The GasResearch Throttle Body System - How Does It Work?
GasResearch throttle body system has been developed in Australia by GasResearch
Pty. Ltd. to provide a high performance alternative to common fumigation type
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.
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.
following is a brief outline of the various features of the GasResearch
throttle body system.
GasResearch B2 convertor turns the liquid LPG from the tank into a gas, and
delivers it to the engine via the throttle body.
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:
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.