Technology of autogas vehicles

vehicles running on autogas are usually started on petrol and then, depending on the system installed, switched manually by the driver (switch in the cockpit) or automatically to autogas operation (or switched back to petrol when the gas tank is empty).

This avoids possible warm up problems. Automatic changeover is preferable to manual changeover, as this avoids engine damage and icing up of the gas system. The systems installed by specialized workshops switch over automatically and ensure practically smooth switching between fuels even while driving.

Autogas tank gauge and switch panel in the ashtray of a BMW 3 series (click to enlarge).

1. The different types of autogas systems

A basic distinction is made between venturi systems, sequential systems and systems with liquid injection (sog. Lpdi or DI systems) are distinguished. All three types of systems are described here. From a technical point of view, certain types of systems are preferable, depending on the vehicle and its performance. This is where the experience of the respective conversion store is particularly important with regard to the conversion capability of individual vehicles and models, as no recommendations are made here by the car manufacturers themselves. As with everything in life, quality also has its price here. Therefore, when converting to autogas, you should also consider the mileage of the vehicle in question.

Evaporator plants (venturi and sequential plants) have in common that the liquid autogas under pressure in the tank (see autogas fuel / LPG) is fed to the engine in gaseous form through an evaporator and pressure regulator. Since autogas (LPG) cools down a lot during evaporation, the evaporator is heated with cooling water. this is also the reason why modern autogas systems are only available from approx. 30° celsius cooling water temperature switch to autogas. This effectively prevents the gas system from icing up at low outside temperatures. Since 2010, special systems for engines with gasoline direct injection (FSI, TSI, etc.) are also available.) offered. A distinction is made here between autogas systems with gasoline admixture (z. B. Prins VSI-DI system) or liquid injection systems (z.B. Vialle lpdi).

Autogas components in the vehicle (click on the image to enlarge).

Venturi technology

venturi technology is the oldest and most cost-effective system technology. In venturi systems, a vacuum-controlled metering valve is mounted in the intake manifold, which meters autogas in a vacuum-controlled manner. Due to the narrowing of the intake cross-section, a slight loss of power and increased fuel consumption can be expected as a result of the system. In addition, this type of system can lead to back combustion in the intake tract. This phenomenon, known as backfire, can occur if the ignition system fails to ignite the autogas that is constantly present in the intake tract with this technology. In common venturin systems, however, damage caused by backfire is prevented by installed pressure relief valves in the intake manifolds and/or in the air filter boxes, which allow the pressure generated in the event of an explosion to escape safely. The venturi technology is suitable up to emissions standard euro 2 (or. Partly also D3) suitable without loss of a tax class.

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Sequential autogas systems

  • Partially sequential autogas systems

Partial sequence systems use a more precise electronically controlled metering valve. This system feeds the autogas into the intake manifolds of the cylinders by means of a star-shaped gas distributor. There is no cross-section narrowing in the intake tract and thus no loss of power; the backfire is eliminated. Partially sequential systems often have a programmable map sensor for autogas operation, which is why this system technology is particularly suitable for older cars and passenger cars up to the euro 3 emissions standard.

Fully sequential autogas systems can be considered as state of the art vaporizer systems. This type of system has its own metering valve per cylinder. An autonomous map computer is completely unnecessary. Instead, the injection map stored in the on-board computer converts gasoline to equivalent autogas quantities. LPG conversion and programming are easier to carry out than with other vaporizer systems. However, the prerequisite is sequential or group sequential gasoline injection of the motor vehicle to be converted. Many vehicles registered since mid-1995 already feature this technology, which is due to the introduction of the euro 3 and euro 4 emission standards, which made gasoline injection mandatory. Your autogas retrofitter will tell you whether your vehicle belongs to this category.
By using a fully sequential system, the euro 4 emission standard can usually be achieved without any problems. in any case, after an autogas conversion to a fully sequential system, an emission confirmation for the currently valid emission standard is required, otherwise an acceptance (TuV) in germany is not to be obtained.

2. LPG systems for direct injection gasoline engines (FSI, TSI, sci etc).)

An increasing number of modern vehicles are now equipped with a gasoline direct injection engine. This technology is designed to save fuel and make the engines even more powerful. However, problems can arise when using conventional fully sequential autogas systems in engines with direct injection in gas operation. With the exception of a few converters, until recently hardly anyone dared to use direct injection engines such as z. B. FSI or TSI engine conversion. However, against the backdrop of an ever-growing market for gasoline direct injection vehicles, there are now new, reliable systems that make the conversion of gasoline direct injection engines possible in the first place. You should make sure that the systems listed below have been approved by the gas system manufacturer for your vehicle and model (!) are already approved. The ever-growing list of vehicles with FSI and TSI engines that can be converted, z. B. On the prins VSI-DI system, you can find here.

Systems available on the market for vehicles with direct injection such as z. B. The lpdi systems from vialle or the VSI-DI systems from the Dutch system manufacturer prins are specially designed for engines with modern gasoline injection (FSI, TSI etc). Engine-specific systems are available depending on the engine and direct injection technology of the vehicle manufacturer. This is to ensure optimum compatibility for as many vehicle models as possible. As a result, autogas systems for vehicles with direct injection are relatively expensive compared to vaporization systems, as the systems are usually tailored to a specific manufacturer or model. Optimized for this. As a result, manufacturers can only produce small numbers of units and are currently concentrating primarily on mass manufacturers such as VW and its group brands audi and skoda. Corresponding systems are not yet available for all models and model years.

Currently, both the Dutch manufacturer vialle as well as by the likewise dutch gas system specialist prins proven gas systems for direct injection engines available:

Prins VSI-DI
since the end of 2009, the dutch manufacturer prins retrofit solutions for certain vehicles with direct injection. In contrast to the fully sequential VSI system, the new VSI DI system is not a universal system, but rather a dedicated system, which means that the system is tailored from the programming of the software to each vehicle model individually. For this reason, the manufacturer can only produce smaller quantities of the VSI-DI system than its universal fully sequential VSI system and is currently concentrating primarily on mass manufacturers such as VW and its group brands VW, audi, skoda and seat. Recently, a system for the opel zafira-B is also available. The constantly growing list of vehicles with direct injection for which the VSI-DI system has been approved by the manufacturer prins can be found here.
The specification of the VSI DI system is also reflected in the higher price compared to others normal fully sequential systems again. From a technical point of view, the Prins VSI DI system is based on the fully sequential VSI system. The VSI-DI system contains the same components as the VSI. however, both systems differ in their injection module. In contrast to liquid injection in the lpdi system of the co-injector vialle (see below), in the prins VSI-DI, the autogas (LPG) is converted to a gaseous aggregate state via the vaporizer and blown into the intake tract via the injectors, as in the fully sequential systems. An important technical difference between the two systems is that in the VSI-DI, additional gasoline is injected during gas operation (ca. 5 to 10 % depending on temperature). This major functional difference from the normal fully sequential systems is explained by the location of the gasoline injectors in direct injection engines. In FSI engines, for example, the gasoline injectors are located in the cylinder head, where the temperature is very high. The additionally injected gasoline has the function of cooling the gasoline injectors, because otherwise they would burn in gas mode. A positive side effect of the additional gasoline supply is the continuous lubrication of the valves and valve seats. This eliminates the need to fill tanks with additional additives (e.g., fuel additives).B. Flashlube) to be installed. On the other hand, these systems pay for themselves for direct injection engines (FSI, TSI, etc.)..) a little slower due to the addition of gasoline.

Advantages at a glance:

  • Conversion of many models of the VW group as well as the opel zafira-B possible
  • Suitable for direct injection engines up to euro 5
  • Dedicated system: software specially tailored to the respective vehicle model
  • Dedicated system: offered by many autogas converters

Vialle lpdi
vialle alternative fuel systems autogas systems are available in germany since 2007. vialle recently launched its latest lpdi plant for direct injection engines. the lpdi system was developed on the basis of the lpi (liquid propane injection) system from vialle. In both the lpdi system and the lpi system, the autogas (LPG) remains in a liquid state prior to combustion, unlike all vaporizer systems available on the market (venturi or fully sequential), d. H. Is not gasified before. Therefore, no intervention in the cooling circuit of the engine is necessary during the conversion. Due to the liquid injection into the suction pipes of the intake manifold, d. H. The direct injection of the autogas fuel into the cylinders, should improve the cooling of the combustion chambers, effectively protect valves and valve seats.

Other standard components remain in the vehicle that might have to be replaced in other systems. These include, for example, the high-pressure pump and the gasoline injectors.

normal autogas systems can only start operating when the engine has reached a certain temperature. With the vialle lpdi, there is no need for such a waiting period, as the system can be started directly with autogas / lpg liquid gas – if the driver so wishes, as manual switching remains possible. A gasoline-powered starting phase until the engine has reached operating temperature is superfluous with the vialle lpdi. Among other things, this is due to the system used to secure the fuel supply. A pump with a pressure of 100 bar injects the autogas liquid gas directly into the combustion chamber. This means that no changes have to be made to the electronics and the vehicle remains almost in its original condition.

Depending on the engine and direct injection technology of the vehicle manufacturer, vialle offers an engine-specific lpd system. The aim is to ensure optimum compatibility for as many vehicle models as possible. Owners of newer vehicles from the VW group and Ford can currently benefit from lpdi systems. For the first time, a specific autogas system is available for Ford engines with direct gasoline injection. Systems for various other mass producers to follow.

Vialle systems are installed in certified vialle centers like z. B. Hager autogas service converted in berlin.

Advantages at a glance:

  • Conversion of many VW Group and Ford models possible
  • suitable for direct injection engines up to euro 5
  • Automotive-specific systems
  • Dedicated system: gasoline-driven warm-up phase and permanent gasoline admixture are eliminated

Which system is better?
Opinions differ on the question of which system is better suited to vehicles with direct injection engines. Depending on the manufacturer or. If a supplier cooperates with a workshop, they will recommend an appropriate system. As different as the prins VSI-DI and the vialle lpdi may be from a technical point of view, they both inject autogas (LPG) reliably. The question "Which system is better??" will probably remain unanswered for the time being, just like the question of whether BMW or mercedes produces the better vehicles.

3. Autogas systems for diesel vehicles

Autogas systems for diesel-vehicles are currently still a long way from market maturity. Nevertheless, there are some promising approaches. The most promising concept is the 63. The new system was presented at the 62nd International Motor Show (IAA) simfuel autogas (LPG) solution from the well-known german automotive supply and system supplier huber group. The simfuel autogas system works – as the name suggests – on the principle of simultanious fueling. In this procedure at the same time autogas (LPG) and diesel fuel injected, whereby the autogas content can be up to 40 percent, depending on the time of operation. The huber group’s diesel autogas system is designed for use in SUVs / off-road vehicles and light commercial vehicles with sufficient nitrogen dioxide (NO2) and nitrogen monoxide (NO ) reduction through selective catalytic reduction (SCR). By simultaneously integrating an SCR system, the problematic nitrogen oxides can be converted into harmless nitrogen (N2) in a catalytic process by means of urea injection. If euro 6 emission values are to be achieved in this way, the final approval of the system for diesel vehicles for dual fuel use in the autogas/diesel sector in germany is still pending.

Against the background of lower diesel fuel prices, an autogas conversion of a diesel car is not economically viable at present, especially as the costs of converting a diesel vehicle on the basis of the solution described above cannot yet be quantified. the only exception is the conversion of boat engines and gensets.

LPG and diesel commercial vehicles / trucks

The development of autogas/LPG-supported systems in the commercial vehicle sector is proving very promising. In view of the increasing environmental impact of the growing volume of freight traffic on the roads, market-ready autogas systems for trucks would not only help to reduce costs in the freight forwarding industry, but would also be a real benefit for the environment. Finally, vehicles powered purely by autogas emit around 15 % less C02 and up to 80 % less fine particulates and nitrogen oxides than gasoline-powered vehicles. Even if diesel engines cannot yet run in pure LPG mode with the systems for diesel trucks currently in test operation or available on the market, reductions in fine dust emissions of up to 35% have still been demonstrated in mixed operation with autogas and diesel.

A first market-ready autogas diesel system for all commercial vehicles from various manufacturers is offered by the company HEIM technologies gmbh from bippen, germany. The under the name gasotronic marketed system ecocan DIS III regulates the injection of autogas into diesel engines of commercial vehicles (mixed operation). The system, which is completely manufactured in the EU, is certified according to EN 67R01 and has been tested by the German TuV and the Dutch RDW.
For the ecocan DIS III system from gasotronic, all engines are suitable that have a control unit, which is usually available from EURO III onwards. The gasotronic gas system regulates the autogas in the intake manifold without interfering with the actual diesel operation. In the event of malfunctions, the system automatically switches to diesel operation. All system maintenance can be carried out as part of a normal oil change. Only the gas filters need to be replaced. Shortened maintenance intervals as with biodiesel are not necessary.
Of course, the operating range of the converted vehicle must be reduced hummis are ensured by sufficiently large tanks. In the commercial vehicle sector, gas tanks with a volume of 180 to 240 liters are therefore installed, allowing ranges of 1.500 to 2.500 km are possible.

Costs and savings
the retrofit of the ecocan DIS III system from gasotronic costs between 5.500 and 7.000 € plus. 19% ust. In addition, a so-called. machine breakage insurance can be taken out, which can be combined with ca. 490 per year, as the manufacturer’s warranty is voided by the engine intervention. Nevertheless, at the usual mileages for commercial vehicles, considerable savings can be made – even if the vehicle does not run purely on autogas but in mixed mode. According to the manufacturer of the system HEIM technologies gmbh, fuel costs are reduced by 15% to 20% (see HEIM technologies diesel calculator).
Commercial vehicle / truck conversions to autogas are z. B. From our experienced partner THOMAS energieservice gmbh& co. KG carried out near hanover.

4. Boo retrofits with boat gas

When used in motorboats – mostly gasoline-powered outboard engines – the LPG fuel is often called boat gas instead of autogas. The favorable properties of the alternative fuel liquefied petroleum gas (LPG) can basically also be transferred to the application in motorboat / marine operation. The conversion of boat engines takes about two to three days and is currently only carried out by a few specialized companies in Germany. Yards made. Injection engines and older carburetor engines can be converted.
Prices are simply a matter of negotiation and depend on the size of the aggregate and the accessibility of the relevant components. As with the use of LPG in automobiles, the engine is started with gasoline. After a short warm-up period, the gas control unit automatically switches to gas operation. If necessary, it is possible to switch manually between the operating modes.
Boat gas filling stations are still rare. However, the Dortmund-based gas supplier PROGAS in particular is in the process of establishing a comprehensive network of filling stations on the North Sea and Baltic Sea coasts. of course you can find already opened boat gas stations in our autogas station finder.
For tank sizes between 60 and 178 liters, appropriate route planning is therefore required. If there is enough space, you can of course install more than one tank.
the approval of a conversion of a ship engine to marine gas is usually unproblematic in germany. A fixed steel tank and sophisticated safety technology guarantee maximum safety in marine traffic, even in the event of an accident at sea.

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5. TuV approval of autogas conversions

After the installation of the above autogas systems, a certificate of correct installation as well as the leak test according to vdtuv 750, etc. must always be submitted. Required. If you decide to accept an offer from a reputable specialist workshop, you can assume that your vehicle will not be handed over to you until all the necessary papers and certificates have been obtained (exhaust emission report, GSP test certificate and paragraph 19.2 certificate). this is often not the case with cheap autogas conversions abroad. in case of improper installation of the systems, the registration and approval at the registration office can easily be denied.

6. autogas tanks, refueling and connection systems for autogas systems

The most common form of autogas tank is the so-called "cylindrical tank". the cylindrical tank can hold 35 to 180 liters of autogas at a pressure of up to 15 bar, depending on its diameter and length. Due to gas volume changes, autogas tanks may only be used up to max. 80 % fill up. The refueling process is done automatically via a so called. Filling stop valve is switched off as soon as the tank is filled to about 80%. However, this also means that a gas tank with a capacity of z. B. 70 liters can only be filled with 56 liters of autogas, which should be taken into account when choosing the tank size.
For larger vehicles, the cylindrical tank is installed transversely or longitudinally in the trunk. In order to save space in smaller vehicles, it is possible to install a ring-shaped autogas tank, a so-called "spare wheel recess tank", to be installed in the wheel reserve trough. The mobility of the vehicle should then be ensured by the vehicle owner by means of a tire spray or by so-called. runflat tires are ensured. As an alternative to the wheel reserve tank, a so-called "underfloor tank" can be used be mounted in the vehicle floor. Both tank variants – spare wheel recess tank and underfloor tank – are available up to a volume of 70 liters of gas.

Autogas spare wheel tank and cylinder tank without cover (click to enlarge).

The liquid tanks are refueled via a filler neck, which is ideally located behind the tank cap or on the outside of the vehicle (usually on the bumper). Three different connection systems are used worldwide to refuel an autogas vehicle. Depending on the country and type of system, an appropriate adapter is required to use the pump.
A distinction is made between

  • ACME connection ( european adapter ), screw connection)
  • Dish connection ("italy adapter", dish coupling)
  • Bayonet connection ("NL adapter")

Autogas tank filler neck on a golf III (click to enlarge).

For vehicle refueling in germany, austria and switzerland, the ACME connection is relevant. The euroadapter is often included with a conversion at a specialist workshop. So it is possible to refuel everywhere in germany and in european countries. Under the menu item autogas service station network, you can see which adapter you should carry for which country of travel.

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