LPG/Diesel How does it work
High-pressure liquid petroleum gas (LPG) is converted to a low-pressure (just above atmospheric) useable gas. The gas passes through a solenoid valve (or stepper motor) which is controlled by outputs from the system’s computerised processor measuring precisely the quantity of gas required.
Computer Module for LPG
This metered amount of vapour travels through a hose into the
vehicle air intake system and subsequently into the inlet manifold
as a mixture of air and gas.
The computer module (processor) controls the flow of gas optimising
performance and ensuring safety. Manifold pressure (via a MAP
sensor) or throttle position (via a throttle position sensor) and
engine speed are monitored. The module then adjusts the gas flow
depending on engine load and driver demand.
The amount of gas injected (or the ‘gas map’) is completely (and
only) programmable by a laptop computer. This allows a large degree
of flexibility to adjust the system to suit your requirements.
The system does not allow LPG into the engine at idle and is
programmed to limit the amount of gas introduced at maximum load to
prevent over-fuelling. The system shuts off gas flow when the brakes
are applied or the driver’s foot comes off the accelerator.
The system can be switched on and off (if ever necessary) via a dash
mounted switch. If gas is unavailable or you run out before a
service station, it is not necessary to switch the system off.
Instead you will notice a decrease in performance as the gas runs
out. Since the diesel injection system is not modified, the vehicle
will simply run on diesel as it did prior to the system being
fitted.
LPG is Cost Effective
LPG for diesel is cost effective
As a result of the increased efficiency created by burning more of
the diesel injected into the combustion chamber, less diesel is now
required to travel each kilometre, therefore extending the range
travelled on each tank of diesel. Or, to look at it another way, the
same amount of diesel will deliver more power and torque.
Documented evidence indicates net fuel cost savings of 10-20% are
achievable running on either bio-diesel or normal diesel. A 4x4
vehicle will use approximately one litre of LPG for every 25-30
kilometres travelled under normal driving conditions. For further
explanation, see Economy section.
This Diesel/Gas system will increase power and torque by up to 20%
(sometimes more). This power increase is due not only to the
increased combustion efficiency, but also the LPG itself produces
power as it burns. So even the most economical gas map and driving
technique will produce some additional power. A more powerful
setting can still produce better economy than running on straight
diesel.
This extra power is instantly noticeable from the moment the system
is turned on. However, as the engine clears carbon deposits over
time it is not unusual for the advantages of the system to increase.
Image to the left is of a power run with the Patrol on the Dyno
The power and torque increase applies over the whole rev range.
Turbo lag is all but eliminated, and engine noise and vibration is
dramatically reduced all the way through to maximum revs. The driver
will notice fewer gear changes and higher average speeds,
particularly on hills and when towing.
LPG engine oil stays cleaner
For those of you with experience with LPG vehicles, you would know
the engine oil stays much cleaner between oil changes. LPG engines,
when stripped, are almost spotless internally. On the other hand
diesel engines are quite dirty internally and after an oil change
the new oil quickly becomes black again.
In a diesel engine this black stain is soot. Soot is the result of
incomplete combustion (the same as any wood fire stove). This soot
(which is actually carbon) gathers in the combustion chambers,
lining the top of the pistons, the injectors, the glow plugs and the
valves. Some stays there and builds up into thick carbon deposits
that must be scraped away when the engine is stripped. Some is blown
into the exhaust manifold, coating the inside of the exhaust pipe or
blown out the back as black smoke. The rest is washed off the
cylinder walls by the engine oil, thus contaminating it and turning
it black. This is why engine oil filtration is critical in diesels.
With enough carbon contamination, oil soon loses its ability to
lubricate (viscosity) and clean properly, leaving abrasive deposits
on critical components and allowing further carbon build-up. This
causes engine wear - hence the need to change the engine oil on a
regular basis. Anyone who changes their own oil will tell you that
with diesels the oil becomes very black, very quickly. This
indicates that the oil is doing its job but it is also already
breaking down and losing its effectiveness long before the next oil
change is due.
Since LPG is a clean burning gas it does not leave soot behind. This
is why the engine and oil stay cleaner for longer. With the
Diesel/Gas system cleanliness is achieved slightly differently. The
gas introduced acts as a catalyst encouraging a more complete diesel
combustion. This means less soot (a lot less soot) which, in turn,
means the oil stays cleaner. Now, if the oil is staying cleaner,
that means it is not carrying as much contamination, and is
therefore doing its job better and for longer. The upshot is reduced
engine wear between oil changes and over the life of the engine
(which is extended as a result).
Engine operating temperatures are not increased by running this
system. Exhaust gas temperatures are reduced, since there is no
longer fuel being burnt in the exhaust system.
