SSP427 the BiFuel LPG Drive

Service Training

Self-study Programme 427

The BiFuel LPG Drive

Design and Function

22

S423_889

The self-study programme portrays the design and function of new developments.The contents will not be updated.

For current testing, adjustment and repair instructions, refer to the relevant service literature. Important

Note

For the first time, Volkswagen is offering the Golf 2009 with the 1.6l 75kW MPI engine and LPG drive straight from the factory. LPG is also known as liquid gas or autogas. LPG stands for Liquefied Petroleum Gas. All components that are required for gas operation are fitted on the production line at Volkswagen.

LPG has been in use for decades and is currently the most popular alternative fuel across the world. It is made from a mixture of propane, butane and additives. It burns cleanly and is thus among the latest of energy fuels. In many cities, more and more vehicles are being run on LPG due to rising environmental awareness.

Compared with other fuels, LPG produces considerably fewer exhaust emissions. The same applies to carbon dioxide emissions (CO2), which are associated with climate change. On the whole, the exhaust emissions caused by LPG vehicles are among the lowest that can currently be achieved with combustion engines. LPG fuel is virtually sulphur-free and its combustion produces almost no soot. Hazardous substances like carbon monoxide (CO), hydrocarbons (HC), nitrogen oxide (NOX) and other health- and environment-harming exhaust gas components are considerably less.

33

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

LPG Drive Components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

LPG System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Engine Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Functional Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52

Test Yourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

44

Introduction

LPG (Liquefied Petroleum Gas) is a liquid gas that is used to power combustion engines. It is just as suitable for use as a vehicle fuel like petrol, diesel and natural gas.

LPG is a waste product from natural gas and crude oil refining. It is characterised by a high degree of purity. This prevents aging so LPG can practically be stored indefinitely.

The gas is liquefied under a relatively low excess pressure of approx. 6-10bar and stored in various types of compressed gas container. In this way, it is possible to transport and store large quantities of fuel in a small space. LPG can be used in any location.

The raw material LPGCompared with petrol, LPG has a very high anti-knock index and, depending on the mixture ratio of propane and butane has an octane number of approx. 105 to 115 RON.

The quality requirements for LPG have been standardised across Europe in DIN EN 589 so one will have no problems when driving abroad.

Main components

In principle, LPG is a mixture of hydrocarbons. It is mainly made from a mixture of propane and butane. LPG also contains an odorant. This is added as a precaution since pure LPG is odourless and colourless.

Propane is lighter and liquifies at lower temperatures than butane. Butane, however, has a higher energy proportion per volume unit. The mixing ratio is, dependent on the market, in summer 50:50 (in percentage propane/butane) and in winter 85:15. Deviations from the mixing ratio are possible depending on the supplier. Since propane delivers less energy than butane, the consumption of LPG is slightly higher in winter.

55

Properties of the main components

Propane C3H8 Butane C4H10

Formula: CH3-CH2-CH3 Formula: CH3-CH2-CH2-CH3

Boiling point: -42.1 C Boiling point: -0.5C

Ignition temperature: 470C (petrol 240C)

Ignition temperature: 365C (petrol 240C)

Properties:- Colourless and odourless gas- Heavier than air- Extremely flammable gas

Properties:- Colourless and odourless gas- Heavier than air- Extremely flammable gas

Use as:- Combustion gas for heating and lighting purposes- Propellant in sprays- Balloon gas- Refrigerant in industry

Use as:- Combustion gas in laboratories and households- Low-temperature solvent and extraction agent- Propellant in sprays- Refrigerant in fridges (not for freezing)

Production:Waste product from crude oil refining

Production:Waste product from crude oil refining

The following names for LPG are common across Europe:

- Autogas = Germany- GPL = France Gas de ptrole liqufie, also called GPL-C (GPL-carburant)- GLP = Italy Gas Liquido Propano- GLP = Spain Gases Licuados del Petrleo (GPL Automocin)

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H = hydrogen, C = carbon

66

Introduction

Compared with conventional fuels and other alternative drive energy sources, LPG has an excellent environmental balance as a fuel. Only hydrogen and natural gas achieve comparable results.

Advantages of LPG

Customer advantages Technology and quality advantages

- After sales services from Volkswagen- Full warranty for whole vehicle- Reduction in fuel costs - Trouble-free installation in vehicles with

petrol engines - Constantly growing network of filling

stations, standardised fuel quality across Europe in accordance with DIN EN 589

- High ranges - Very low hazardous emissions - Tax subsidy in Germany until 2018- Easy switch-over from gas to petrol

(even while driving)- Robust engine- Filling connection behind standard filler flap and

not integrated in bumper- Customer has added value when they sell the car

- Mature technology - Special LPG tank - Complete LPG system crash-tested- Optimised exhaust gas and performance thanks to

adapted software- Intake manifold with integrated mount for

gas fuel rail and gas injection valves- LPG wiring harness with VW connectors

77

Economic aspects

LPG has a higher consumption rate amounting to approx. 30 percent more when compared with premium petrol. This is, however, balanced out by the cheaper cost. The consumption per 100 kilometres is thus approx. 7.1 litres with petrol and 9.2 litres with LPG.

A simple example shows whether an LPG vehicle is worthwhile.

Annual kilometres driven 26000km

Period 5 years

Average journey distance 24km

Cost of conversion 2500 euro

Petrol price per litre 1.26 euro

Petrol consumption per 100km 7.10 litres

LPG price per litre 0.54 euro

Autogas consumption per 100km 9.20 litres

Starting petrol per journey 0.10 euro Years

Cost development

0

Euros

3,000

6,000

9,000

12,000

10 2 3 4 5

Example calculation

Annual savings compared with petrol

365.02 euro

Depreciation distance 75,143km

Depreciation period 2.89 years

Evaluation

LPGPetrol

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All figures given here are only examples and are dependent on the respective market.

88

Whenever you want to hit the accelerator in your car, you can do so with petrol, LPG or also natural gas (abbreviation CNG = Compressed Natural Gas).Both LPG and natural gas are sold with the claim that they are a low-pollutant alternative to conventional fuels and drive technologies for cleaner road traffic.

LPG in comparison

Feature LPG Petrol

Composition LPG is made up of propane, butane and an odorant.

Petrol is a complex mixture of over 100 different, mainly light hydrocarbons.

Production LPG is a by-product of crude oil refining (cracking).

Petrol is produced in crude oil refining.

Filling stations LPG filling stations are easy to set up. The LPG tanks are above-ground at the filling station.

Petrol tanks at filling stations need to be built below ground at great expense.

Cost comparison Fuel costs for LPG are lower than for petrol. It is supplied in litres.

Higher fuel prices for petrol and diesel in contrast to LPG.

Carbon dioxide (CO2) emissions

The CO2 emissions from LPG vehicles are around 15% below those from petrol vehicles.

Octane number 105115 RON (depending on butane content)

91 RON for ordinary unleaded petrol95 RON for premium unleaded petrol98 RON for super unleaded petrol

Introduction

99

Feature LPG Petrol

Life LPG is a very pure fuel and thus has unlimited life.

Petrol has a limited life.

Boot volume The LPG tank easily fits in the spare wheel well. As a result, you still have the full boot volume.

Range The original petrol tank remains in the vehicle. This allows a range of approx. 1000km.

Standard/DIN There is a European standard for LPG. DIN EN 589 regulates the quality of LPG.

The composition of petrol varies depending on the oil company.

Taxes The German government has provided a tax concession on LPG until 2018.

Petrol is subject to fuel tax, ecotax and VAT.

1010

Introduction

LPG vehicle populationThe number of privately owned LPG vehicles is constantly growing. This increase shows the increasing acceptance of LPG vehicles among the population.

In 2004, there were initially 15,000 vehicles running on LPG in Germany and just 500 public LPG stations were available to fill them up.

Today, over 300,000 LPG-powered vehicles are on the road in Germany. By 2015, an estimated 1.5 million LPG vehicles will be registered in Germany.Over 5.5 million LPG vehicles are currently in use across the world.

Development of registered LPG vehicles in Germany

2004 2005 2006 2007 2008 2015

50000

100000

150000

200000

250000

15,0

00

65,0

00

125,

00

0

200

,00

0

30

0,0

00 1,

500

,00

0

300000

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1111

Service station networkThe LPG filling station network in Germany has grown constantly over recent years to more than 4,900 public refuelling sites. Further LPG filling stations are planned. Therefore in Germany too as is already the case in other European countries an alternative gas fuel is available in a dense network.In most European countries (in particular in the Netherlands, France, Italy and Poland), a dense network of LPG filling stations has been set up.

Belgium 529

Bosnia-Herzegovina 9

Denmark 16

Germany 4974

Estonia 10

France 1321

Greece 22

United Kingdom 563

Ireland 98

Italy 1981

Croatia 116

Latvia 4

Lithuania 40

Luxembourg 6

Netherlands 1122

Norway 66

Austria 14

Poland 7000

Portugal 94

Rumania 34

Sweden 15

Switzerland 21

Serbia and Montenegro15

Slovenia 14

Slovakia 8

Spain 34

Czech Republic 95

Hungary 256

LPG filling station network in Europe as of May 2009

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Overview of components

LPG Drive Components

Gas filler neck

LPG tank with gas gauge sender G707,pressure relief valve,gas tank valve N495 and automatic fill limiter

All components that are required for gas operation are fitted on the production line. Normal petrol operation remains available as usual.

The LPG system consists of:

- the gas filler neck,- the LPG tank- the selection button with the gas supply gauge and

the fuel selection switch - the vaporiser- the gas filter and - the gas fuel rail with gas injection valves and the

gas rail sensor.

Selection button withgas gauge G706 and

petrol or gas fuel selection switch E395

1313

Gas mode control unit J659

Vaporiser with high pressure valve for gas mode N372

Gas fuel rail with gas injection valves N366-N369and gas rail sensor G401

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Gas filter

Effects upon failure

If one or more components or parts in the LPG system fail, the system switches back to petrol operation. If a fault is reported again upon restarting, the system switches to petrol mode and you should visit a specialist workshop.

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1.6l 75kW engine with 2-valve technology

The basic engine is based on the FlexFuel (E85) engine with engine code CCSA, which, in turn, is based on the technology from the 1.6l 75kW BSE engine. Both engines were used for the first time in the Golf 2004. No mechanical modifications are required to the CCSA petrol engine for operation with LPG. Normal petrol operation is still possible as usual and you can switch to LPG with the selection button in the centre console. The engine reaches an output of 72kW in gas mode.

Technical features

2-valve roller rocker finger Aluminium engine block with ribbed sump Secondary air system Plastic variable intake manifold Modified applications in engine control unit,

adapted to gas operation- Gearbox code JHT as with

BSE engine- The valve train, pistons and piston rings

from the CCSA FlexFuel engine have been used

This engine must not be run on ethanol (E85).

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Torque and power graphs compared

Torq

ue [

Nm

]

Pow

er [

kW]

20

200

40

60

80

100

120

140

160

180

10

100

20

30

40

50

60

70

80

90

1000 3000 5000Engine speed [rpm]

S427_152

7000

Engine code CHGA

Type 4-cylinder in-line engine

Displacement 1595cm3

Bore 81mm

Stroke 77.4mm

Valves per cylinder 2

Compression ratio 10.3:1

Maximum power 75kW at 5600 rpm petrol72KW at 5600 rpm LPG

Maximum torque 148Nm at 3800 rpm petrol144Nm at 3800 rpm LPG

Engine management Simos 7PP

Fuel Premium unleaded RON 95(normal unleaded RON 91 with reduction in performance)LPG

Exhaust gas treatment

Main catalytic converter with Lambda control

Emissions standard EU4

Technical data

Petrol powerGas powerPetrol torqueGas torque

1616

Gas filler neck


The gas filler neck is next to the petrol filler neck behind the tank filler flap and is connected to the LPG tank via an LPG pipe.

The gas filler neck has a check valve. This allows the liquid gas to flow in one direction and stops the liquid gas flowing in the opposite direction.

The check valve opens when the tank is filled under pressure.

Pressure relief valve, check valve

Gas filler neck Cap

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An adapter can be screwed onto the gas filler neck for the different systems used in other countries. The gas nozzle fits onto the adapter when you refuel.

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Filler neck adapterThree different connection systems are currently in use across Europe for filling LPG vehicles. These are the ACME connector, the Dish connector and the Bayonet connector. Depending on the country, you will need the right adapter to use the LPG pumps.

ACME connector Dish connector Bayonet connector

BelgiumGermanyEnglandIreland

LuxembourgPoland

ScotlandSwitzerland

DenmarkFranceGreece

HungaryItaly

AustriaPortugal

Netherlands

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Refuelling procedureA closed system is used for refuelling. Refuelling is just as simple and takes the same time as petrol. The quantity of LPG filled is measured in litres and displayed on the delivery pump like petrol. The maximum filling capacity of the LPG tank is just 80%, so the gas has sufficient volume to expand in summer.

After opening the fuel filler flap, you unscrew the cap from the gas filler neck and screw on the adapter.

Screw nozzle to adapter and pull trigger to lock in place.

Take nozzle

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1919

Press start button and hold down until the tank has been filled.

LPG escapes when you release the filler hose.Keep hands away from the escape holes. There is a risk of frostbite should gas come into contact with skin.

Unscrew nozzle and adapter from gas filler neck and screw cap onto gas filler neck.

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2020

LPG pipesThe liquid gas flows through the LPG pipes from the gas filler neck to the tank and from there to the engine. The LPG system is divided into a high-pressure area and a low-pressure area. The LPG pipes are made from copper piping with a PVC sleeve in the high-pressure area and from special plastic hoses in the low-pressure area.The following LPG pipes are fitted:

All damaged pipes must be replaced during a repair or after an accident.


1. From gas filler neck to tank(high-pressure area)

- Made from copper piping with a PVC sleeve- Pressure from 8-10bar- liquid LPG

2. From tank to vaporiser(high-pressure area)

- Made from copper piping with a PVC sleeve- Pressure from 8-10bar- liquid LPG

3. From vaporiser to gas fuel rail(low-pressure area)

- Made from special plastic hosing- Pressure from 0.1-2bar- gaseous LPG

4. From gas fuel rail to injection valves(low-pressure area)

- Made from special plastic hosing- Pressure from 0.1-2bar- gaseous LPG

2121

LPG tankThe LPG tank is fitted in the spare wheel well. It is made from 3.5mm thick steel.

The LPG tank with crash-optimised mounts and a swirl pot comes with a pressure relief valve, an automatic fill limiter, a gas gauge sender G707 and a gas tank valve N495.

The LPG tank has a capacity of 49 litres. The automatic fill limiter stops the refuelling process when there is 80% LPG in the tank. The filling level is temperature-related and can fluctuate. At an outside temperature of 15C, the LPG tank holds 39 litres.

Pressure relief valve Automatic fill limiter

Gas gauge sender G707

Gas tank valve N495

LPG tank

Swirl pot

Pressure relief valve

Automatic fill limiter


Gas tank valve N495

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Swirl pot

There is a swirl pot in the tank. It guarantees a constant supply of gas in all driving situations, e.g. hill start, hill descents and cornering.

The swirl pot is round and has an opening on top for the pick-up pipe. Furthermore the swirl pot has holes at the bottom and side to allow the liquid gas to get inside the pot.

The snorkel leads to the pressure relief valve in the valve pot.

In collisions, the mounts will not break off, but instead they will deform to absorb the crash energy. The mounts have pre-defined deformation points for this purpose.

Crash-optimised mounts

Mount

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Swirl pot Pick-up pipe for gas tank valve

Tank valve pot

Snorkel

Cover for tank valve pot

Supply line to vaporiser

Supply line from gas filler neck

Holes

2323

Gas tank valve N495

The gas tank valve N495 is fitted in the valve pot and is used to interrupt the gas supply. It is a solenoid valve and is opened by the gas mode control unit J659 during LPG operation. The valve closes automatically and liquid gas no longer flows to the vaporiser when you switch over to petrol mode, turn off the engine, are involved in an accident (crash recognition) or when the voltage supply fails.

How it works:

The valve is pressed into the valve seat by the spring force and thus closes the access to the vaporiser.

Unpowered

Powered

Coil

Spring

Plunger

Valve

To vaporiser

From tank

Coil

Spring

Plunger

Valve

To vaporiser

From tank

The gas mode control unit powers the gas tank valve in LPG mode. The magnetic field of the coil pulls the plunger upwards against the spring force. The access to the vaporiser is now open. If LPG mode is ended, the gas mode control unit immediately shuts off the gas tank valve. The valve is pushed down again by the spring force and the access to the vaporiser is closed.

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Automatic fill limiter

The automatic fill limiter is in the valve pot of the LPG tank. It is used to stop the refuelling process. Refuelling is stopped when the filling level of the tank reaches 80%. The automatic fill limiter is operated mechanically by a float.


Refuelling Filling limit

The filling pressure presses the upper and lower plungers downwards. The upper plunger works as a check valve. The lower plunger opens the outlet holes through which liquid gas flows into the tank. Furthermore the lower plunger has a small hole in the centre through which the liquid gas reaches the tank via the open shut-off valve. When the shut-off valve is open, pressure cannot be built up in the lower valve chamber. Depending on the filling level, the cam disk is turned by a float during the filling procedure. The cam disk operates the shut-off valve.

In the float position corresponding with an 80% filling level, the shut-off valve slips into the cam disk recess and closes the shut-off valve. The liquid gas now builds up pressure in the lower valve chamber. This pressure together with the spring force causes the lower plunger to move upwards. The side outlet holes are then closed. The counter-pressure builds up to the filling pressure, the filling pump switches off and the upper plunger closes the inlet channel due to the spring force.

Filling pressure

Lower plunger

Outlet openings

Cam disk

Shut-off valve

Float

Lower valve chamber

Spring

Upper plunger

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Spring

Inlet channel

2525

Pressure relief valve

The pressure relief valve is fitted in the LPG tank and is located in the valve pot. It prevents the natural gas tank bursting if the pressure rises excessively, for example, because of high temperatures. As soon as the pressure in the tank reaches 27.5bar, the pressure relief valve opens mechanically. The LPG first reaches the valve pot and is vented away from the passenger compartment via breather hoses made from plastic.

Pressure relief valve closed Pressure relief valve open

The valve disk is pressed downwards by the force of the valve spring. The valve is closed. The outlet hole is closed by a red dust cap.

If the pressure in the LPG tank is greater than the force of the valve spring, the pressure relief valve opens due to the valve disk being pushed upwards. The red dust cap is pressed out and the LPG flows into the valve pot. It is vented to atmosphere via breather hoses.

Pressurerelief valve

Breather hoses

Valve disk

Valve spring

Pressure in tankPressure in tank greater than 27.5bar

Escaping LPG

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Dust cap

Outlet aperture

2626



The gas gauge sender G707 is in the tank. The liquid level in the tank is shown1. on a gauge on the tank valve pot and 2. on the fuel gauge (gas gauge G706) integrated in the selection button on the centre console.

1. Display of filling level in valve pot

The float for the gas gauge sender G707 moves in the LPG tank depending on the filling level. This movement is converted into a rotary movement by the gears in the gear mechanism. This also turns the ring magnet in the top of the housing. There is also a ring magnet in the gauge. Depending on the filling level, the two ring magnets have a defined position in relation to each other and create a magnetic field together. This magnetic field influences the position of the needle in the gauge from which you can then read the filling level. The filling level is only shown on the valve pot for safety reasons.

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Float

Gear mechanismGauge

NeedleElectrical connection to gasmode control unit

Top of housing

2727

The driver can read the filling level from the gas gauge G706 integrated in the selection button, which is located on the centre console in the passenger compartment. The gas gauge sender G707 in the tank needs to communicate with the gas mode control unit J659 for this purpose. The gas gauge sender is powered by the gas mode control unit. The magnetic field formed by the two ring magnets then influences the electrical resistance of the conductor. Changing the electrical resistance by applying an external magnetic field is known as a magnetoresistive effect. Different resistances of 0-90 ohm are possible depending on the filling level in the tank. The voltage signal, which is sent by the sender to the gas mode control unit and from there to the gas gauge in the selection button, is thus a measurement for the filling level in the LPG tank.

2. Display of filling level in selection button

Gas mode control unit J659 Gas gauge G706Gas gauge sender G707

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VaporiserThe LPG is converted from liquid to gaseous state in the vaporiser. The vaporiser also has the task of reducing the pressure of the LPG from approx. 10bar to 1bar above the pressure present in the intake manifold. The LPG is expanded in the vaporiser in two stages. The two-stage pressure reduction allows pressure fluctuations to be better compensated for.

Type Two-stage vaporiser with diaphragm

Working pressure 0.95bar to 1.10bar

Max. working pressure

3.5bar

Weight 1450g

Operating nominal throughput

40kg/h

Working temperature From -20C to 120C

Technical data

Technical features

Two-stage pressure reduction High-pressure valve for gas mode with external

connection and integrated filter element Internal coolant circuit for avoiding formation of

moisture and icing

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High-pressurevalve for gasmode N372 Outlet to gas filter

2nd stage from 1.6bar to 1.0bar above intake manifold pressure

1st stage from 3-10bar to 1.6bar

Vacuum connection intake manifold

Coolant, outletCoolant, inlet

Inlet from tank

S427_254

There is an inspection plug on the vaporiser. After 60,000km, this screw needs to be removed to check the vaporiser for impurities. If impurities are found, the filter in the high-pressure valve will need to be replaced. Please refer to the information in ELSA and the maintenance table.

2929

Design

Each stage of the vaporiser consists of an internal chamber, an external chamber and a control chamber containing LPG. The LPG passes from the 1st stage to the 2nd stage via the overflow channel. Also each stage has a valve with a flap and a plunger. The plunger is bolted to the diaphragm. There is a spring in each spring chamber. Atmospheric pressure is present in the spring chamber of the 1st stage. Intake manifold pressure is present in the spring chamber of the 2nd stage. There is a rubber seal between the 1st and 2nd stage that separates the cooling circuit from the LPG.

Outlet to gas filter



Supply line from high-pressure valve for gas mode

Inner chamber

Outer chamber

Control chamber

Spring chamber

Inner chamber

Outer chamber

Control chamber

Spring chamber

Overflow channel

Flap

Flap

PlungerPlunger

Spring

Spring

DiaphragmDiaphragm

Rubber seal S427_252

2nd stage 1st stage

3030


Function

In gas mode, the LPG travels to the vaporiser. To illustrate the processes in the separate stages of the vaporiser, the cross-section of the vaporiser has been greatly simplified.

Supply line from high-pressure valve for gas mode

Inner chamber

Outer chamber

Control chamber

Spring chamber

Overflow channel

Flap

Spring

Diaphragm

Plunger

Flap(open)

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1st stage

The liquid LPG passes through the high-pressure valve for gas mode with a maximum pressure of 10bar to the inner chamber of the 1st stage. The valve flap is open. The liquid LPG passes through the outer chamber to the control chamber of the 1st stage. In this way, the liquid LPG expands and becomes gaseous. The diaphragm of the 1st stage is influenced by the preset spring on the spring chamber side and by the atmospheric pressure present in the spring chamber.

If the gas pressure in the control chamber rises above 1.6bar, the spring will be compressed by the diaphragm. The plunger bolted to the diaphragm operates the flap and the valve closes the supply line from the high-pressure valve for gas mode. No more liquid gas can flow through. The LPG can continue to expand and flow into the inner chamber of the 2nd stage via the overflow channel.

If, as a result, the pressure acting on the diaphragm in the control chamber again falls below 1.6bar, the spring will push the flap open with the plunger and more LPG can flow in. In this way, the pressure of the LPG is reduced from a maximum 10bar to 1.6bar.

Flap(closed)

Spring

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Inner chamber

Outer chamber

Control chamber

Spring chamber

Flap

Diaphragm

Overflow channel

Spring


Plunger

Flap(closed)

Outlet

Spring

Flap(open)

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2nd stage:

In the 2nd stage, the pressure of the LPG, which is already in gaseous form, is relieved and reduced to 1bar above the intake manifold pressure. The LPG passes from the outer chamber of the 1st stage via the overflow channel to the inner chamber of the 2nd stage. The flap of the 2nd stage valve is open during this process. When the gas expands, it passes via the outer chamber to the 2nd stage control chamber. The diaphragm of the 2nd stage is influenced by the preset spring on the spring chamber side and by the intake manifold pressure present in the spring chamber.

If the gas pressure acting on the diaphragm in the control chamber rises 1bar above the intake manifold pressure, the spring will be pressed together by the diaphragm. The plunger bolted to the diaphragm operates the flap, and the valve closes the overflow channel. No more LPG can flow through. The LPG can continue to expand and pass through the outlet to the filter and to the gas injection valves.

If, as a result, the pressure acting on the diaphragm in the control chamber falls again to 1bar above the intake manifold pressure, the spring will push the flap open via the plunger and more LPG can flow in.

3232


Coolant circuit

Design

The coolant circuit is inside the vaporiser. The vaporiser is shown folded open in the middle to illustrate the design. The coolant circuit is connected to the engine coolant system via the two coolant connections. It is split into the 1st and 2nd stage in the vaporiser by the rubber seal. The LPG passes from the 1st stage to the 2nd stage via the two overflow channels.

Function

When the LPG pressure is reduced from 10bar to 1bar above intake manifold pressure, the liquid LPG expands and changes state from liquid to gas. The LPG draws thermal energy from its surroundings so the gas and its surroundings cool down. A refrigerating effect results, which could lead to icing of the vaporiser. The vaporiser is connected to the engine coolant system in front of the heat exchanger via the coolant connections. In this way, the hot coolant passes through the vaporiser. This stops the vaporiser icing.


Rubber seal

2nd stage

1st stage

Coolant overflow channels

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Overflow channel LPGfrom the 1st to 2nd stage

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High-pressure valve for gas mode N372The high pressure valve for gas mode N372 is mounted on the vaporiser and is used to interrupt the gas supply to the vaporiser. A filter is integrated into the high-pressure valve. It is used to filter out any impurities in the liquid LPG in order to protect the sensitive components of the vaporiser. This safety valve works in the same way as the gas tank valve N495.

Not activated Activated

The high pressure valve for gas mode N372 is a solenoid valve and is opened by the gas mode control unit J659 while the vehicle is running on LPG. The valve closes automatically and liquid gas no longer flows to the vaporiser when you switch to petrol mode, turn off the engine, are involved in an accident (crash recognition) or when the voltage supply fails.

The valve is pressed into the valve seat by the spring force and thus closes the access to the vaporiser.

If all system requirements are met for LPG operation, the gas mode control unit operates the high-pressure valve for gas mode. The magnetic field of the coil pulls the plunger against the spring force. The access to the vaporiser is opened. If LPG mode is ended, the gas mode control unit immediately shuts off the high-pressure valve for gas mode. The access to the vaporiser is closed automatically by the spring force.

SpringValve seat

To vaporiser

From tank

Coil

Plunger

SpringValve seat

To vaporiser

From tank

Coil

Plunger

S427_230S427_232

The filter in the high-pressure valve needs to be replaced after 90,000km.

Filter Filter

3434


Gas filterThe gas filter is between the vaporiser and the gas fuel rail.

It is used to protect the gas injection valves and filters fine particles out of the gas.

Gas inlet, from vaporiser

Gas outlet,to gas fuel rail

Filter element

The gas filter needs to be replaced every 30,000km.When fitting the gas filter, make sure that the flow direction arrow corresponds with the flow direction of the gas.

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S427_132

3535

Gas fuel rail

Gas fuel rail

Gas injection valves N366-N369

Gas rail sensor G401

Gas inletGas outlet, hoses to intake manifold

Gas fuel rail

Gas injection valve

Connection for pressureand temperature sensor

Gas inlet

Gas outlet, hoses to intake manifold

Electrical connection

S427_226

S427_214

S427_172

The gas fuel rail is mounted on the engine intake manifold. Four electrically controlled gas injection valves and a gas rail sensor G401, which measures the pressure and temperature of the LPG, are integrated in the gas fuel rail.

The LPG coming from the gas filter flows into the gas fuel rail. The carefully metered gas leaves the gas injection valves through the opening and passes through a plastic pipe to the intake manifold.

The gas injection valves are controlled by the gas mode control unit.

When the gas injection valves are working in gas mode, you will hear clacking noises. In order to counteract the greater noise in gas mode, an insulating mat is fitted under the bonnet.

3636


Gas injection valves N366-N369

Gas inlet

Gas outlet

Electrical connection

S427_142

Before switching automatically from petrol to LPG operation, the function of the gas injection valves is checked once each time the engine is started. This means the gas injection valves are triggered by the control unit and opened briefly. This is a safety measure to clear residue from the gas injection valves and prevent clogging.

S427_080

Actuation Time [ms]

Current [A]

Reaction time: 1.7ms 0.2

Working temperature - 40C to 120C

Max. working pressure 3bar

Technical data

Four gas injection valves N366 - N369 are fitted on the gas fuel rail.

The gas injection valves are controlled by the gas mode control unit J659 in LPG mode with a pulse-width modulated signal.

Technical features

Simple, robust solenoid valve Uses relatively large coils to prevent clogging

with LPG Simple fitting Long life (approx. 290 million cycles)

3737

Function

In LPG mode, the gas injection valves deliver the gaseous LPG into the intake manifold of each cylinder.

Plunger

Gas outlet

Sealing lip

Armature

Pressurespring

Gas inlet

Lowerchamber

Upperchamber

Solenoid

Plunger

Gas outlet

Sealing lip

Armature

Pressurespring

Gas inlet

Lowerchamber

Solenoid

S427_258

S427_260

Not activated

The gas injection valve is not powered. The pressure spring presses the plunger with armature and sealing lip downwards thus closing the gas outlet to the intake manifold. LPG flows into the lower chamber via the gas inlet and into the upper chamber of the gas injection valve via holes in the armature. As a result, the same gas pressure acts on the armature in the upper and lower chamber. This prevents the armature with sealing lip being pressed upwards against the spring force by the pressure in the lower chamber and the gas injection valve opening the gas outlet.

The gas injection valves are electronically controlled by the gas mode control unit. The electrical connection and the solenoid are located in the valve housing. The solenoid generates a magnetic field when it is powered. The armature with sealing lip is pulled against the force of the pressure spring. The LPG from the upper chamber flows via the holes in the armature back into the lower chamber. The gas injection valve opens the gas outlet. The LPG passes through the intake manifold into the combustion chamber.

Activated

3838


Gas fuel rail sensor G401

The gas rail sensor G401 is fitted in the gas fuel rail.

It is used to measure the pressure and temperature of the LPG. The gas temperature and the gas pressure are used to calculate and control the opening times of the gas injection valves.

The gas pressure signal also determines when it is necessary to switch back to petrol mode. Possible reasons for this are:

- An empty LPG tank - A pressure drop in the gas system - A clogged gas filter

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3939

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Display in dash panel insertThe display of the average fuel consumption in the dash panel insert has been adapted to gas mode. This means there can be discrepancies between the range reading and the fuel gauge in petrol mode.

Fuel gauge

S427_170

4040


Gas gauge G706 and petrol or gas fuel selection switch E395

Selection button

Gas mode LED

Petrol mode LED

Gas filling level LEDs

The gas gauge G706 and the petrol or gas fuel selection switch E395 are integrated in a selection button. It is located in the centre console and controls the following functions:

- Petrol/gas fuel selection- Checking gas level in the tank

(fuel gauge)- Indication of malfunctions

(flashing/acoustic signal)

Selection button with gas gauge G706and petrol or gas fuel selection switch E395

Fuel selection

Gas gauge

You can switch over from petrol to gas (or vice versa) with the petrol or gas fuel selection switch E395.

The fuel being used is indicated by the blue ON LED for gas mode or the orange OFF LED for petrol mode being constantly illuminated. If the ON LED flashes quickly, this indicates that the system is waiting to automatically switch over to gas mode during the starting phase (which is always with petrol). The system switches from petrol to LPG mode if the following conditions are met:

- Sufficient LPG in the tank- Coolant temperature greater than 20C- The accelerator pedal is pressed - Engine speed in driving mode greater than

1200 rpm. The row of blue LEDs shows the level of gas in the tank. If the LPG level in the tank is very low, the red reserve LED will be illuminated.

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4141

If the LPG tank is empty, a slow continuous acoustic signal sounds. In addition, the orange OFF LED is illuminated and the blue ON LED flashes slowly. The system has already automatically switched over to petrol mode.To switch off the acoustic signal, the driver needs to press the selection button. Then only the orange LED for petrol mode will be illuminated. The LPG system is in petrol mode. Once the gas tank has been filled again, the driver needs to switch over to LPG mode first with the selection button.

LPG tank empty

Petrol mode only

Malfunctions

A malfunction can have two causes:

1. A temporary faultDuring a brief full-throttle manoeuvre (e.g. overtaking), the gas pressure is no longer sufficient due to the low filling level in the gas tank.

2.A fault in the LPG system (e.g. a faulty gas injection valve).

In both cases, a system fault is recognised and an entry is made in the fault memory of the gas mode control unit.A fast, continuous acoustic signal sounds. In addition, the orange OFF LED is illuminated and the blue ON LED flashes quickly. The control unit automatically switches from gas mode to petrol mode. To switch off the acoustic signal, the driver needs to press the selection button. Then only the orange LED will be illuminated. The LPG system is in petrol mode.

1. If there is a temporary fault, the system switches back to gas mode after you press the selectionbutton and the switch-over conditions have beenmet. For example, this is when: - the engine is running in the lower partial load

range or - the tank has been filled again.

2. If there is a fault in the LPG system due to a faulty component, it is not possible to switch over to LPG mode.

You can switch between gas and petrol mode while driving by pressing the selection button. In this case, the orange LED will be constantly illuminated. Even after restarting, the engine stays in petrol mode until you press the selection button to switch to gas mode.

4242

LPG System

Supply schematics

1 - Gas filler neck2 - Adapter3 - Tank4 - Gas gauge sender G707 5 - Pressure relief valve6 - Automatic fill limiter

Legend

1

7 - Gas tank valve N495 8 - Vaporiser9 - High-pressure valve for gas mode N37210 - Gas filter11 - Gas fuel rail12 - Gas rail sensor G401

Coolant, inlet

Coolant, outlet

Vacuum hose to intake manifold

8

7

6

5

4

3

2

9

4343

13 - Gas injection valves (N366-N369)14 - Gas mode control unit J65915 - Selection button with gas gauge G706 and

petrol or gas fuel selection switch E39516 - Intake manifold

LPG pipe approx. 10bar

LPG pipe approx. 1bar above intake manifold pressure

Vacuum hose

Coolant hose

Sensor signal cable

Actuator signal cable

11

16

13 13 13 13

1514 S427_112

10

12

4444

LPG System

Safety conceptThe safety concept of the LPG system guarantees risk-free operation. The whole natural gas system is installed so that it is protected against damage in the best possible way. All mounting points and materials are designed for maximum safety. The high safety standard has been confirmed by a series of crash tests. The following safety equipment and measures are provided:

1. Check valve in gas filler neck The check valve prevents the gas flowing back while you fill the tank up.

2. LPG tankThe LPG tank is located in the spare wheel well and is thus protected against damage and the elements in the best possible way. It has crash-optimised mounts that do not break in crashes, but instead absorb the deformation. The tank is extremely robust and resistant to heat. The LPG tank made from 3.5mm thick steel meets the highest safety standards. Each individual tank is subjected to a meticulous check and is given a serial number by the manufacturer. All LPG tanks used go through six safety checks and are given a test certificate.

3. Automatic fill limiter in LPG tankThe automatic fill stop when the tank is 80% full allows the LPG to expand as it becomes warm in the tank. Two integrated shut-off valves prevent the gas flowing back while you fill the tank up.

4. Pressure relief valve in LPG tankThe pressure relief valve prevents the natural gas tank bursting if the pressure rises excessively, for example, because of high temperatures. Pipes to the outside stop gas getting inside the vehicle. As soon as the pressure in the tank rises above 27.5bar, it opens mechanically until the pressure in the tank reaches a normal level.

1

4

5

3

2

6

7

8

4545

5. Gas tank valve N495 on LPG tankThe gas tank valve N495 automatically shuts off the gas supply when the engine is not running, in petrol mode as well as in crashes.

6. High-pressure pipes All high-pressure pipes and connecting parts are made from copper and mainly run outside the passenger compartment.

7. High-pressure valve for gas mode N372 on vaporiser

This solenoid valve automatically shuts off the gas supply when the engine is not running, in petrol mode as well as in crashes.

8. Low-pressure pipesFlexible gas pipes on the low-pressure side prevent damage caused by vibrations.

9. Gas injection valves The valves only open when they are operated by the gas mode control unit J659.

The odorants are added to the gas to support the high operating safety of LPG vehicles. This allows you to detect even the smallest leaks in the LPG system with your nose.

8

9

S427_238

4646

System Overview

Sensors

G707 Gas gauge sender

E395 Petrol or gas fuel selection switch

G401 Gas rail sensor

G62 Coolant temperature sender

G28 Engine speed sender

G71 Intake manifold pressure sender

J659 Gas mode control unit

4747

Actuators

N495 Gas tank valve

G706 Gas gauge

N372 High-pressure valve for gas mode

N366 Gas injection valve 1N367 Gas injection valve 2N368 Gas injection valve 3N369 Gas injection valve 4

N30 Injector, cylinder 1N31 Injector, cylinder 2N32 Injector, cylinder 3N33 Injector, cylinder 4

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4848

Engine Management

Control unitsIn addition to the engine control unit J623, the gas mode control unit J659 is required to control the gas mode. There is a connector on the engine wiring harness running to the petrol injectors. The petrol injection signals are interrupted there and forwarded to the gas mode control unit. There the signal is used to calculate the gas injection times. To avoid a fault entry in the engine control unit, the engine control unit receives the expected petrol injector signals via resistors in the gas mode control unit.

Gas mode control unit J659Gas modeEngine control unit J623

Colour code/legend

= earth

= positive

Connector on wiring harnessWires

disconnected

Petrol injector Gas injection valve

S427_282

4949

Gas mode control unit J659

A microprocessor in the gas mode control unit J659 takes over gas regulation to ensure low-emissions and the most efficient combustion in the engine.

Gas sensors, actuators: Gas gauge sender Gas gauge G706 Petrol or gas fuel selection switch

E395 Gas rail sensor Gas tank valve High-pressure valve for gas mode Gas injection valves

Engine sensors: Coolant temperature

sender Engine speed sender Intake manifold pressure

sender

Gas mode control unit J659 Engine control unit J623

Colour code/legend

= input signal

= output signal

= earth

= positiveS427_176

Engine control unit J623

The starting application in engine control unit J623 has been adapted to ensure safe restarting of the vehicle even after the vehicle has been parked in LPG mode.

5050

Functional Diagram

A BatteryE395 Petrol or gas fuel selection switchF Brake light switchG6 Fuel system pressurisation pumpG28 Engine speed senderG39 Lambda probeG40 Hall senderG42 Intake air temperature senderG61 Knock sensor 1G62 Coolant temperature senderG71 Intake manifold pressure senderG79 Accelerator position senderG83 Radiator outlet coolant temperature senderG130 Lambda probe after catalytic converterG185 Accelerator position sender 2G186 Throttle valve drive for electric

throttle

G187 Throttle valve drive angle sender 1 for electric throttle

G188 Throttle valve drive angle sender 2 for electric throttle

G401 Gas rail sensorG476 Clutch position senderG706 Gas gaugeG707 Gas gauge senderJ17 Fuel pump relayJ299 Secondary air pump relayJ329 Terminal 15 voltage supply relayJ338 Throttle valve moduleJ519 Onboard supply control unitJ623 Engine control unitJ659 Gas mode control unit

A

V101

S S S

G28 G185 G79

K

G476

F

SS

J623

G61 G186 G187 G188 J338 G130 G39 G40

G42 G71

G83

J299

S427_200

Terminal 30Terminal 15

5151

Colour code/legend

= input signal

= output signal

= positive

= earth

= powertrain CAN data bus

N30 Injector, cylinder 1N31 Injector, cylinder 2N32 Injector, cylinder 3N33 Injector, cylinder 4N366 Gas injection valve 1N367 Gas injection valve 2N368 Gas injection valve 3N369 Gas injection valve 4N372 High-pressure valve for gas modeN495 Gas tank valveV101 Secondary air pump motor

K Diagnostic connectionS Fuse

1 CAN data bus2 CAN data bus

S

J17

J623

G6 N30 N31 N32 N33

N372 N495 G401

J659

G62

N366 N367 N368 N369

E395 G707G706K

Terminal 30Terminal 15

J329 J519

5252

Service

Please refer to the service information in ELSA!Perform a gas system test after any repair work is performed on the gas system (see Maintenance Manual; book 26.1.)

A pressurised gas tank check is carried out after 10 years as part of the normal MOT. An appropriate test decides whether the LPG tank needs to be replaced.

The gas filter needs to be replaced every 30,000km.

The paper filter in the high-pressure valve for gas mode in the vaporiser needs to be replaced every 90,000km.

The vaporiser needs to be checked for impurities every 60,000km. The inspection bolt on the vaporiser should be removed for this purpose. If impurities are found, the filter in the high-pressure valve will need to be replaced.

5353

Special tools

Description Tool Application

VAS 6227Gas leak detector for natural gas vehicles

For finding leaks in LPG system components

BiFuel software Diagnosis software for gas mode control unit to read and clear fault memory.

USB diagnosis cable For connecting gas mode control unit to the corresponding diagnosis device (VAS 5051B, notebook).

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S427_286

S427_284

5454

Service

Safety in accidentsThe risk of an uncontrollable LPG leak in an accident is extremely small because several safety features would have to fail at the same time. Crash and fire tests have shown that vehicles powered by LPG are no more dangerous than petrol vehicles. If a gas leak is discovered at the accident scene (e.g. there is a smell of gas), the following measures should be taken:

Switch off engine Switch off ignition Clear and cordon off the danger area Do not start the vehicle. If it has to be removed from an enclosed space, push it. Ventilate the vehicle interior (open doors, windows, bonnet and boot) Establish where the gas is concentrated, remember it will collect in areas close to the ground Ensure adequate ventilation, blow away LPG with fan Avoid ignition sources

If the vehicle should catch fire and the LPG tank also be exposed to heat, there is no risk of the tank exploding. At a pressure of approx. 27.5bar inside the tank, the pressure relief valve opens and the LPG is released in a controlled manner. The gas released from the safety valve ignites and burns off in a controlled manner.

If there is a smell of gas, you should not disconnect the battery in case sparks ignite the gas.

Parking in underground car parks (Germany)LPG vehicles are allowed to park in underground car parks. The German garage regulations have taken the high level of safety technology used with LPG into account and allow LPG vehicles full access. All German states have now used this common building regulation as a basis for their local laws.

5555

Test Yourself

1. What is the decisive difference between natural gas and LPG?

a) LPG is basically a propane and butane mixture.

b) LPG is stored in the tank at 200bar.

c) LPG and natural gas are made from what is known as camping gas.

Which answers are correct?

One or several of the answers could be correct.

2. In which vehicles is Volkswagen using LPG?

a) Polo model year 2009.

b) Golf model year 2009.

c) Passat EcoFuel.

3. Autogas is another term for?

a) CNG Compressed Natural Gas.

b) LPG Liquefied Petroleum Gas.

c) LPG Little Pressure Gas

4. Using LPG has benefits for

a) the engine

b) the environment

c) the vehicle owner

5656

Test Yourself

5. What is the boiling point of propane?

a) - 5

b) - 32

c) - 42

6. Which statement is correct?

a) The LPG tank is designed as an underfloor tank.

b) The LPG tank replaces the petrol tank.

c) The LPG tank is fitted in the spare wheel well.

7. At what pressure is LPG stored in the tank?

a) Between 20 and 25bar depending on the outside temperature.

b) At up to 10bar.

c) At the same pressure as natural gas vehicles

8. At what coolant temperature does the engine switch to LPG?

a) 30

b) 25

c) 20

5757

9. In the Golf BiFuel, the engine always starts

a) with LPG.

b) with a mixture of LPG and petrol.

c) with petrol.

10. How is a fault in the gas system indicated?

a) In the selection button, the orange LED flashes quickly, the blue LED is constantly illuminated and a fast intermittent acoustic signal sounds.

b) In the selection button, the blue LED flashes quickly, the orange LED is constantly illuminated and a fast intermittent acoustic signal sounds.

c) In the selection button, the orange LED flashes quickly, the blue LED is constantly illuminated and a constant acoustic signal sounds.

11. After how many kilometres does the gas filter need to be replaced?

a) After one year and 15,000km

b) After 90,000km

c) After 30,000km without time limit

Answers

1. a); 2. b); 3. b); 4. a), b), c); 5 c); 6 c); 7 b); 8 c); 9 c); 10 b); 11 c)

5858

Notes

VOLKSWAGEN AG, WolfsburgAll rights and rights to make technical alterations reserved.000.2812.21.20 Technical status 06.2009

Volkswagen AGAfter Sales QualifizierungService Training VSQ-1Brieffach 1995D-38436 Wolfsburg

This paper was manufactured from pulp that was bleached without the use of chlorine.

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IntroductionLPG Drive ComponentsLPG SystemSystem OverviewEngine ManagementFunctional DiagramServiceTest Yourself

Documents

SSP427 the BiFuel LPG Drive