Alternative Fuel 4x4

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. 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. Diesel/lpg Nissan

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 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.