Liquid injection technology is not altogether new. The theory or injecting high
pressure liquid LPG directly behind the intake valve has been widely accepted
as the most efficient method of fuel delivery on multi point petrol/lpg engines
even above vapour injection.
Since the early 1990’s an enormous amount of product development has taken place in
Europe, North America and Australia to bring to the market systems that can consistently prove emission control
durability, performance and economy.
On the first of July 2008 the JTG liquid injection system was released in Australia. With
around 80,000 systems sold both here and in Europe other products have been developed and introduced. In fact, liquid autogas
injection has been adopted by the Ford motor company and Holden Special Vehicles as a factory option.
What is the main difference or advantage of Liquid Injection over Vapour Injection?
- A vapour injection system injects the LPG vapour at around 30psi of pressure via a 4mm injector nozzle at 60 degrees Celsius.
- A liquid injection system injects the high pressure liquid LPG at 200 psi of pressure via a 1mm injector nozzle at 0 degrees Celsius and is aimed directly towards the intake valves.
Therefore as the higher pressure liquid LPG is injected at high velocity through a smaller discharge nozzle the rapid release of the freezing gas cools the air
intake charge behind the intake valve. This gives a more condensed oxygen laden air charge in the cylinder. (This is very desirable for performance.) “ A consistent controlled temperature drop.”This high velocity discharge also creates a negative pressure on the “Fresh air
side” also “drawing more air”
“This is the performance aspect”
Another benefit of liquid autogas injection system on a late model vehicle is that the
adaptive engine management systems including air temperature sensors and knock
sensors are intelligent and can detect the cold, high octane (105-110) autogas
above 91-98 octane petrol and adjust ignition timing to optimise economy.
There are two liquid autogas injection systems fitted by Smithy’s LPG and Automotive
Services Orbital and JTG.
What system do I want?
What system do I need?
What are the main differences and advantages of Orbital LPI or JTG?
orbital LPI systems as used by Ford for its Falcon range and by Holden Special
Vehicles are “fully fledged” and are absolutely model specific with little
deviation possible from the original design.
Orbital LPI systems fitted by Smithy’s use variable 5 speed high pressure
internal pumps in the model specific bracketed LPG Cylinder assemblies.
Tuning of the Orbital system is done in the same manner as a vapour injection system
by using an LPG ECU.
ECU uses the original petrol injection signal to trigger the LPG injectors and
then uses a manipulated injection signal to deliver the correct fuel quantity
for precise engine tuning.
ECU map is “Fixed and Locked” and cannot be altered. It will not support
after market flash tuning edits or increased turbo boost procedures.
Advantages of ORBITAL liquid injection
The Orbital system is of the highest standard of quality and very suitable for all standard production vehicles giving around a 5% increase in mid range performance above petrol.
Orbital system is very cost competitive, even compared with vapour injection.
Orbital system does revert back to petrol under heavy load.
Although using a “similar” principle of operation of injecting the LPG into the intake
manifold the JTG systems’ execution and implementation differs greatly from the
Orbital system. The JTG liquid injection system uses a single speed high volume
pump with an external pressure regulator on the return line to the LPG
The LPG pump and entire system are capable of supplying even the strongest engines
to full power under wide open throttle without any pressure loss and without having
to revert back to petrol because of inadequate LPG pressure and volume
The advantages of this are obvious:
- The engine will not revert back to petrol unnecessarily diminishing the saving of LPG.
- The engine will continue to have the thermal advantage provided by liquid injection at full power enabling the engine not only to have 5-10% more midrange torque than petrol but also develop up to 10% more horsepower than petrol.
The fuel calibration of the JTG system is unique.
How is this done?
- It does not use an ECU
- It does not manipulate injection signals
- It uses “Real” petrol injection timing.
- It can support flash tunes, edits, engine modifications and increased boost pressure.
The JTG system does not revert back to petrol under heavy load and will support the
engine to full power and beyond:
- Flow rated suitable injectors
- Adjustable fuel pressure regulator
- Calibration of injectors via “fixed hard calibrators”
The JTG system is not only suitable for all standard production vehicles but also
most modified vehicles.
The system itself is highly adaptable to a variety of applications including
vehicles that do not have an Orbital LPI system available:
LPG and Automotive Services can even “create” a system suitable to a specific
early, custom or modified vehicle.
What is the main benefit or advantage of the JTG system over the Orbital LPI system?
- Greater midrange performance from higher discharge pressure directing fuel to the intake valve pocket.
- Greater power than petrol under wide open throttle.
- Can support vehicle management and engine modifications
- Wider range of vehicle applications available.