to avoid mixture of fresh gases and fuel particles. Due to recent trends toward fuel economy and pollution control, the future of the two-stroke engine may be jeopardized despite its positive advantages of robustness, simplicity, low manufacturing costs, and high power-to-weight ratio. The best solution to maintain requirements of the modern two-stroke engine involves electronic direct fuel injection. By adopting the capacitive discharge system, energy can be stored slowly for discharging in a very short time. To adapt a low-pressure injection system to the two-stroke engine encompasses some seemingly incompatible requirements: the system must be independent and not require an external energy source; injected quantities, though small, must be injected accurately and in a short period of time; and the system must be reliable without time draft. General aspects of the low-pressure electronic fuel injection system are described (air-fuel supply, injection time, spraying and distribution of fuel, and fouling and endurance). The principle of supercharged injection, the electronic control unit, and engine adjustments are detailed. Two main advantages of the system are fuel economy and pollution control.