Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Autogas shopping experience:

1. Compare - without doubt the biggest advantage that the Autogas offers shoppers today is the ability to compare thousands of Autogas at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.

2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about

3. Testimonials - don't know anybody that has bought a Autogas? Wrong! If the Autogas is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.

4. Questions - Got a question about Autogas then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....

5. Reputation - Never heard of the company selling Autogas? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Autogas and build up a picture of their reputation for sales, returns, customer service, delivery etc.

6. Returns - still worried that even after all of the above your Autogas wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.

7. Feedback - happy with your Autogas then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.

8. Security - check for the yellow padlock on the Autogas site before you buy, and the s after http:/ /i.e. https:// = a secure site

9. Contact - got a question about Autogas, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.

10. Payment - ready to pay for your Autogas, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.

Autogas is the common name for liquified petroleum gas when it is used as a fuel in internal combustion engines in vehicles. The same equipment is also used for similar engines in stationary engine such as generators.

Autogas is widely used as a "green" fuel as it decreases Automobile emissions control (less 20% CO2) . It has an octane rating (MON/RON) that is between 90 and 110 and an energy content (higher heating value—HHV) that is between 25.5 megajoules per litre (for pure propane) and 28.7 megajoules per litre (for pure butane.)

In countries where gasoline is called petrol rather than gasoline, it is common for autogas to be simply referred to as gas. This can be confusing for people from countries where petrol is called gasoline, as they often use the abbreviation gas to refer to petrol. In the United States, autogas is more commonly known under the name of its primary constituent, propane.

Vehicle manufacturers Toyota Motor Corporation made a number of LPG engines in their 1970s Toyota M engine, Toyota R engine, and Toyota Y engine engine families.

Currently, a number of automobile manufacturers—Citroën, Fiat, Ford Motor Company, Hyundai Motor Company, General Motors (including Daewoo, Holden, Opel/Vauxhall Motors, Saab automobile), Peugeot, Renault, Toyota and Volvo Cars—have Original equipment manufacturer bi-fuel (dual fuel) models that will run equally well on both LPG and gasoline. See list of LPG cars.

Vialli have OEM LPG powered scooters and LPG powered mopeds that run equally well on LPG. Ford Australia have offered an LPG-only variant of their Falcon model since 2000.

Countries Autogas enjoys great popularity in Turkey, Australia, The Netherlands, Italy, Serbia, Poland, Hong Kong and Korea. It is also available at larger petrol stations in England in the larger urban areas. The former Soviet republic of Armenia may, however, be the world leader in autogas use. The Armenian transport ministry estimates as much as 20 to 30% of vehicles use autogas compared with traditional gasoline, once again due to the fact that it offers a very cheap alternative to both diesel and petrol, being less than half the price of petrol and some 40% cheaper than diesel. The recent rises in oil-derived fuels has sharply raised the difference.

Europe The European standard is EN 589

Australia LPG is popular in Australia, in part due to it being less than half the price of petrol in urban areas. The four major local manufacturers (Ford Motor Company, Holden, Mitsubishi Motors and Toyota Motor Corporation) offer it in some models of their locally made large cars. All factory autogas vehicles are dual fuel vehicles, with the exception of the E-Gas Ford Falcon (Australia) model, which runs on autogas only.

Autogas is especially popular with taxis, except in remote areas where transportation costs make autogas prices uncompetitive.

Whilst LPG is currently excise-free, an excise on LPG starting at 2.5 cents per litre in 2011 will be placed, which will increase incrementally to 12.5 cents per litre (as opposed to the 38 cpl excise on petrol) by 2015. This will be offset somewhat by a AU$2000 subsidy that was implemented in 2006 for private motorists to convert their cars to LPG. The subsidy does not presently apply to business vehicles or vehicles with a Gross Vehicle Mass of over 3500 kilograms but lobbyists are trying to get that changed. On top of the subsidy to be provided by the Australian federal government, the Western Australian government will also provide motorists with a AU$1000 subsidy under the long-running LPG subsidy scheme.

System types The different autogas systems generally use the same type of filler, tanks, lines and fittings but use different components in the engine bay. Some injection systems use special tanks with circulation pumps and return lines similar to petrol fuel injection systems.

There are three basic types of autogas system. The oldest of these is the conventional converter-and-mixer system, which has existed since the 1940s and is still widely used today. The other two types are known as injection systems, but there are significant differences between the two.

A converter-mixer system uses a converter to change liquid fuel from the tank into vapour, then feeds that vapour to the mixer where it is mixed with the intake air.

Vapour phase injection systems use a converter in much the same way as with a mixer, but have a series of electrical shutoff solenoids and nozzles (collectively referred to as injectors) that are controlled by a computer. The computer works in much the same way as a petrol fuel injection computer. This allows much more accurate metering of fuel to the engine than is possible with mixers, improving economy and/or power while reducing emissions.

Liquid phase injection systems do not use a converter, but instead deliver the liquid fuel into a fuel rail in much the same manner as a petrol injection system. These systems are still very much in their infancy. Because the fuel vapourises in the intake, the air around it is cooled significantly. This increases the density of the intake air and can potentially lead to substantial increases in engine power output, to the extent that such systems are usually de-tuned to avoid damaging other parts of the engine. Liquid phase injection has the potential to achieve much better economy and power plus lower emission levels than are possible using mixers or vapour phase injectors.

System components Filler The fuel is transferred into a vehicle tank as liquid by connecting the Gas pump at the filling station to the filler fitting on the vehicle.

The type of filler used varies from country to country and in some cases different types are used within the same country .

The three types are:

Adaptors that allow a vehicle fitted with a particular system to refuel at a station equipped with another system are available.

The fill valve contains a check valve so that the liquid in the line between the filler and the tank(s) does not escape when the bowser nozzle is disconnected.

In installations where more than one tank is fitted, T-fittings may be used to connect the tanks to one filler so that the tanks are filled simultaneously. In some applications, more than one filler may be fitted, such as on opposite sides of the vehicle. These may be connected to separate tanks, or may be connected to the same tanks using T-fittings in the same manner as for connecting multiple tanks to one filler.

Hoses, pipes and fittings The hose between the filler and tank(s) is called the fill hose or fill line. The hose or pipe between the tank(s) and the converter is called the service line. These both carry liquid under pressure.

The flexible hose between the converter and mixer is called the vapour hose or vapour line. This line carries vapour at low pressure and has a much larger diameter to suit.

Where the tank valves are located inside an enclosed space such as the boot of a sedan, a plastic containment hose is used to provide a gas-tight seal between the gas components and the inside of the vehicle.

Liquid hoses for LPG are specifically designed and rated for the pressures that exist in LPG systems, and are made from materials designed to be compatible with the fuel. Some hoses are made with Crimp (joining) fittings, while others are made using re-usable fittings that are pressed or screwed onto the end of the hose.

Rigid sections of liquid line are usually made using copper tubing, although in some applications, steel pipes are used instead. The ends of the pipes are always double-flared and fitted with flare nuts to secure them to the fittings.

Liquid line fittings are mostly made from brass. The fittings typically adapt from a thread in a component, such as a British standard pipe thread or National pipe thread threaded hole on a tank, to an SAE flare fitting to suit the ends of pipes or hoses.

Tank See also: Gas cylinder Vehicles are often fitted with only one tank, but multiple tanks are used in a some applications.

The tanks have fittings for filling, liquid outlet, emergency relief of excess pressure, fuel level gauge and sometimes a vapour outlet. These may be separate valves mounted into a series of 3 to 5 holes in a plate welded into the tank shell, or may be assembled onto a multi-valve unit which is bolted into one large hole on a boss welded into the tank shell.Modern fill valves are usually fitted with an automatic fill limiter (AFL) to prevent overfilling. The AFL has a float arm which restricts the flow significantly but does not shut it off entirely. This is intended to cause the pressure in the line to rise enough to tell the bowser to stop pumping but not cause dangerously high pressures. Before AFLs were introduced, it was common for the filler (with integral check valve) to be screwed directly into the tank, as the operator had to open an ullage valve at the tank while filling, allowing vapour out of the top of the tank and stopping filling when liquid started coming out of the ullage valve to indicate that the tank was full. Modern tanks are not fitted with ullage valves.

The liquid outlet is usually used to supply fuel to the engine, and is usually referred to as the service valve. Modern service valves incorporate an electric shutoff solenoid. In applications using very small engines such as small generators, vapour may be withdrawn from the top of the tank instead of liquid from the bottom of the tank.

The emergency pressure relief valve in the tank is called a hydrostatic pressure relief valve. It is designed to open if the pressure in the tank is dangerously high, thus releasing some vapour to the atmosphere to reduce the pressure in the tank. The release of a small quantity of vapour reduces the pressure in the tank, which causes some of the liquid in the tank to vapourise to re-establish equilibrium between liquid and vapour. The latent heat of vapourisation causes the tank to cool, which reduces pressure even further.

The gauge sender is usually a magnetically coupled arrangement, with a float arm inside the tank rotating a magnet, which rotates an external gauge. The external gauge is usually readable directly, and most also incorporate an electronic sender to operate a fuel gauge on the dashboard.

Valves There are a number of types of valve used in autogas systems. The most common ones are shutoff or filterlock valves, which are used to stop flow in the service line. These may be operated by vacuum or electricity. On dual-fuel systems with a petrol carburettor, a similar shutoff valve is usually fitted in the petrol line between the pump and carburettor.

Check valves are fitted in the filler and on the fill input to the fuel tank to prevent fuel flowing back the wrong way.

Service valves are fitted to the outlet from the tank to the service line. These have a tap to turn the fuel on and off. The tap is usually only closed when the tank is being worked on. In some countries, an electrical shutoff valve is built into the service valve.

Where multiple tanks are fitted, a combination of check valves and a hydrostatic relief valve are usually installed to prevent fuel from flowing from one tank to another. In Australia, there is a common assembly designed for this purpose. It is a combined twin check valve and hydrostatic relief valve assembly built in the form of a T-fitting, such that the lines from the tanks come into the sides of the valve and the outlet to the converter comes out the end. Because there is only one common brand of these valves, they are known colloquially as a Sherwood valve.

Converter The converter (also known as vaporiser) is a device designed to change the fuel from a pressurised liquid to a vapour at around atmospheric pressure for delivery to the mixer or vapour phase injectors. Because of the refrigerant characteristic of the fuel, heat must be put into the fuel by the converter. This is usually achieved by having engine coolant circulated through a heat exchanger that transfers heat from that coolant to the LPG.

There are two distinctly different basic types of converter for use with mixer type systems. The European style of converter is a more complex device that incorporates an idle circuit and is designed to be used with a simple fixed venturi mixer. The American style of converter is a simpler design which is intended to be used with a variable venturi mixer that incorporates an idle circuit.

Engines with a low power output such as; scooters, quad bikes and generators can use a simpler type of converter (also known as governor or regulator). These converters are fed with fuel in vapour form.Evaporation takes place in the tank where refrigeration occurs as the liquid fuel boils. The tanks large surface area exposed to the ambient air temperature combined with the low power output (fuel requirement) of the engine make this type of system viable. The refrigeration of the fuel tank is proportional to fuel demand hence this setup is only used on smaller engines.This type of converter can either fed with vapour at tank pressure (called a 2 stage regulator) or be fed via a tank mounted regulator at a fixed reduced pressure (called a single stage regulator).



Mixer The mixer is the device that mixes the fuel into the air flowing to the engine. The mixer incorporates a venturi pump designed to draw the fuel into the airflow due to the movement of the air.

Mixer type systems have existed since the 1940s and some designs have changed little over that time. Mixers are now being increasingly superseded by injectors.

Vapour phase injectors Most vapour phase injection systems mount the solenoids in a manifold block or injector rail, then run hoses to the nozzles, which are screwed into holes drilled and tapped into the runners of the intake manifold. There is usually one nozzle for each cylinder. Some vapour injection systems resemble petrol injection, having separate injectors that fit into the manifold or head in the same manner as petrol injectors, and are fed fuel through a fuel rail.

Liquid phase injectors Liquid phase injectors are mounted onto the engine in a manner similar to petrol injectors, being mounted directly at the inlet manifold and fed liquid fuel from a fuel rail.

Electrical and electronic controls The are four distinct electrical systems that may be used in autogas systems - fuel gauge sender, fuel shutoff, Control theory feedback mixture control and injection control.

In some installations, the fuel gauge sender fitted to the autogas tank is matched to the original fuel gauge in the vehicle. In others, an additional gauge is added to display the level of fuel in the autogas tank separately from the existing petrol gauge.

In most modern installations, an electronic device called a tachometric relay or safety switch is used to operate electrical shutoff solenoids. These work by sensing that the engine is running by detecting ignition pulses. Some systems use an engine oil pressure sensor instead. In all installations, there is a filterlock (consisting of a filter assembly and a vacuum or electric solenoid operated shutoff valve) located at the input to the converter. In European converters, there is also a solenoid in the converter to shut off the idle circuit. These valves are usually both connected to the output of the tachometric relay or oil pressure switch. Where solenoids are fitted to the outputs of fuel tanks, these are also connected to the output of the tachometric relay or oil pressure switch. In installations with multiple tanks, a switch or changeover relay may be fitted to allow the driver to select which tank to use fuel from. On dual-fuel systems, the switch used to change between fuels is used to turn off the tachometric relay.

Closed loop feedback systems use an electronic controller that operates in much the same way as in a petrol fuel injection systems, using an oxygen sensor to effectively measure the air/fuel mixture by measuring the oxygen content of the exhaust and control valve on the converter or in the vapour line to adjust the mixture. Mixer type systems that do not have a closed loop feedback fitted are sometimes referred to as open loop systems.

Injection systems use a computerised control system which is very similar to that used in petrol injection systems. In virtually all systems, the injection control system integrates the tachometric relay and closed loop feedback functions.

Converter-and-mixer system operation The designs of converters and mixers are matched to each other by matching sizes and shapes of components within the two.

In European style systems, the size and shape of the venturi is designed to match the converter. In American style systems, the air valve and metering pins in the mixer are sized to match the diaphragm sizes and spring stiffnesses in the converter. In both cases, the components are matched by the manufacturers and only basic adjustments are needed during installation and tuning.

An autogas carburettor simply consists of a throttlebody and a mixer, sometimes fitted together using an adapter.

Cold start enrichment is achieved by the fact that the engine coolant is cold when the engine is cold. This causes denser vapour to be delivered to the mixer. As the engine warms up, the coolant temperature rises until the engine is at operating temperature and the mixture has leaned off to the normal running mixture. Depending on the system, the throttle may need to be held open further when the engine is cold in the same manner as with a petrol carburetor. On others, the normal mixture is intended to be somewhat lean and no cold-start throttle increase is needed. Because of the way enrichment is achieved, no additional choke butterfly is required for cold starting with LPG.

The temperature of the engine is critical to the tuning of an autogas system. The engine thermostat effectively controls the temperature of the converter, thus directly affecting the mixture. A faulty thermostat, or a thermostat of the wrong temperature range for the design of the system may not operate correctly.

The power output capacity of a system is limited by the ability of the converter to deliver a stable flow of vapour. A coolant temperature lower than intended will reduce the maximum power output possible, as will an air bubble trapped in the cooling circuit or complete loss of coolant. All converters have a limit, beyond which mixtures become unstable. Unstable mixtures typically contain tiny droplets of liquid fuel that were not heated enough in the converter and will vapourise in the mixer or intake to form an excessively rich mixture. When this occurs, the mixture will become so rich that the engine will flood and stall. Because the outside of the converter will be at or below zero degrees Celsius when this happens, water vapour from the air will freeze onto the outside of the converter, forming an icy white layer. Some converters are very suceptible to cracking when this happens.

Performance The Yellow-Checker-Star taxi fleet of Las Vegas, NV is a well known propane user. These taxis are mostly production gasoline Crown Victoria conversions. When the larger propane fuel tank replaces the smaller gasoline tank, about 1/8 of the trunk space is lost. Maximum distance varies between 250 to 320 miles on one full tank. Fuel capacity varies a great deal with ambient temperature. On the coldest desert winter nights taxis might travel up to 400 miles or more. But on the hottest summer days taxis might achieve only 180 miles. When it is very hot, refuelling requires extra time. This can cause long lines to form at refuelling stations, particularly during shift changes.

It's a common rule of thumb in Australia that a dual fuel car will use about 20-30% more fuel than an equivalent petrol car, and has slightly less power. Modern injection systems are making the gap smaller, however, as do dedicated LPG systems, since they do not have to be able to run both LPG and petrol. In some cases, LPG engines can actually have more power and torque and similar economy when compared with an equivalent petrol engine.

LPG injection for diesel vehicles The performance, economy and emission profile of diesel engines can be improved by injecting a small quantity of LPG into the inlet manifold. It is claimed that the LPG increases the burning efficiency of the diesel fuel from typically 75-85%, to 95-98%.

The systems typically operate by metering a small quantity of LPG, at a pressure slightly above atmospheric, into the intake manifold, where it enters the combustion chamber and is ignited with the diesel. LPG flow is regulated to ensure smooth operation, and will typically only deliver LPG under power.

Some companies claim a 10% to 20% increase in power and torque , and a reduction in overall fuel costs. Any actual savings are dependent on the relative cost of diesel versus LPG. In Australia, where diesel costs substantially more than LPG, savings of 10 to 20% are claimed.

See also

External links and references

Autogas is the common name for liquified petroleum gas when it is used as a fuel in internal combustion engines in vehicles. The same equipment is also used for similar engines in stationary engine such as generators.

Autogas is widely used as a "green" fuel as it decreases Automobile emissions control (less 20% CO2) . It has an octane rating (MON/RON) that is between 90 and 110 and an energy content (higher heating value—HHV) that is between 25.5 megajoules per litre (for pure propane) and 28.7 megajoules per litre (for pure butane.)

In countries where gasoline is called petrol rather than gasoline, it is common for autogas to be simply referred to as gas. This can be confusing for people from countries where petrol is called gasoline, as they often use the abbreviation gas to refer to petrol. In the United States, autogas is more commonly known under the name of its primary constituent, propane.

Vehicle manufacturers Toyota Motor Corporation made a number of LPG engines in their 1970s Toyota M engine, Toyota R engine, and Toyota Y engine engine families.

Currently, a number of automobile manufacturers—Citroën, Fiat, Ford Motor Company, Hyundai Motor Company, General Motors (including Daewoo, Holden, Opel/Vauxhall Motors, Saab automobile), Peugeot, Renault, Toyota and Volvo Cars—have Original equipment manufacturer bi-fuel (dual fuel) models that will run equally well on both LPG and gasoline. See list of LPG cars.

Vialli have OEM LPG powered scooters and LPG powered mopeds that run equally well on LPG. Ford Australia have offered an LPG-only variant of their Falcon model since 2000.

Countries Autogas enjoys great popularity in Turkey, Australia, The Netherlands, Italy, Serbia, Poland, Hong Kong and Korea. It is also available at larger petrol stations in England in the larger urban areas. The former Soviet republic of Armenia may, however, be the world leader in autogas use. The Armenian transport ministry estimates as much as 20 to 30% of vehicles use autogas compared with traditional gasoline, once again due to the fact that it offers a very cheap alternative to both diesel and petrol, being less than half the price of petrol and some 40% cheaper than diesel. The recent rises in oil-derived fuels has sharply raised the difference.

Europe The European standard is EN 589

Australia LPG is popular in Australia, in part due to it being less than half the price of petrol in urban areas. The four major local manufacturers (Ford Motor Company, Holden, Mitsubishi Motors and Toyota Motor Corporation) offer it in some models of their locally made large cars. All factory autogas vehicles are dual fuel vehicles, with the exception of the E-Gas Ford Falcon (Australia) model, which runs on autogas only.

Autogas is especially popular with taxis, except in remote areas where transportation costs make autogas prices uncompetitive.

Whilst LPG is currently excise-free, an excise on LPG starting at 2.5 cents per litre in 2011 will be placed, which will increase incrementally to 12.5 cents per litre (as opposed to the 38 cpl excise on petrol) by 2015. This will be offset somewhat by a AU$2000 subsidy that was implemented in 2006 for private motorists to convert their cars to LPG. The subsidy does not presently apply to business vehicles or vehicles with a Gross Vehicle Mass of over 3500 kilograms but lobbyists are trying to get that changed. On top of the subsidy to be provided by the Australian federal government, the Western Australian government will also provide motorists with a AU$1000 subsidy under the long-running LPG subsidy scheme.

System types The different autogas systems generally use the same type of filler, tanks, lines and fittings but use different components in the engine bay. Some injection systems use special tanks with circulation pumps and return lines similar to petrol fuel injection systems.

There are three basic types of autogas system. The oldest of these is the conventional converter-and-mixer system, which has existed since the 1940s and is still widely used today. The other two types are known as injection systems, but there are significant differences between the two.

A converter-mixer system uses a converter to change liquid fuel from the tank into vapour, then feeds that vapour to the mixer where it is mixed with the intake air.

Vapour phase injection systems use a converter in much the same way as with a mixer, but have a series of electrical shutoff solenoids and nozzles (collectively referred to as injectors) that are controlled by a computer. The computer works in much the same way as a petrol fuel injection computer. This allows much more accurate metering of fuel to the engine than is possible with mixers, improving economy and/or power while reducing emissions.

Liquid phase injection systems do not use a converter, but instead deliver the liquid fuel into a fuel rail in much the same manner as a petrol injection system. These systems are still very much in their infancy. Because the fuel vapourises in the intake, the air around it is cooled significantly. This increases the density of the intake air and can potentially lead to substantial increases in engine power output, to the extent that such systems are usually de-tuned to avoid damaging other parts of the engine. Liquid phase injection has the potential to achieve much better economy and power plus lower emission levels than are possible using mixers or vapour phase injectors.

System components Filler The fuel is transferred into a vehicle tank as liquid by connecting the Gas pump at the filling station to the filler fitting on the vehicle.

The type of filler used varies from country to country and in some cases different types are used within the same country .

The three types are:

Adaptors that allow a vehicle fitted with a particular system to refuel at a station equipped with another system are available.

The fill valve contains a check valve so that the liquid in the line between the filler and the tank(s) does not escape when the bowser nozzle is disconnected.

In installations where more than one tank is fitted, T-fittings may be used to connect the tanks to one filler so that the tanks are filled simultaneously. In some applications, more than one filler may be fitted, such as on opposite sides of the vehicle. These may be connected to separate tanks, or may be connected to the same tanks using T-fittings in the same manner as for connecting multiple tanks to one filler.

Hoses, pipes and fittings The hose between the filler and tank(s) is called the fill hose or fill line. The hose or pipe between the tank(s) and the converter is called the service line. These both carry liquid under pressure.

The flexible hose between the converter and mixer is called the vapour hose or vapour line. This line carries vapour at low pressure and has a much larger diameter to suit.

Where the tank valves are located inside an enclosed space such as the boot of a sedan, a plastic containment hose is used to provide a gas-tight seal between the gas components and the inside of the vehicle.

Liquid hoses for LPG are specifically designed and rated for the pressures that exist in LPG systems, and are made from materials designed to be compatible with the fuel. Some hoses are made with Crimp (joining) fittings, while others are made using re-usable fittings that are pressed or screwed onto the end of the hose.

Rigid sections of liquid line are usually made using copper tubing, although in some applications, steel pipes are used instead. The ends of the pipes are always double-flared and fitted with flare nuts to secure them to the fittings.

Liquid line fittings are mostly made from brass. The fittings typically adapt from a thread in a component, such as a British standard pipe thread or National pipe thread threaded hole on a tank, to an SAE flare fitting to suit the ends of pipes or hoses.

Tank See also: Gas cylinder Vehicles are often fitted with only one tank, but multiple tanks are used in a some applications.

The tanks have fittings for filling, liquid outlet, emergency relief of excess pressure, fuel level gauge and sometimes a vapour outlet. These may be separate valves mounted into a series of 3 to 5 holes in a plate welded into the tank shell, or may be assembled onto a multi-valve unit which is bolted into one large hole on a boss welded into the tank shell.Modern fill valves are usually fitted with an automatic fill limiter (AFL) to prevent overfilling. The AFL has a float arm which restricts the flow significantly but does not shut it off entirely. This is intended to cause the pressure in the line to rise enough to tell the bowser to stop pumping but not cause dangerously high pressures. Before AFLs were introduced, it was common for the filler (with integral check valve) to be screwed directly into the tank, as the operator had to open an ullage valve at the tank while filling, allowing vapour out of the top of the tank and stopping filling when liquid started coming out of the ullage valve to indicate that the tank was full. Modern tanks are not fitted with ullage valves.

The liquid outlet is usually used to supply fuel to the engine, and is usually referred to as the service valve. Modern service valves incorporate an electric shutoff solenoid. In applications using very small engines such as small generators, vapour may be withdrawn from the top of the tank instead of liquid from the bottom of the tank.

The emergency pressure relief valve in the tank is called a hydrostatic pressure relief valve. It is designed to open if the pressure in the tank is dangerously high, thus releasing some vapour to the atmosphere to reduce the pressure in the tank. The release of a small quantity of vapour reduces the pressure in the tank, which causes some of the liquid in the tank to vapourise to re-establish equilibrium between liquid and vapour. The latent heat of vapourisation causes the tank to cool, which reduces pressure even further.

The gauge sender is usually a magnetically coupled arrangement, with a float arm inside the tank rotating a magnet, which rotates an external gauge. The external gauge is usually readable directly, and most also incorporate an electronic sender to operate a fuel gauge on the dashboard.

Valves There are a number of types of valve used in autogas systems. The most common ones are shutoff or filterlock valves, which are used to stop flow in the service line. These may be operated by vacuum or electricity. On dual-fuel systems with a petrol carburettor, a similar shutoff valve is usually fitted in the petrol line between the pump and carburettor.

Check valves are fitted in the filler and on the fill input to the fuel tank to prevent fuel flowing back the wrong way.

Service valves are fitted to the outlet from the tank to the service line. These have a tap to turn the fuel on and off. The tap is usually only closed when the tank is being worked on. In some countries, an electrical shutoff valve is built into the service valve.

Where multiple tanks are fitted, a combination of check valves and a hydrostatic relief valve are usually installed to prevent fuel from flowing from one tank to another. In Australia, there is a common assembly designed for this purpose. It is a combined twin check valve and hydrostatic relief valve assembly built in the form of a T-fitting, such that the lines from the tanks come into the sides of the valve and the outlet to the converter comes out the end. Because there is only one common brand of these valves, they are known colloquially as a Sherwood valve.

Converter The converter (also known as vaporiser) is a device designed to change the fuel from a pressurised liquid to a vapour at around atmospheric pressure for delivery to the mixer or vapour phase injectors. Because of the refrigerant characteristic of the fuel, heat must be put into the fuel by the converter. This is usually achieved by having engine coolant circulated through a heat exchanger that transfers heat from that coolant to the LPG.

There are two distinctly different basic types of converter for use with mixer type systems. The European style of converter is a more complex device that incorporates an idle circuit and is designed to be used with a simple fixed venturi mixer. The American style of converter is a simpler design which is intended to be used with a variable venturi mixer that incorporates an idle circuit.

Engines with a low power output such as; scooters, quad bikes and generators can use a simpler type of converter (also known as governor or regulator). These converters are fed with fuel in vapour form.Evaporation takes place in the tank where refrigeration occurs as the liquid fuel boils. The tanks large surface area exposed to the ambient air temperature combined with the low power output (fuel requirement) of the engine make this type of system viable. The refrigeration of the fuel tank is proportional to fuel demand hence this setup is only used on smaller engines.This type of converter can either fed with vapour at tank pressure (called a 2 stage regulator) or be fed via a tank mounted regulator at a fixed reduced pressure (called a single stage regulator).



Mixer The mixer is the device that mixes the fuel into the air flowing to the engine. The mixer incorporates a venturi pump designed to draw the fuel into the airflow due to the movement of the air.

Mixer type systems have existed since the 1940s and some designs have changed little over that time. Mixers are now being increasingly superseded by injectors.

Vapour phase injectors Most vapour phase injection systems mount the solenoids in a manifold block or injector rail, then run hoses to the nozzles, which are screwed into holes drilled and tapped into the runners of the intake manifold. There is usually one nozzle for each cylinder. Some vapour injection systems resemble petrol injection, having separate injectors that fit into the manifold or head in the same manner as petrol injectors, and are fed fuel through a fuel rail.

Liquid phase injectors Liquid phase injectors are mounted onto the engine in a manner similar to petrol injectors, being mounted directly at the inlet manifold and fed liquid fuel from a fuel rail.

Electrical and electronic controls The are four distinct electrical systems that may be used in autogas systems - fuel gauge sender, fuel shutoff, Control theory feedback mixture control and injection control.

In some installations, the fuel gauge sender fitted to the autogas tank is matched to the original fuel gauge in the vehicle. In others, an additional gauge is added to display the level of fuel in the autogas tank separately from the existing petrol gauge.

In most modern installations, an electronic device called a tachometric relay or safety switch is used to operate electrical shutoff solenoids. These work by sensing that the engine is running by detecting ignition pulses. Some systems use an engine oil pressure sensor instead. In all installations, there is a filterlock (consisting of a filter assembly and a vacuum or electric solenoid operated shutoff valve) located at the input to the converter. In European converters, there is also a solenoid in the converter to shut off the idle circuit. These valves are usually both connected to the output of the tachometric relay or oil pressure switch. Where solenoids are fitted to the outputs of fuel tanks, these are also connected to the output of the tachometric relay or oil pressure switch. In installations with multiple tanks, a switch or changeover relay may be fitted to allow the driver to select which tank to use fuel from. On dual-fuel systems, the switch used to change between fuels is used to turn off the tachometric relay.

Closed loop feedback systems use an electronic controller that operates in much the same way as in a petrol fuel injection systems, using an oxygen sensor to effectively measure the air/fuel mixture by measuring the oxygen content of the exhaust and control valve on the converter or in the vapour line to adjust the mixture. Mixer type systems that do not have a closed loop feedback fitted are sometimes referred to as open loop systems.

Injection systems use a computerised control system which is very similar to that used in petrol injection systems. In virtually all systems, the injection control system integrates the tachometric relay and closed loop feedback functions.

Converter-and-mixer system operation The designs of converters and mixers are matched to each other by matching sizes and shapes of components within the two.

In European style systems, the size and shape of the venturi is designed to match the converter. In American style systems, the air valve and metering pins in the mixer are sized to match the diaphragm sizes and spring stiffnesses in the converter. In both cases, the components are matched by the manufacturers and only basic adjustments are needed during installation and tuning.

An autogas carburettor simply consists of a throttlebody and a mixer, sometimes fitted together using an adapter.

Cold start enrichment is achieved by the fact that the engine coolant is cold when the engine is cold. This causes denser vapour to be delivered to the mixer. As the engine warms up, the coolant temperature rises until the engine is at operating temperature and the mixture has leaned off to the normal running mixture. Depending on the system, the throttle may need to be held open further when the engine is cold in the same manner as with a petrol carburetor. On others, the normal mixture is intended to be somewhat lean and no cold-start throttle increase is needed. Because of the way enrichment is achieved, no additional choke butterfly is required for cold starting with LPG.

The temperature of the engine is critical to the tuning of an autogas system. The engine thermostat effectively controls the temperature of the converter, thus directly affecting the mixture. A faulty thermostat, or a thermostat of the wrong temperature range for the design of the system may not operate correctly.

The power output capacity of a system is limited by the ability of the converter to deliver a stable flow of vapour. A coolant temperature lower than intended will reduce the maximum power output possible, as will an air bubble trapped in the cooling circuit or complete loss of coolant. All converters have a limit, beyond which mixtures become unstable. Unstable mixtures typically contain tiny droplets of liquid fuel that were not heated enough in the converter and will vapourise in the mixer or intake to form an excessively rich mixture. When this occurs, the mixture will become so rich that the engine will flood and stall. Because the outside of the converter will be at or below zero degrees Celsius when this happens, water vapour from the air will freeze onto the outside of the converter, forming an icy white layer. Some converters are very suceptible to cracking when this happens.

Performance The Yellow-Checker-Star taxi fleet of Las Vegas, NV is a well known propane user. These taxis are mostly production gasoline Crown Victoria conversions. When the larger propane fuel tank replaces the smaller gasoline tank, about 1/8 of the trunk space is lost. Maximum distance varies between 250 to 320 miles on one full tank. Fuel capacity varies a great deal with ambient temperature. On the coldest desert winter nights taxis might travel up to 400 miles or more. But on the hottest summer days taxis might achieve only 180 miles. When it is very hot, refuelling requires extra time. This can cause long lines to form at refuelling stations, particularly during shift changes.

It's a common rule of thumb in Australia that a dual fuel car will use about 20-30% more fuel than an equivalent petrol car, and has slightly less power. Modern injection systems are making the gap smaller, however, as do dedicated LPG systems, since they do not have to be able to run both LPG and petrol. In some cases, LPG engines can actually have more power and torque and similar economy when compared with an equivalent petrol engine.

LPG injection for diesel vehicles The performance, economy and emission profile of diesel engines can be improved by injecting a small quantity of LPG into the inlet manifold. It is claimed that the LPG increases the burning efficiency of the diesel fuel from typically 75-85%, to 95-98%.

The systems typically operate by metering a small quantity of LPG, at a pressure slightly above atmospheric, into the intake manifold, where it enters the combustion chamber and is ignited with the diesel. LPG flow is regulated to ensure smooth operation, and will typically only deliver LPG under power.

Some companies claim a 10% to 20% increase in power and torque , and a reduction in overall fuel costs. Any actual savings are dependent on the relative cost of diesel versus LPG. In Australia, where diesel costs substantially more than LPG, savings of 10 to 20% are claimed.

See also

External links and references



LPG from Autogas Ltd
Provides information on environmental and monetary savings, LPG conversions and retailing autogas.

LPG Vehicles
LPG can save up to 50% on your fuel bills - Calor Autogas is the brand of automotive liquefied petroleum gas (LPG) marketed by calor to the UK automotive industry.

Autogas 2000 Ltd
Alternative fuel conversion specialists and autogas refueling stations in the UK ... Welcome to the Autogas 2000 Ltd web site   Autogas 2000 Ltd is a family owned company ...

Shell Gas (LPG) UK - LPG, today’s fuel for tomorrow's environment
Supplying liquid petroleum gas to domestic and industrial customers in UK.

National Autogas | For all your Autogas / Liquefied Petroleum Gas (LPG ...
National Autogas, taking care of all your Autogas / Liquefied Petroleum Gas (LPG) Conversion needs for Installers and Consumers ...

Autogas Gas Conversions.....Autogas 2000 Ltd
UK2NET UK2.NET UK'S FREE DOMAIN NAMES ... Welcome to the Autogas 2000 Ltd web site   Autogas 2000 Ltd is a family owned company, specialising for nearly 30 years in the ...

Autogas Worldwide - LPG Vehicle Conversions throughout the UK
LPG (Autogas) Training and Conversions available nationwide by agw-romano approved centres ... for information about the history and development of LPG systems for vehicles.

We specialise in the conversion of vehicles to use LPG (Autogas ...
Specialises in LPG vehicle conversions for all vehicles.

FES Autogas - LPG- Conversions
Where The Gas Is Always Greener ! © 2008. Ever wanted to be able to run your car and still have money left in your pocket?

PREMIER AUTOGAS
Premier Autogas, Premier LPG, Autogas, LPG, Forecourt, Fleet, Forklift Truck, FLT ... PREMIER LPG is the leading independent supplier of Liquefied Petroleum ...

 

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