The principle of using LPG as an alternative fuel to drive passenger cars is quite simple. Gas is supplied from LPG gas station to the tank through a filling connection, fitted on external side of vehicle body, using a gas distribution system. For this purpose are used high-pressure homologated hoses or solid piping of copper or steel.
The tank in a car may be filled to max. 80% of its capacity. The tank is equipped with a multivalve, which is under a hermetically sealed cover. The parts of the multivalve are filling unit, level gauge, overfill limiter, bleed valve, operating valve, (safety valve), flow fuse. The multivalve is equipped with a gas-tight cover so that eventually leaked gas cannot permeate into the car. There is a ventilation piping ran under the car.
From the tank the liquid phase of LPG is conducted by piping through a solenoid valve to a regulator - mixer. Here it comes in two stages to its vaporization (heating) and to its subsequent adjustment to an operating value of ca 3 kPa. Energy needed for liquid gas vaporization is supplied by hot water that comes from the cooling system of the motor.
In vehicles with injection system and controlled catalytic converter are used electronically controlled regulators with an assessment control unit and an exhaust gas oxygen sensor. Richness of the mixture influences the course of a working cycle of the motor and it is indicated by a coefficient of excess of air. Antiknock resistance and mixture heating value associate with it, as well as the height of a combustible temperature of the mixture. Richness of the mixture then significantly influences the composition of exhaust fumes and a rate of their harmfulness. For example, poor fuel mixtures have significantly lower concentration of nitrogen oxides (Nox).
Therefore, at these vehicles a great emphasis is put on the right timing of the mixture because otherwise the whole electronic system can be damaged. Nowadays are applied systems where fuel is injected to all cylinders directly. The entire system must be equipped with a quality catalytic system ensuring sufficient liquidation of pollutants.