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Basic installation and adjustment guidelines for autogas systems, part II

02.06.2017

The installation of autogas systems seems to be very easy at first sight. Maybe this is true, but errors are often made that are only noticed during the use of the vehicle. In the previous articles, I discussed operations that must be performed before the installation proper: how to select components for a given car, why it is worth to filling in the acceptance report to avoid future misunderstandings and how the problems in engines designated for autogas conversion can be identified. In this issue I will briefly describe the individual elements of the autogas system and the basic principles for its correct installation.

It is good to plan the installation of components well before starting the work. Choose the place and method for the installation of the reducer, the location of gas injectors and the routing of electrical wires to arrange the new system in an ordered way. It is also important that the new components do not block access to other parts of the vehicle, e.g. lamp bulbs.

The purpose of the reducer is to change the liquid phase of gas into vapor (volatile phase) and to maintain a constant pressure in the intake system to the injection rail. For the system to operate correctly, heating is required to expand the gas flowing from the tank. In reducers used in sequential systems, the vacuum pressure at the intake manifold is also important, as it is used to control the pressure regulator placed inside the reducer.

Reducer AC STAG

The location of the reducer in some cars is a big challenge for the fitter. Limited space under the bonnet, particularly in new models of cars, causes a headache. The basic rule is to mount the reducer on the fixed and rigid parts of the bodywork, using special fixtures. During installation, care should be taken that the reducer is not positioned above the cooling fluid tank, as this can hamper the correct circulation of the liquid through the reducer. Prior to selecting the location for the reducer, identify a good point for connection to the antifreeze line used for heating the reducer. Extended liquid circulation will slow down the heating of the reducer, which will cause a in the switch from petrol to gas. In some vehicles, the flow of the antifreeze through the engine should be analyzed in detail. If the car manufacturer used flow control valves, these can make the connection more difficult. The best position to divert the heating to the reducer is a point between the engine block and the heater – a serial connection is also recommended. In some cars there is a valve on the way between the heater and the engine. In such a case, connect the reducer before the valve, on the engine side. When connecting to the antifreeze lines, it is better to use metal tees. Using plastic tees may result in their deformation or breaking due to temperature variations.

engine photo STAG AC

Injection nozzles and vacuum nozzle

Making holes and the installation of the injection nozzles in the manifold is one of the most important operations during system mounting. Placing the nozzles in an incorrect location will result in engine problems when fueling with gas, e.g. rpm haunting when the gears are in neutral. Certain engines require a high precision of drilling and nozzle positioning.

Engine STAG AC Before drilling is started the intake manifold should be dismounted, especially if it is made of metal. During drilling, a large amount of shavings may get inside, which may result in engine damage. In some engines, precise hole drilling in the intake manifold is very difficult. Correctly mounted nozzles should be positioned as close to the petrol injectors as possible and they should be inclined at the same angle. Of course, remember that the positions of all the installed nozzles should be identical. Seal the threaded nozzle-manifold connection with a special thread locker resistant to high temperatures. Put hoses on the nozzles (recommended diameter - 4-5 mm) and tighten them with clamps. Remember that the length of all the hoses must be the same and as short as possible.

Another operation that interferes with the intake manifold involves making a hole for the nozzle to be located at a point where the manifold is not split, e.g. after the throttle. The hose inserted on this connector serves two functions: to provide information about the pressure inside the intake manifold and supply a vacuum to the reducer for membrane control.

Gas injectors

Gas injectors in systems of the 4th generation and newer deliver a gas dosage to the intake manifold. They are controlled by the gas controller, which generates the impulses to open the injector. The correct installation of gas injectors means that they last longer. If the injection nozzles are positioned upwards, they may become blocked. Contamination which passes through the filter is accumulated in the injectors. Each injector must have its nozzle positioned downwards or at an angle (observe the angle of petrol injectors). An operating engine generates some vibrations; therefore the injector should be attached to fixed elements of the engine with rigid fixtures, such as mounting plates.

engine with stag

Solenoid valve

engine with stagThe purpose of the solenoid valve is to open and close the supply of gas to the reducer. Most of the solenoid valves available on the market also act as the filter for the liquid phase. Its installation is quite important, as it catches most of the solid contamination of gas. Otherwise, this contamination would reach the reducer, which would reduce its life. The solenoid valve should be installed in an accessible place, due to the regular changes of filters which are required.

Volatile phase filter

filtr_stagThe next filter in the gas system is the volatile phase filter. This filter is mounted between the reducer and gas injectors. Its main task is to finally clean the gas of oily contamination. Thanks to this, clean gas is supplied to the injectors which feed it to the intake manifold.

Tank and multivalve

Tank and multivalveThe tank is used for the storage of gas. It is filled with gas in the liquid phase under approx. 7 bars. Autogas systems are provided with toroidal or cylindrical tanks. Both types must ensure stability by being fixed to metal parts of the vehicle. They must not move during driving. Toroidal tanks are installed in the spare tire well (laid in the cavity or hanged), while cylindrical tanks are fixed on a special rack in the luggage compartment. Every tank which has been installed should have a ventilation channel that is directed out of the vehicle to remove gas when a leakage occurs or the safety valve is activated.

Each tank is equipped with a multivalve placed in a special cavity cut in the tank. The multivalve allows gas to be taken from the tank to the reducer and the tank to be filled from the dispenser pump. While the tank is being filled with gas, the multivalve controls allow the tank up to fille to 80% of its capacity. Multivalves are also provided with integrated safety valves, which are activated upon excessive pressure inside the tank. With a float fixed to the multivalve, it is possible to measure the level of gas in the tank using an electromagnetic sensor.
to be continued...

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