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Government LPG conversion grant benefits round Australia retirees

September 09, 2006
Government LPG conversion grant benefits round Australia retirees

Retirees, the predominant round-Australia travellers who set off each year in a myriad of different types of recreational vehicles are among the big winners from the Governments LPG conversion grant, according to the Recreational Vehicle Manufacturers Association of Australia.

RVMAA President Tony Bellamy said that while the cost of fuel was but just one element of the round Australia trek budget, continuing increases in petrol prices were beginning to challenge the great Australian travel dream.

Now there is a great option available, so the trips can go ahead. By the time they get around Australia, the cost difference between the Governments grant and the price they paid for the conversion will have been paid off and more, Mr Bellamy said.

With the modern LPG conversion technology and the smooth-burning nature of LPG, there is often no perceived reduction in the power of a towing vehicle, and late-model campervans and motorhomes converted to gas can often retain comparable torque, Mr Bellamy said.

Another piece of good news from the RVMAA is that most conversions leave the vehicle with a dual-fuel capacity, so even in the remotest places, in the unlikely event that there is no LPG available; travellers can switch over to petrol.

However we are delighted that Ford has embarked on its round-Australia venture to prove that LPG is freely available in almost every place you would want to visit, Mr Bellamy said.

The RVMAA has in recent years become an advocate for LPG citing the many major financial, environmental, security and technical benefits over petrol and diesel.

Most motorists are unaware of the superior properties of LPG, or have been put off the fuel because of tales of poor conversions, Mr Bellamy said. However, there are now highly skilled people working in the business who do an excellent job. The best advice is dont always look for the cheapest, and do a reference check. Reliable conversion companies will gladly offer clients as referees, he said.

According to the RVMAAs executive officer, Colin Young, a quality LPG conversion on a typical vehicle with a moderate fuel consumption rate, costs around $2,500. With the Government subsidy the pay-back is just a matter of months to a vehicle owner travelling 16,000 km a year thats the kind of distance it takes to tour around Australia. Once the conversion is paid for, you continue to pocket the significant savings, and the re-sale value of your vehicle will have increased appreciably!

The built-in insurance is gas prices wont end up competing with petrol or diesel in Australia, as it has a large supply of home grown product, explained Mr Young, who is a highly experienced consulting engineer, with an American automotive engineering degree, obtained while at General Motors Technical Centre in Michigan. He is an A-grade mechanic with LPG and RWC licences.

For years commercial operators have reaped the benefit of LPG including taxis and delivery vans, Mr Young said. He stressed that from a towing performance perspective; vehicles operating on LPG can have engines operating at higher compression ratios or can allow for mild turbo-charging which means more power and better fuel economy for the same fuel flow without major engine modifications.


The main advantages of LPG are:

Abundant local supplies vast reserves, without relying on imports Cheap a small fraction of the cost of petrol and diesel Readily available excellent infra-structure that continues to expand to remote areas.

Conversion cost. The Federal Government grant turned this around to apositive.Conversions add to the re-sale value of vehicles.

Safe Extremely strong storage tanks

Gaseous fuel disperses and diffuses quickly

Higher ignition temperature 470 0C compared with 300 400 0C for petrol

Higher lower-flammability-limit 1.9% volume in air, compared with 0.6% for petrol

Non-toxic (anaesthetic only)

Clean-burning Much less CO (carbon monoxide) harmful emissions -

Much less HC (hydrocarbon) harmful emissions -

Much less NOx (oxides of nitrogen) harmful emissions -

No fine particulates (dangerous respiratory) emissions -

Much less emissions during cold starts no choke (enrichment) required

Simple fuel molecules - less Greenhouse Gas emissions carbon dioxide

The few hydrocarbons formed are not radical do not form smog

Power/economy-robbing emission controls often not required

High octane rating Prevents detonation stops pinging or knocking

Permits higher compression ratios more power for the same fuel flow

Permits turbo-charging more power, without engine modifications

Slow-burning smoother power and quieter combustion less NOx

Gaseous fuel does not wash lubricating oil off the cylinder bores much less wear

Does not get trapped in piston rings to form high hydrocarbons

Does not dilute the lubricating oil

Does not form carbon no abrasive carbon in lubricating oil

Does not form smoke even if the mixture is very rich

Cannot foul spark-plugs vital for emergency-service vehicles

No fuel line freeze-up in cold weather no water in fuel system

Mixes evenly and quickly with the induction air even air/fuel ratios

More tolerant to very lean mixtures will not melt pistons

No losses No evaporative losses completely sealed system

No pilferage

May add to the resale value of the vehicle

Less maintenance longer oil and filter life

Longer engine life no abrasives in oil, no dilution of oil

Longer spark-plug life no fouling

Simple fuel system reliable and very easy to diagnose and service

Less break-downs due to engine problems

Cost recovery of a conversion

Boats, caravans, motorhomes, cabins and tents at Lake Hume Tourist Park, GoSeeAustralia pic.
Boats, caravans, motorhomes, cabins and tents at Lake Hume Tourist Park, GoSeeAustralia pic.

Depends on the: Conversion cost, a vehicles fuel economy, annual kilometres, and the difference in the cost of petrol and LPG. Years = Conversion cost divided by fuel cost saving per year.

The LPG Australia web-site

Has a calculator to determine your annual fuel cost saving. From this you can quickly calculate how long it will take to recoup the conversion cost.

Once the conversion is paid for, you continue to pocket the significant savings, and the re-sale value of your vehicle will have increased appreciably!

Example: Conversion cost: $500 Travel: 16,000 km (10,000 miles) per year

Fuel economy: 17.7 litres/100km Petrol: $1.30 per litre LPG: $0.50 per litre

Petrol used: 2,832 litres per year Petrol cost: $3,682 per year

LPG used: 3,115 litres per year LPG cost: $1,558 per year

(Typically because of the lower energy content, consumption increases by typically 10%)

Fuel cost saving: $2,124 per year

Time to recover cost = $500 divided by $2,124, which equals just 0.24 years (2.8 months)!!!

Example: Conversion cost: $500 Travel: 16,000 km (10,000 miles) per year

Fuel economy: 17.7 litres/100km Petrol: $1.40 per litre LPG: $0.50 per litre

Petrol used: 2,832 litres per year Petrol cost: $3,965 per year

LPG used: 3,115 litres per year LPG cost: $1,558 per year

(Typically because of the lower energy content, consumption increases by typically 10%)

Fuel cost saving: $2,407 per year

Time to recover cost = $500 divided by $2,407, which equals just 0.21 years (2.5 months)!!!

Example: Conversion cost: $500 Travel: 16,000 km (10,000 miles) per year

Fuel economy: 17.7 litres/100km Petrol: $1.50 per litre LPG: $0.50 per litre

Petrol used: 2,832 litres per year Petrol cost: $4,248 per year

LPG used: 3,115 litres per year LPG cost: $1,558 per year

(Typically because of the lower energy content, consumption increases by typically 10%)

Fuel cost saving: $2,690 per year

Time to recover cost = $500 divided by $2,690, which equals just 0.18 years (2.2 months)!!!

Disadvantages of LPG for vehicles

Lower energy density there is a slightly reduced driving range for the same size fuel storage tank. There is simply not as much energy in a bucket of LPG as in a bucket of petrol. (Likewise, a bucket of petrol does not have the same energy as a bucket of diesel.)

Increased weight, due to the extra fuel tank; however, LPG (stored as a liquid) is lighter than petrol.

When to convert an engine to run on LPG

All LPG conversions must comply with Australian Standard AS 1425 - your assurance of a safe and professional conversion.

Coromal Silhouette 390, courtesy Coromal
Coromal Silhouette 390, courtesy Coromal

It also makes sense when an engine is old and worn and needs re-conditioning. When pistons, rings and valves need replacing anyway, and cylinder bores and valve guides need re-machining, you can achieve further performance, fuel economy and durability improvements by optimising the engine for gas.

The compression ratio can be increased slightly. Bore honing patterns can be altered, as can valve seat angles; valve rotators can be removed. You gain LPG benefits of not washing oil off the bores, and not forming carbon deposits. It is important the water passages in the block and head are properly cleaned to avoid over-heating. Needless to say, ensure the workshop re-conditioning your engine is experienced with LPG engines and has modern accurate machining equipment.


LPG Engines

LPG is an excellent fuel for:

Petrol (spark-ignition) engines, and

Diesel (compression-ignition) engines.

For spark-ignition engines, LPG can be used:

Single-fuel, or

Bi-fuel, where LPG is used as the main fuel, but petrol is used as a

limp home back-up fuel, or to extend the driving range; in this

case, only one fuel is used at any time.

For compression-ignition engines, LPG can be used:

Converting the engine to spark-ignition, using LPG as the only fuel, or

Dual-fuel operation, where diesel and LPG are used concurrently, that is, diesel is

used to commence the combustion, and LPG is induced into the induction

air to supplement the fuel supply to the engine.

For compression-ignition dual-fuel engines, two alternatives are available:

Leave the diesel fuel system completely standard, and simply add a small amount of LPG - typically around 15% of the total fuel flow - to the induction air. This is an easy but important environmental and good citizen first-step introduction to alternative fuels, and provides a modest power increase and fuel cost saving, and appreciably reduces the:

  • smoke,
  • smell,
  • noise, or

De-rate the fuel delivery system, and add a much larger amount of LPG - typically up to around 70% - to the induction air. This also increases the engine power, and provides a substantial reduction in fuel costs.

Note: The true meanings of bi-fuel and dual-fuel. Originally, and in many overseas countries, the above meanings were, and are, reversed. Dual-fuel LPG/petrol systems are, by the new definition, actually bi-fuel systems, where only one fuel is used at any time.

Spark-ignition Engines:

Preferably, LPG is used as a single-fuel, where the compression ratio and ignition timing can be optimised to provide the best possible performance power and economy while ensuring that the engine will maintain excellent reliability and durability. Petrol can be used as a back-up fuel, but it is vital that the ignition timing will not cause engine damage when running on petrol; dual-curve ignition units are available to safely allow petrol to be used as a limp-home fuel. Electronic dual curve ignition timing systems are available to provide optimum performance.

While propane can usually tolerate a compression-ratio of around 11 or 12:1 depending on the design of the combustion chamber petrol engines will only withstand a compression-ratio of typically 9 or 10:1 before the cylinder head gaskets fail. Unless a specific engine has sufficient metal to permit the use of metal sealing rings around the bores, it is not wise to increase the compression-ratio significantly when a petrol engine is adapted to LPG use.

Compression-ignition Engines

Converting to a spark-ignition engine requires injectors to be replaced by spark-plugs, the injector pump to be replaced by a distributor, and the compression-ratio to be lowered. Some diesel engines lend themselves better to this conversion than others; lower-compression, higher-revving engines provide the best efficiencies. Diesel engines are over-engineered for spark-ignition applications, giving exceptional reliability and durability.

The compression-ratio can be lowered by either using thick cylinder-head gaskets, or by machining metal from the combustion chambers in the cylinder head, or from the top of the pistons; this latter method can improve the engine power and economy by providing a better shape of combustion chamber. In some engines, it may be desirable to re-grind the camshaft to provide an improved valve-timing pattern to best suit the particular engine and driving usage characteristics.

Adapting a dual-fuel system does not alter the basic diesel fuel system. There are no spark-plugs, and diesel is still always used to start the fire, and keep the engine idling. However, as the engine speed increases above idle (as the driver depresses the accelerator), the control system: (a) Reduces or limits the amount of diesel injected into the engine, and

(b) Progressively increases the amount of LPG induced into the engine.

LPG is introduced into the inlet manifold at a slight positive pressure. Some dual-fuel systems employ a throttle in the inlet manifold as part of the fuel metering control system. As the percentage of LPG increases, and the percentage of diesel correspondingly decreases, the fuel cost savings along with the engine power increases.

However, the critical consideration, in terms of engine reliability, is how much fuel substitution can be safely tolerated before detonation and over-heating occurs. This percentage depends very much on the particular engine design, and the type of engine operation. Stationary constant-load, constant-speed engines (generators, pumps, etc.) can typically tolerate a 95% substitution rate, that is, at any time, the engine is concurrently using 5% diesel and 95% LPG. Road vehicles, with their continually changing engine speed and loading, usually are limited to a 70 75% substitution rate; however, this still provides exceptional financial and technical advantages.

What is LPG?

LPG, which consists primarily of propane and butane, is a simple fuel in the hydro-carbon family, and as such, has many significant advantages over other fuels, especially petrol blends which are a long way down the family tree, and have highly complex chemicals in them. A major advantage of propane - which has the formula of C3H8, meaning that each molecule consists of just 3 carbon atoms and 8 hydrogen atoms - is that it forms very few harmful pollutants. In fact, hydrocarbon emissions from a gas powered engine are not radical... in other words, they do not react with sun-light and oxides of nitrogen to form photo-chemical smog.

Ready for the Outback, GoSeeAustralia pic
Ready for the Outback, GoSeeAustralia pic


Chemical Name


Boiling Point 0C




Natural Gas





50.0 MJ/kg


Natural Gas













1.5 0.5







2.1 0.6


Hexane, etc.

(2n + 2)..

25 215

91 - 96




180 360




Bitumen, etc.

Stoichiometric: Methane 10:1 Ethane 15:1 Propane 24:1 Butane 32:1

% by weight: Methane 75 C; 25 H Propane 82 C; 18 H Petrol 86 C; 14 H Diesel 87 C; 13 H

C3H8 + 5O2 = 4H2O + 3CO2 C5H12 + 8O2 = 6H2O + 5CO2

2C5H12 + 15O2 = 20H2O + 4CO2 + 4HC + 2CO

LPG is stored as a liquid (at a moderate pressure, depending on the ambient temperature), but enters the engine as a gas. This gives the best of both worlds; a long driving range is achieved, and combustion efficiency (good fuel/air mixing and clean-burning) is significantly improved.

LPG has a very high ignition temperature, adding even more safety benefits in an accident. There is a downside to the overall benefits. In this case it means that a much hotter (higher energy) spark is required in the combustion chamber to ensure it ignites every time you want it to!

LPG is technically a superb automotive fuel, from a combustion point of view... it has a very high octane number (up to 110 RON), and fairly low susceptibility to pre-ignition. This means that the fuel can withstand a much higher compression pressure, without detonating. By increasing the compression ratio, or turbo/super-charging the engine generates extra power and fuel economy.

Because propane is near the top of the hydro-carbon tree, its boiling point is low, and its static flame speed is slow. This means that for best get-up-and-go power and economy, you need plenty of low-down ignition advance, however, you do not get any internal cooling with LPG, and hence you need to limit the top-end advance. Like un-leaded petrol, there is no lead in LPG, so hardened valve seats or inserts are required.

Editors note: GoSeeAustralia thanks the RVMAA for this feature.

The information and opinions expressed in it are not necessarily those of GoSeeAustralia.

Editor's Note also see: