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The GasResearch Throttle Body System - How Does It Work?

The GasResearch throttle body system has been developed in Australia by GasResearch Pty. Ltd. to provide a high performance alternative to common fumigation type LPG systems.

The throttle body system incorporates a specially developed gas convertor, and gas throttle body (carburettor).

Suitable for EFI vehicles in dual fuel configuration, and for both EFI and carburetted vehicles in straight gas applications, the GasResearch system introduces a new level of performance and economy to LPG installations.

The secret to the success of the GasResearch system lies in its versatility.  Three separate fuel circuits, each individually tuneable, ensure that the desired fuel/air mixture can be obtained right across the engine’s operating range.  A narrow envelope and a bolt pattern matching many modern vehicles ensure that installation is an uncomplicated affair.  A wide range of adaptors and facilities for retaining features such as cruise control, idle air control, throttle position sensing, and closed loop control mean that there are few vehicles, old or new, that cannot be fitted with GasResearch products.

The following is a brief outline of the various features of the GasResearch throttle body system.

The Convertor:

The GasResearch B2 convertor turns the liquid LPG from the tank into a gas, and delivers it to the engine via the throttle body.

The GasResearch convertor has been specially developed to accurately deliver fuel based on the vacuum signal generated by the throttle body. This matching of throttle body signal pressure and fuel delivery pressure between the throttle body and convertor is key to the smooth performance of the system.

As the fuel delivery characteristics of the convertor are closely matched to that of the throttle body, other brand “off-the-shelf” convertors (including the LG B2 in standard form) will NOT work correctly with the GasResearch system.  These convertors lack some of the key features of the GasResearch convertor and typically require stronger signal pressures as generated by diaphragm mixers, meaning increased engine restriction and less power.

Other important features of the GasResearch convertor include improved sensitivity for better throttle response, and internal referencing of primary and secondary stages to eliminate lean outs under hard acceleration.

The Throttle Body:

The GasResearch throttle body consists a butterfly throttle valve, separate idle and progression circuits, and a main circuit controlled by a metering valve.  Adjustment screws along with restrictor jets and calibrated metering rods control fuel/air mixture. The position of the main metering valve is controlled via the throttle position.

In the idle condition, fuel and air is supplied to the engine via the idle circuit.  This circuit consists of an air bypass channel, and fuel supply pipe.

The air bypass channel consists two intersecting passages formed within the wall of the throttle body, connecting the air supply and vacuum sides of the throttle valve, with an adjustment screw limiting the passage of air through the circuit.

The fuel supply pipe connects the main vapour inlet of the throttle body to the air bypass passage, allowing fuel to flow from the convertor to the idle circuit.

Fuel and air is drawn through the idle circuit by the low air pressure condition in the inlet manifold.  Fine tuning of the idle mixture can be achieved by adjusting the idle screw in the idle circuit. Course adjustment is possible by inserting a jet into the fuel supply pipe, to restrict fuel flow to the circuit.

Idle speed adjustment can be achieved using the idle speed screw on the throttle plate.  The idle speed screw alters the stop position of the throttle valve, therefore allowing the throttle to remain slightly open at idle.  It is important that the idle mixture is adjusted before idle speed, as excessive throttle opening causes the manifold vacuum to be reduced, and also brings the progression circuit into play.

The progression circuit consists of a fuel supply pipe, and a slotted progression port.  The supply pipe provides fuel from the main inlet of the throttle body to the progression port. The progression port is slotted to enable the gradual exposure of the port to manifold vacuum as the throttle valve is opened.  The progression circuit is tuned by inserting a jet in the fuel supply pipe to restrict fuel delivery.

The progression circuit enables smooth progression between the idle circuit and main circuits, preventing lean-out backfires or flat spots. The progression circuit also influences part throttle operation such as under cruise conditions.

The main circuit consists a fuel metering valve with interchangeable metering rod, and venturi diffuser system for delivering fuel directly to the airstream at the throttle body.

The fuel metering valve is operated directly in conjunction with the throttle valve.  This enables the fuel to be metered into the engine in direct proportion to the throttle position and therefore driver demand.

The interchangeable metering rods are shaped to provide a variable orifice as the valve moves within the valve body.  The rods are calibrated in a range of sizes, and available in 2-step or 3-step configurations.  Each step along the rod length is progressively smaller, to allow more gas to flow as the valve opens.  Universal metering rods are available for users who wish to create their own profiles allowing infinite adjustment of fuel mixture in the main circuit.

The metering valve seat is spring loaded to allow the valve shaft to move through the initial period of movement without opening the valve and allowing gas to flow to the diffuser.  This is to allow the progression circuit to operate before the main circuit comes into action.

Timing of the main circuit in relation to the progression circuit is critical to ensuring the correct operation of the progression circuit. The position of the metering valve in relation to the throttle valve can be adjusted by loosening the throttle plate nut and rotating the drive gear.  The metering valve should start to open as the throttle butterfly approaches the end of the progression slot.  

The diffuser has been designed to use air passing through the throttle body to create a proportional negative pressure signal with minimal restriction to the engine inlet.  This negative pressure signal is used to the draw fuel from the GasResearch convertor, through the metering valve and into the engine airstream.

These two devices combine to provide fuel metering dependant on the throttle position and engine speed from part throttle openings to wide open throttle conditions via the main circuit.

What all this means is that with the unique way that the GasResearch system controls the fuel delivery to the engine, whilst providing minimum restriction to the air inlet, maximum performance and economy can be realised by your engine whilst running on gas.

Call us now on 1800 550 335, or contact one of our recommended installers to find out more.