Digital Gas Injection

Multipoint LPG injection for low exhaust - gas emissions. and optimum engine performance

Technical developments is advancing with increasing speed in the field of static ignition and multipoint-fuel systems for petrol engines.
The LPG in the current DGC autogass systems, is fed into the engine's intake system centrally (singlepoint).
In the future the singlepoint system will be increasingly difficult to apply within the concept of an engine developed for multipoint injection. In spite of the very good results being achieved with current DGC systems.

AG Autogas Systems has the solution:
DGI - Digital Gas Injection.

AG Autogas Systems has developed the DGI high-tech MULTIPOINT GASEOUS LPG injection system over a period of 6 years.
The LPG injection which injects the LPG in pulses independently timed for each cylinder, is a new feature of this innovative system.

Just as with a petrol injector, the quantity of LPG injected is regulated by varying the duration of opening. In the heart of the injector, a large plunger is drawn up electronically, after which an LPG pulse is injected.

The DGI computer receives information from an orifice meter which measures the volume of the LPG injected. Situated behind the orifice meter, a splitter divides the main pulse exactly into three or four equal parts.

The Closed-loop-flow feedback system compensates automatically and immediately for variations in LPG pre-pressure or injector behaviour so that this has no repercussions for the injection programming.

The DGI system can control 2 injector groups entirely independently - each group has its own index fields and lambda regulation so that the following combinations are possible:

• 4 cylinder engine: 1 group injector with 4-splitter

• 6 cylinder engine: 2 group injectors with 3-splitter

• 8 cylinder engine: 2 group injectors with 4-splitter

Zero-pressure regulator
The LPG pulse is injected at the engine's intake valves by means of small zero-pressure regulators . The regulators keep the pressure in the hose between injector and engine intake at constant atmospheric pressure and avoid cross-interference between cylinders through suction-strokes and pulses.
The zero-pressure regulators also feed the LPG pulse into the intake manifold.

DGI Vaporizer
A new DGI Vaporizer regulates the LPG feed for the injector. This 1 -step vaporizer is equipped with an integrated shut-off valve and vaporizes the liquid LPG from the tank to a regulated pre-pressure of 0.8 bar.
The MAP (manifold pressure) reference entry point is a new refinement, which causes the regulated LPG pressure to vary slightly with the engine vacuum (0.7 bar hen idling - 0.8 bar at full-load).

DGI computer
The advanced DGI management computer uses engine-speed and load sensor signals to calculate the basic quantity of LPG injected for each engine revolution. This quantity is corrected by lambda regulation, using the lambda signal in the exhaust pipe, and any variations are stored in a memory index field. During acceleration, extra fuel is injected for a short time at high frequency while during deceleration the LPG fuel supply is shut off. A unique feature is the electric drive for the LPG injectors which is completely flow-regulated and is thus independent of battery voltage and/or temperature variations. The closed-loop flow regulation for the injector uses the feedback flow-signal to control the duration of opening so that the correct amount of LPG is injected.

Diagnosis
For system control and diagnosis, the dealer can use the Organizer from the AG test kit to establish direct contact with the DGI computer.
All signals, self-learning data or error code data can thus be checked and read out.
After installation, the DGI system must be briefly programmed via this Organizer. In all cases, the R&D department can be requested to perform a remote diagnosis via a modem link and offer help where possible.

Advantages:

• DGI Multipoint LPG Injection greatly reduces the risk of backfire.

• The difference in engine power-output between LPG and the petrol original is almost zero, thanks to the absence of a venturi choke.

• Better fuel-economy through shutting off of LPG injection during deceleration.

• Exhaust emissions satisfy the stringent European demands and the Dutch G3 test.

• Because of the injector's high speed and wide opening, the DGI system is not prone to fouling. This guarantees optimum performance in summer and winter.

Development of the LPG market
In European, the requirements regarding exhaust emissions are being continuously tightened and this attention to the environment is leading governments to encourage driving on LPG. LPG is also receiving greater attention worldwide. A great many large cities are increasingly permitting access to LPG cars only in order to prevent smog.

The LPG market is clearly going to see further positive development in the coming years. The demand for LPG systems, satisfy the most stringent demands is keeping pace with this. In the Netherlands, considerable reduction in road-tax for cars equipped with the so-called `G3' autogas system, will increase drastically the demand for LPG systems.

The new G3 requirements
For AG Autogas Systems, investment in developing systems which satisfy the latest requirements was obvious from the very beginning. Having anticipated changed requirements, AG is now in a position to offer a fully operational DGI system which not only achieves emissions of at least 30% below the standard for petrol (in accordance with the new G3 requirements), but which also eliminates the difference in performance between petrol and LPG for the driver.
Digital Gas Injection is a self-learning, non-adjustable system providing optimum engine performance and low exhaust emissions and is developed by a company that satisfies the stringent ISO 9001 standards.
DGI satisfies all the G3 requirements which enable, in the Netherlands for instance, an immediate and considerable reduction in road-tax for driving on LPG after installation of the system.

On a worldwide scale AG Autogas Systems is one of the top autogas systems suppliers and has been active worldwide in the market for more than 25 years. This market has developed to a high level in the Netherlands and Italy in particular, and why AG is chiefly based in these countries. Close cooperation with a large number of car-manufacturers and importers means that the AG systems can be offered on a worldwide scale.
AG has worked to a clear philosophy regarding quality.The ISO 9001 certification.

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