4th generation equipment is commonly called a "gas injector" because it uses distributed injection, just like gasoline engines. Uninterrupted operation of modern systems is ensured by electronic control and precise calibration. That is why installing such a kit, as well as its price, is more expensive than equipping previous versions.
Control electronics
Each 4th generation system is equipped with an electronic control unit (ECU), commonly referred to as the "brains." This unit is responsible for the functioning of all gas equipment components, monitors the propane level in the cylinder, and the temperature in the reducer-evaporator. Simultaneously, the ECU "deceives" the vehicle's stock onboard computer, hiding the presence of the gas system from it. When the engine switches to gas, the unit intercepts signals from sensors, processes them, and sends corrected data to the onboard computer.
Gas supply is regulated by correcting the parameters of the gasoline system. During tuning, a specialist creates a fuel map, where every 500 rpm a correction factor is set for the opening time of the gas injectors. The basis is the opening duration of the gasoline injectors.
Thanks to this approach, manufacturers have managed to avoid expensive software development for each specific car model. Most ECUs have universal firmware for gas injection, and all refinements are made manually by the tuner through the controller interface.
The exception is engines with direct injection. For them, a scheme is used in which propane and gasoline are supplied simultaneously. The reason is that disabling the stock gasoline injectors reduces their service life. Therefore, for owners of such cars, installation is significantly more expensive, and the savings from using gas become less noticeable.
The path of propane from the cylinder to the cylinders
After turning the ignition key, the valve on the cylinder opens, and propane-butane flows to the reducer, but gas does not yet go to the cylinders. Starting a cold engine and warming it up are done on gasoline. This is a mandatory condition: you must wait until the coolant temperature rises above 40°C. This is necessary to compensate for the cooling of the gas that occurs when pressure drops.
When the antifreeze warms up to the required level, the car is ready to run on gas. The driver does not need to monitor the temperature — in 4th generation systems, switching is performed automatically, and the ECU is responsible for this. On the unit's command, the gasoline injectors are turned off, and the stock computer continues to receive signals from the ECU as if the injectors were working as before. Otherwise, the "check engine" light would come on and the car would go into emergency mode.
Instead of gasoline injectors, gas injectors start working — the engine receives vaporized propane-butane. Due to differences in fuel properties, the engine requires a larger volume of gas, so its consumption always exceeds gasoline by 10–15%, and trying to equalize these indicators is pointless. If the gas runs out, the ECU instantly switches the fuel supply to gasoline and blocks the gas line. Such automation allows the driver not to have special skills for driving a car on gas — it is enough just to fill the cylinder in time.
