Sequential Injection System - 

Specification Information

Engine

The engine conversion uses Sequential Gas Injection technology to inject vapor gas direct into the inlet manifold allowing the engine to run on Liquefied Petroleum Gas.

The basic engine components are as follows:

Regulator: This unit is mounted in the engine bay and allows the liquid gas coming from the tank under its own pressure to be vaporized by the means of water heating taken from the vehicles engine. During this process that gas changes from liquid to vapor and the pressure is reduced to around 1bar. The gas is then allowed out of the regulator to the gas injectors ready for use. The regulator also monitors water temperature to give a particular reference to change over time from petrol to gas in excess of thirty degrees. The regulator also incorporates safety features to include pressure relief as well as and electrovalve shutoff (incorporating liquid filter) ensuring that when the engine is not running that the gas supply is also stopped.

Manifold Absolute Pressure sensor: This unit is mounted in the engine bay and monitors the supply pressure of the vapor gas from the regulator to the injection rail as well as the inlet manifold vacuum of the engine. The unit’s primary function is to give an engine load reference for the SGI ECU to follow so the gas fuel mixture is corrected as well as monitoring gas pressure. The gas pressure monitored also acts as a signal to reduced pressure from the gas tank and running out of gas, this then triggers the SGI ECU to change the system back to petrol and give the driver warning through the cab mounted change over switch.

Injection rail: This is the injection rail that actually does the most work by injecting the gas into the engine. Specially adapted nozzles are drilled and tapped into the engine inlet manifold near to the existing petrol injectors. The electronic gas injector via hose is connected to this nozzle and is capable of delivering the gas to each engine cylinder on demand. Also fitted to the Injection rail is a gas temperature sensor, which constantly monitors the gas temperature during engine running sending the data back the SGI CPU.

Low pressure Gas filter: This unit is installed just before the injection rail on the main vapor feed line and is used to offer second form of filter protection before the gas reaches the injectors.

Sequential Gas Injection CPU. The brain of the system is linked via a specially designed engine bay wiring harness with connections to interrupt petrol signals, obtain engine speed reading and receive data from the various gas system sensors as previously described. The petrol injector signal is received through the ECU and with the cab mounted changeover switch in the petrol position it allows the signal to each of the petrol injectors allowing the engine to run on petrol. With the cab mounted changeover switch selected to LPG mode the petrol injector for each engine cylinder is cut off one at a time and replaced by a gas injector. This gives give the engine smooth transition between fuels unnoticed except via the change over switch LED lights. Signals derived from the existing petrol ECU are received by the gas ECU and injection time of the LPG fuel modified. This input of signal from the petrol ECU allows the gas system to run as a "slave" system copying exactly the various petrol functions such as traction control, cruise control, RPM Limit as well as On Board Diagnostics.

Change over switch: This unit can be mounted discreetly on the vehicle dashboard or lower under dash panel. The switch incorporates a small push button that allows the driver to select the fuel to run on either petrol or LPG; indication of this is given via Led on the changeover switch. The switch also incorporates a fuel gauge by indication by four green Led and one red Led the average content of the LPG tank. The switch also incorporates a small buzzer and if the vehicle is driven without been refueled with LPG the switch will automatically switch back to petrol (indicated by flashing gauge lights) and an audible buzzer will sound indicating to the driver.

Gas tank: Generally two types of steel tank are available, ring tank or toroidal versus conventional cylinder tank. Ring tanks are generally used in place of a spare wheel where the more conventional cylinder is used boot mounted or in some cases under-floor or chassis side. Each of the tanks carries the same range of safety valves housed inside a vapor proof valve box, which is vented to atmosphere.

The main valves are electric take off incorporating an excess flow this valve shuts off when the engine is not running sealing the gas flow from tank to engine.

Pressure relief valve ensures that in the event of an accident and possible fire situation that the tank pressure is controlled in a safe manner protecting the tank from any over pressure.

A float gauge is fitted to allow a reading to the Dashboard as to the fuel level inside the tank.

A Fill valve incorporating a check-lock allows fast fill with automatic one way protection and eighty- percent maximum fill controlled ensuring that the filling cycle is always quick and safe.

Tanks are generally mounted directly to the vehicle chassis but in the case of certain cylinder type fitment the tank may be strapped into a frame and the frame bolted to the vehicle chassis. Feeding the Liquid LPG forward from tank to regulator is done under the tanks own pressure (no pump required) and is fed under floor through a high-pressure plastic coated feed line clipped to the underside of the vehicle.

Filling point: This is located either on the vehicle panel or rear bumper skirt. The filler incorporates a one way valve and is the standard UK bayonet fitment. Alternative filler adapters are available that screw directly to this filler to be used in other visiting countries if required. The fill pipe to tank is a special made up LPG high pressure rubber hose and are pressure tested before use.