Service Training
Self-study Programme 425
EcoFuel Natural Gas Drive with with 1.4 1.4 l 110 110 kW TSI TSI Eng Engin ine e Design and Function
After the successful application of the EcoFuel natural gas drive in the Touran Touran and Caddy, Caddy, this technology is now also being used in i n the Passat, Passat Estate and Touran Touran – for the first time in conjunction with a TSI twincharger engine. From an environmental environmental viewpoint, increased use of this technology is worthwhile worthwhile because the emission of harmful exhaust gases are reduced considerably considerably compared with petrol petrol operation, for example, carbon dioxide (CO2) by 25 %. The Passat TSI TSI EcoFuel with 7-speed dual clutch gearbox therefore produces produces just 119 1 19 g/km of CO 2 in natural gas mode. mode. Furthermore, the exhaust gases produced in natural gas mode do not contain sul phur, phur, soot or fine dust.
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On the following pages, we will wil l introduce you to the design and function of the natural gas drive in the Passat TSI EcoFuel. You will find f ind further information on the topic of natural gas in i n self-study programme no. 262 “Natural gas – an alternative fuel for motor vehicles” and no. 373 “EcoFuel Natural Gas Drive i n Touran Touran und Caddy”.
The self-study programme po rtrays the design and function of new developments! The contents will not be updated.
2
For current testing, adjustment and repair instructions, refer to t he relevant service lit erature. erature.
Important Note
Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 The Passat TSI EcoFuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 The 1.4 l 110 kW TSI twincharger engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Engine Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Changes to engine components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Natural Gas Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 The Passat TSI EcoFuel natural gas drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Engine Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 System overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Engine control unit J623 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Electronic gas pressure regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Dash panel insert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Functional diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Special tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Special features of natural gas vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Test Yourself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
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Introduction The Passat TSI EcoFuel The Passat TSI EcoFuel uses a dual drive. That means it can be driven in both natural gas and petrol mode. In addition to the components for petrol operation, further components for natural gas operation are required. You can see these in the illustration below. You will find more detailed explanations of these components in later sections of this self-study programme.
General vehicle data -
-
Capacity of natural gas tank 21 kg natural gas In natural gas operation, consumption of 4.4 kg natural gas H* every 100 km and a range of approx. 480 km Capacity of petrol tank 31 l petrol In petrol operation, the consumption is 6.8 l petrol every 100 km and the range approx. 460 km
*
Natural gas H (high) has a higher methane content than natural gas L (low). The higher the methane content, the better the natural gas quality and the greater the range.
Electronic gas pressure regulator with high-pressure valve for gas mode N372 and Tank pressure sensor G400
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Gas fuel rail with gas injection valves 1 - 4 N366 - N369 and gas rail sensor G401
4
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Gas shut-off valve relay J908
Gas filler neck with non-return valve (an adapter is required for Italy) Natural gas tanks with tank s hut-off valves 1 - 3 N361 - N363 (tank shut-off valve 3 N363 with n on-return valve)
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Petrol tank
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Dash panel insert with natural gas gauge G411, fuel gauge G1, natural gas mode warning lamp K192 and reserve fuel warning lamp K105
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Introduction The 1.4 l 110 kW TSI twincharger engine This engine has already been used in different vehicle models. However, due to the thermal and mechanical loads in natural gas operation, several components in the engine have been modified. The natural gas functions have been added to the engine management.
Technical features ●
●
● ● ●
One engine control unit for natural gas and petrol operation Homogenous mode (Lambda 1) in both operating modes Turbocharger with waste gate Selectable mechanical supercharger Gas fuel rail with gas rail sensor and gas in jection valves
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The torque/output graph is identical in both operating modes. To achieve this, the supercharger is activated for longer in natural gas mode than in petrol operation. Furthermore the boost pressure is approx. 0.3 bar higher.
Technical data Engine code
CDGA
Type
4-cylinder in-line engine
Displacement
1390 cm3
Bore
76.5 mm
Stroke
75.6 mm
Valves per cylinder
4
Compression ratio
10:1
Maximum output
110 kW at 5500 rpm
Maximum torque
220 Nm at 1500 to 4500 rpm
E ng ine man agemen t
Bosch Motronic ME D 17.1
Fuel
Natural gas H (high) Natural gas L (low) with reduced range Super unleaded RON 95
Exhaust gas treatment
Main catalytic converter, Lambda control
Emissions standard
EU5
Torque and output diagram
) m N ( e u q r o T
) W k ( t u p t u O
Engine speed (rpm) S425_006
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Engine Components Changes to engine components As a fuel, natural gas has a higher anti-knock index compared with petrol in addition to its clean combustion. The octane number for natural gas H can be up to RON 130. This allows an earlier ignition time without combustion knock. The efficiency increases whilst the combustion pressure and combustion temperature in the combustion chamber also increase. However, natural gas is very dry and does not have any lubricating properties like petrol. All of this leads to increased loading on the engine and requires changes to the engine components.
Pistons, piston rings, piston pins, connecting rods The forged pistons are hard anodised in the first and second piston ring grooves. To reduce the surface pressure in the piston hub, the piston pin has been made slightly longer. The top piston ring has a high wear-resistant coating. The upper small end bearing and the small end bush are made from a more wear resistant material.
Piston
Piston rings
Piston pin
S425_008 Connecting rod
Valve timing of camshafts The closing segment of the inlet and exhaust cams has been made less severe. As a result, the valves are closed slightly more slowly and the mechanical load is reduced.
Inlet camshaft
Exhaust camshaft Closing segment
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Valves, valve stem seals, valve guides Valve stem seal
The inlet and exhaust valves are nitrated and reinforced. The valve guides are made from highly wear-resistant material. The valve stem seals have a second sealing lip that forces lubrication of the valve stem in the valve guides. A material with greater wear and corrosion resistance has been chosen for the valve seat rings in the cylinder head.
Valve guide Valve Valve seat S425_012
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Engine Components High-pressure injectors 1 – 4 N30 - N33 In petrol operation, the high-pressure injectors are cooled by the fuel (petrol) that flows through them. There is no cooling in natural gas mode. Since these valves protrude directly into the combustion chamber, unacceptable high temperatures would result.
Aluminium heat sink
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Two measures have therefore been taken: -
Teflon ring with high thermal conductivity
a second Teflon ring with a high thermal conductivity and a heat sink made from aluminium to transfer the heat from the high-pressure injector to the cylinder head.
Oil pump, coolant pump, coolant distributor housing
Thermostat 1 Thermostat 2
The delivery rates of the oil and coolant pumps have been increased – the oil pump has a higher drive speed and the diameter of the coolant pump impeller has been increased from 54 to 60 mm.
Coolant distributor housing
To keep the temperature in the cylinder block down, thermostat 2 in the coolant distributor housing opens at 80 °C.
Duo-centric oil pump Coolant pump S425_064
Oil spray nozzles, oil cooler Oil spray nozzle
Due to the high combustion chamber temperatures in natural gas mode, the piston crowns are heated up greatly. The oil spray nozzles are designed for a higher oil delivery to keep the temperatures as low as possible.
Oil cooler S425_013
Two cooling plates have been added to the oil cooler to increase the cooling performance. Cooling plates
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Turbocharger To obtain a faster turbocharger response, the compressor wheel has been made slightly smaller.
Turbocharger
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Spark plugs Conventional spark plugs would soon wear out due to the greater ignition requirement and the higher spark temperature in natural gas operation. Therefore the materials used in the spark plugs have been changed. The centre electrode is made from a 0.6 mm iridium pin and the earth electrode is made from platinum.
Centre electrode made from iridium
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Earth electrode made from platinum
Exhaust system The exhaust system only stretches to the front natural gas tank. This allows the natural gas tanks and the petrol tank to be made as large as possible. To fulfil EU5, the thickness and composition of the coating in the three-way catalytic converter has been modified for natural gas operation. This is necessary as highly temperature-resistant methane is left after incomplete combustion.
Three-way catalytic converter
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Natural Gas Drive The Passat TSI EcoFuel natural gas drive In the Passat TSI, natural gas mode is mainly used. This means that t he driver does not have the option of switching back and forth between the operating modes. If all conditions for natural gas operation are met, the engine will always start and run in natural gas mode.
Gas filler neck with filter and non-return valve The gas filler neck is behind the tank filler flap on the righthand side of the vehicle above the petrol filler neck. There is a non-return valve and a metal filter on the gas filler neck.
Gas filler neck with filter and non-return valve
Natural gas tanks 1, 2, 3 with a capacity of 21 kg
Mounting bracket
Tank shut-off valves 1 and 2 N361, N362 Protective covers Tank shut-off valve 3 N363 Connecting piece with double clamping device
High-pressure natural gas l ine and connecting pieces The natural gas line is m ade from stainless steel. To ensure that the gas pipes cannot leak, the i ndividual sections are connected with double-clamping devices.
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High-pressure natural gas line
Note that the pressure must be released in the natural gas h igh-pressure pipe before you carry out work on the natural gas system. Please note the instructions in ELSA.
Please note that even if the system has been switched over from natural gas to petrol operation because the gas supply has been exhausted, there will still be a residual amount in the natural gas tanks.
Gas fuel rail with gas rail sensor G401 and gas injection valves N366 - N369
Electronic gas pressure regulator with fuel tank pressure sensor G400 a nd high-pressure valve for gas mode N372 Connections for coolant circuit
Low-pressure natural gas line
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Engine management system System overview Sensors Intake manifold pressure sender G71 with intake air temperature sender G42 Intake manifold pressure sender 3 G583 with intake air temperature sender 3 G520 Charge air pressure sender G31 with intake air temperature sender 2 G299 Engine speed sender G28 Electronic power control fault lamp K132 Hall sender G40 Throttle valve module J338 Throttle valve drive angle sender 1 - 2 for electric throttle G187 - G188
Exhaust emissions warning lamp K83
Regulating flap control unit J808 Regulating flap potentiometer G584
Control unit in dash panel insert J285
Accelerator position sender G79 and accelerator position sender 2 G185 Clutch position sender G476
Brake pedal position sender G100
Fuel pressure sender G247
Knock sensor 1 G61
s 1 e 2 a 1 9 4 d 1 g K l G o m a p r e s u g a m t u g a a a l N g l a g r i n u t n a r N a w
1 5 g n 0 G i 1 e n K g r p u a w m a l g a e l l u e f u e F v r e s e R
Coolant temperature sender G62
Radiator outlet coolant temperature sender G83
Tank pressure sensor G400
Lambda probe G39
Lambda probe after catalytic converter G130
Gas rail sensor G401
Brake servo pressure sensor G294 Additional signals
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Components for natural gas mode
Actuators Fuel pump control unit J538 Fuel system pressurisation pump G6
Engine control unit J623 with ambient pressure sender
Injectors for cylinders 1 - 4 N30 - N33
Ignition coils 1 - 4 with output stage N70, N127, N291, N292 Inlet camshaft control valve 1 N205
N A C n i a r t r e w o P
Turbocharger air recirculation valve N249
Charge pressure control solenoid valve N75
Onboard supply control unit J519 Data bus diagnostic interface J533
Throttle valve module J338 Throttle valve drive for electric t hrottle G186
Regulating flap control unit J808 Regulating flap position control motor V380
Motronic current supply relay J271 Diagnostic connection
Fuel pressure regulating valve N276
Activated charcoal filter solenoid valve 1 N80
Magnetic clutch for supercharger N421
High-pressure valve for gas mode N372
Lambda probe heater Z19
Gas injection valves 1 - 4 N366 - N369
Lambda probe 1 heater after catalytic converter Z29
Gas shut-off valve relay J 908 Tank shut-off valve 1 - 3 N361 - N363
Additional coolant pump relay J496 Coolant circulation pump V50 Additional output signals S425_023
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Engine Management Engine control unit J623 The engine control unit is installed in the centre of the plenum chamber. It manages all functions of petrol and natural gas operation. Lambda = 1 is used in both operating modes.
In basic settings, you switch manually in display group 243 to natural gas mode and in display group 244 to petrol mode. This may be helpful when you are searching for faults. S425_049
Cold start function If the vehicle is started at a coolant temperature below 10 °C, a cold start function for the gas injection valves is activated in petrol mode. This involves adding natural gas (measured at 15 % of the total quantity of fuel required) to the petrol while the high-pressure valve for gas mode is closed. Once the natural gas from the gas fuel rail has been burnt, the gas injection valves are fully powered for approx. 60 seconds. As a result, the temperature in the valves is raised by approx. 35 °C and the gas injection valves will not become clogged. Next the high-pressure valve for gas mode is activated and the pressure is built up a gain in the gas fuel rail. The system then switches over to natural gas mode as soon as possible.
Emergency start strategy If it is not possible to start the engine in one operating mode within 4 to 8 seconds (depending on the coolant temperature), it will be started in the other operating mode. This means, for example: -
If the coolant temperature is 20 °C and no natural gas has been filled up, the vehicle will start in natural gas mode. If this is not possible because of a fault in the natural gas system, it will start in petrol mode.
-
If the coolant temperature is 0 °C, the vehicle will start in petrol mode. If this is not possible because of a fault in the petrol system, it will start in natural gas mode.
On-board diagnose II The on-board diagnosis checks all components and systems relevant to the exhaust ga s while the vehicle is running. It stores the malfunctions and indicates exhaust gas-related errors with the exhaust emissions warning lamp K83.
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Starting strategy The table shows the starting strategy of the 1.4 l 110 kW TSI EcoFuel engine.
Coolant temperature** < 10 °C
Coolant temperature** > 10 °C
Start in petrol mode No prior natural gas fill-up*
With prior natural gas fill-up*
Switch over to natural gas mode Cold start function completed, coolant temperature > 10 °C and time after start > 100 seconds
Start in natural gas mode
Start in petrol mode
Start in petrol mode Until natural gas quality adjustment has been completed
Switch over to natural gas mode after activating the Lambda control, cold start function completed, coolant temperature > 10 °C and time after start > 100 seconds
Switch over to natural gas mode after activating Lambda control, but after 540 seconds at the latest
* Natural gas refuelling Natural gas engines have very good lean-running capabilities, but relatively poor rich-running capabilities. I f natural gas H (rich) is injected with the same opening time as n atural gas L (lean), there could be problems when the engine is started and performance could be poor. To avoid this, natural gas mode cannot be u sed until the Lambda control is activated and the natural gas quality can be recognised. If the engine control unit is informed by the fuel tank pressure sensor G400 that the pressure in the natural gas tanks has increased 30 % since the engine was last run, it will presume that the tank has been filled with natural gas. A natural gas quality adjustment is carried out by the Lambda control and the opening times of the gas injection valves are adjusted. The adjustment is carried out in the middle load/rev range and lasts 60 seconds. The adjustment is interrupted outside the range and the time counter is stopped. The engine will start immediately in natural gas mode only once the adjustment has been completed.
** Coolant temperature At coolant temperatures above 10 °C, the coolant is definitely warm enough to prevent icing of the gas pressure regulator while the natural gas pressure is regulated. Furthermore the valve seats of the gas injection valves are sealed by elastomer seals. At very low temperatures, they can clog and no longer open. That no longer occurs from 10 °C.
15
Engine Management Sensors Fuel tank pressure sensor G400 The fuel tank pressure sensor is screwed into the electronic gas pressure regulator. It is connected to the high-pressure area via a transverse passage and measures the natural gas high pressure.
Tank pressure sensor G400
High-pressure gas inlet from the natural gas tanks
Signal use S425_062
This signal allows the engine control unit to recognise -
the filling level of the natural gas tanks, whether natural gas has been filled up and whether the tank shut-off valves are leak-free. The valves are closed for up to 4 seconds once per driving cycle in a range close to idle for this purpose. The residual gas from the natural gas pipes is burnt and the pressure should fall. If it does not fall, at least one of the valves is leaking.
Gas rail sensor G401
Effects of signal failure If the signal fails, the natural gas gauge shows full. The vehicle continues to drive in natural gas m ode, but will start in petrol mode next time as if the vehicle has been refuelled. If Lambda control is active, the system switches to natural gas mode.
Gas rail sensor G401
The gas rail sensor G401 is bolted onto the front side of the gas fuel rail. It determines the natural gas pressure on the low pressure side.
Signal use The signal is required by the engine control unit -
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to determine whether the natural gas pressure is sufficient for natural gas mode, to regulate the natural gas pressure in the gas fuel rail at 5 - 9 bar and to calculate the opening times of the gas injection valves.
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Effects of signal failure If the gas rail sensor signal fails, the system switches immediately to petrol mode.
Actuators Tank shut-off valves 1 - 3 N361 - N363 Tank shut-off valve
Each natural gas tank has a tank shut-off valve. They seal the natural gas tanks when the ignition is set to “OFF”.
Task The valves are closed when not powered and prevent gas flowing out of the natural gas tanks. In natural gas mode, the solenoid valves are activated together via the gas shut-off valve relay J908 and open the path to the electronic gas pressure regulator. They are opened by the filling pressure while the vehicle is filled up.
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Effects upon failure If one of the valves fails, the vehicle continues to d rive in natural gas mode while there is sufficient natural gas. If a leaking valve is recognised via the fuel tank pressure sensor G400, a fault memory entry is made and the exhaust emissions warning lamp K83 is switched on.
Gas injection valves N366 - N369 The gas injection valves are inserted into the cylinder intake ducts. They are activated by the engine control unit in natural gas mode.
Task S425_021
They have the task of feeding nat ural gas into the intake manifold. Gas injection valve
The opening times of the gas injection valves depend on: -
the engine speed, the engine load, the natural gas quality and the natural gas pressure in the gas fuel rail.
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Effects upon failure If one of the gas injection valves fails, the system switches over to petrol mode.
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Engine Management Electronic gas pressure regulator The electronic gas pressure regulator is mounted on the longitudinal member at the front right of the engine compartment. It regulates the pressure in the low-pressure natural gas system at 5 - 9 bar (absolute). In the previous Touran/Caddy EcoFuel models, it was reduced mechanically to a fixed value of approx. 7 bar (absolute).
S425_025 Electronic gas pressure regulator
The electronic gas pressure regulator is made up of the following components:
Fuel tank pressure sensor G400 This sensor is connected to the high-pressure area via a transverse passage and measures the natural gas high pressure.
1st and 2nd reduction stage
High-pressure gas inlet from the natural gas tanks Coolant connections
Low-pressure gas outlet to engine Tank pressure sensor G400
The first reduction stage reduces the natural gas pressure to 20 bar and the second to 5 - 9 bar.
Mechanical excess pressure valve This valve is screwed into the low-pressure area of the gas pressure regulator and opens at approx. 16 bar. This prevents natural gas flowing into the low-pressure area at a high pressure and causing damage.
Coolant connections When the natural gas pressure is reduced, a large amount of heat is drawn from the s urrounding components. This creates very low temperatures that can lead to icing. To avoid this, the gas pressure regulator is incorporated into the coolant system and heated by the coolant.
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2nd reduction stage high-pressure valve for gas mode N372 1st reduction stage
Mechanical pressure relief valve opens at approx. 16 bar
Breather hole for pressure relief valve
Regulation of natural gas pressure Regulating the natural gas pressure at 5 - 9 bar (absolute) allows the following advantages in the Touran/ Caddy EcoFuel models compared with a fixed pressure of 7 bar (absolute):
Gas is injected at a pressure of 5 bar up to the middle load/rev range. The low pressure allows the vehicle to drive for longer in natural gas m ode. This increases the range by up to 25 km.
Gas is injected at a pressure of 9 bar in the upper load/rev range. This allows more gas to be injected per working cycle at the m aximum opening time of the gas injection valves. This is the only way that a n output of 110 kW or a torque of 220 Nm is possible.
Electronic gas pressure regulator max. gas mass flow at full load 35 kg/h
) r a b ( e r u s s e r p m e t s y S
Mechanical gas pressure regulator max. gas mass flow at full load approx. 27 kg/h
Gas mass flow (kg/h)
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Switch-over between operating modes To ensure that sufficient natural gas continues to flow into the low-pressure natural gas system, the p ressure in the high-pressure natural gas system needs to be higher than the pressure at which it is injected. It needs to be at least 6 bar in the lower load/rev range and at least 15 - 17 bar in the upper load/rev range. If the pressure is lower, it will not be possible to deliver the natural gas as quickly as it is injected and combusted by the engine. If the natural gas p ressure falls below these pressure thresholds in the respective ranges, the system will switch to petrol mode. In the upper load/rev range, the driver can now take his foot off the accelerator and carry on driving in the lower load/rev range. Once the natural gas pressure reaches a sufficient level again (at least 6 bar), the engine control unit switches back to natural gas mode. This switch-back can be carried out twice. If the pressure falls below the threshold again, the car will drive furth er in petrol mode.
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Engine Management 1st reduction stage Reduction of natural gas pressure to approx. 20 bar The gas pressure is reduced in two stages in the gas pressure regulator. The pressure in the first reduction stage is reduced mechanically to approx. 20 bar.
High-pressure gas inlet
The natural gas pressure is less than 20 bar behind the hollow piston.
In-flow of natural gas
Hollow piston
The natural gas flows from the natural gas tanks into the electronic gas pressure regulator via the highpressure gas inlet. There it flows through the two hollow pistons to the right-hand side of the disks. The rising pressure that acts on the disks presses them together with the pistons to the left against the flow of natural gas and against t he spring force.
S425_026 Disk Spring
Tank pressure sensor G400
The natural gas pressure is 20 bar behind the hollow piston. If the pressure on the right-hand side of the disk is approximately 20 bar, the hollow piston rests against the seal and no more gas can be delivered. The natural gas pressure is reduced to approx. 20 bar in the first reduction stage.
The transverse passage leads to the tank pressure sensor. It measures the pressure in the natural gas tanks and recognises whether natural gas has been topped up. Seal
20
Natural ga s pressure after 1st reduction stage approx. 20 bar
Transverse passage to tank pressure sensor G400 High-pressure area
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2nd reduction stage Regulation of natural gas pressure to 5 - 9 bar In the second reduction stage, the natural gas pressure is regulated electronically to 5 - 9 bar by the high-pressure valve for gas mode. The pressure is measured in the low-pressure natural gas system by the gas rail sensor G401.
Transfer from reduction stage 1, approx. 20 bar
The natural gas pressure is approx. 20 bar in front of the high-pressure valve for gas mo de.
Low-pressure area
The first and second reduction stages are connected to each other via a duct . This means that a pressure of approx. 20 bar is applied at the high-pressure valve for gas mode.
Valve ball Valve ball seat
S425_050 Ball guide
Valve needle
High-pressure valve for gas mode N372
Regulation of natural gas pressure at 5 - 9 bar To regulate the natural gas pressure at 5 - 9 bar, the high-pressure valve for n atural gas mode is activated by the engine control unit with a pulse-width modulation signal (PWM signal). The valve needle is shifted and the valve ball moves out of its seat. The gas can now flow until the necessary pressure is reached in the low-pressure natural gas system.
Low-pressure gas outlet to engine
S425_051 In-flow of natural gas
High-pressure valve for gas mode N372
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Engine Management Dash panel insert The following instruments and warning lamps are provided for natural gas mode and petrol mode in the dash panel insert:
● ● ●
Analogue natural gas gauge G411 Analogue fuel gauge G1 Multifunction display
● ●
Natural gas mode warning lamp K192 Reserve fuel warning lamp K105
The natural gas gauge has replaced the coolant temperature gauge. ●
●
The coolant temperature warning lamp K43 is illuminated with ignition “on” and switched off at a coolant temperature of 45 °C. The coolant temperature and coolant shortage warning lamp K28 is illuminated for 3 seconds after ignition “on” and is switched on again from a coolant temperature of 124 °C as a warning.
Multifunction display Coolant temperature and coolant shortage warning K28
Coolant temperature warning lamp K43
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Reserve fuel warning lamp K105
Natural gas mode warning lamp K192 Natural gas gauge G411
22
Fuel gauge G1
Instruments and warning lights in dash panel insert Natural gas gauge G411 (analogue) - The natural gas gauge shows the current natural gas supply in the natural gas tanks. S425_033
Fuel gauge G1 (analogue) - The fuel gauge shows the current petrol supply in the fuel tank.
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Natural gas mode warning lamp K192 - The green warning lamp for natural gas mode indicates that the vehicle is running in natural gas mode. S425_033
Reserve fuel warning lamp K105 - The yellow reserve fuel warning lamp is illuminated only when both fuel types are on at least reserve. That means that the pressure in the natural gas tanks is less than 30 bar and less than 7 l of petrol are in the tank.
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Multifunction display MFD In natural gas mode, the filling levels, ranges and consumption are displayed in the following ways: -
“Please refill natural gas!” “Petrol mode: Please refill natural gas.” “Please refuel.” “Gas start: Please refill petrol.”
Natural gas and petrol are on reserve. When switching to petrol mode, and petrol supply more than reserve When switching to petrol mode, and petrol supply on reserve Vehicle should have started in petrol mode, but this was not possible because the petrol has been used up. Therefore the engine is started in natural gas mode.
A single gong sounds with each of these warnings . Further warnings in natural gas mode include the CNG range (Compressed Natural Gas) in km, the cu rrent consumption at speeds below 3 km/h in kg/h and the current consumption and average consumption at speeds above 3 km/h in kg/100 km. The range is displayed only for the current mode. If the vehicle starts in petrol mode because the coolant temperature is below 10 °C or the vehicle has been refuelled, no remaining range is displayed.
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Engine Management Functional diagram
Legend A G1 G400 G401 G411 J271 J285 J329
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Battery Fuel gauge Tank pressure sensor Gas rail sensor Natural gas gauge Motronic current supply relay Control unit in dash panel insert Terminal 15 voltage supply relay
J519 J533 J6 23 J908 K105 K192 N361 N362
Onboard supply control unit Data bus diagnostic interface Engine cont rol unit Gas shut-off valve relay Reserve fuel warning lamp Natural gas mode warning lamp Valve 1 for tank shut-off Valve 2 for tank shut-off
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N363 N366 N367 N368 N369 N372 S
Valve 3 for tank shut-off Gas injection valve 1 Gas injection valve 2 Gas injection valve 3 Gas injection valve 4 High-pressure valve for gas mode Fuse
Input signal Output signal Positive Earth CAN data bus Diagnosis connector
25
Service Special tools Description
Tool
Application
T50025 Special wrench for tank valve
Wrench for removing and fitting the tan k shut-off valves
S425_058 T50026 Hand wheel
Hand wheel for mechanically closing the tank shut-off valves. S425_059
VAS 6131/15 Mounting set for natural gas tank S425_060
The two rear natural gas tanks are removed together with their mountings. The natural gas tanks a re removed with the scissor-type assembly p latform VAS 6131 A. The mounting set prevents the mountings and natural gas tanks falling during removal.
Special features of natural gas vehicles The pressure in the natural gas tanks should be 200 bar maximum when the temperature of the natural gas tanks and the natural gas is 15 °C. Since the pressure in the natural gas tanks vary depending on the ambient temperature and the compression heat which occurs during refuelling, a higher pressure may be a pplied for filling using a calculation model. After cooling to 15 °C, this pressure should be 200 bar. The natural gas mass filled in kg, not the filling pressure, is decisive for the driver. The natural gas tanks and the natural gas heat up during refuelling. If you then park the vehicle, both will cool down and the pressure in the natural gas tanks will decrease. As a result, t he natural gas gauge may show a lower filling level than before the vehicle was parked. At low temperatures or after refuelling, the engine is always star ted in petrol mode. This can lead to petrol gradually being consumed even though the natural gas supply was never completely used up. There are two natural gas qualities, natural gas H and natural gas L. Natural gas H has a higher methane content and thus a higher heating value, which lea ds to a lower fuel consumption. However, there are also differences within the quality levels that effect the fuel consumption and the range. You can recognise the natural gas quality in display group 243, field 4. The value 1.00 stands for natural gas H with the best quality and 1.29 for natural gas L with the poorest quality.
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Test Yourself Which answers are correct? One or several of the given answers may be correct.
1.
To which gas pressure does the electronic gas pressure regulator in the Passat TSI EcoFuel regulate the low pressure? a) It regulates to a natural gas pressure between 5 and 9 bar (absolute). b) It regulates at a constant 6 bar natural gas pressure. c) It regulates to a natural gas pressure that corresponds with that of the petrol direct injection.
2.
What does the green warning lamp on the natural gas gauge in the dash panel insert indicate? a) The green warning lamp indicates that sufficient gas and petrol is available. b) The green warning lamp indicates that the engine is running in natural gas mode. c) The green warning lamp indicates that there is no fault in the natural gas system.
3.
Which statement about the starting strategy is correct? a) If there is sufficient natural gas in the natural gas tanks, the engine will always be started in natural gas mode. b) The system only switches to natural gas mode when the coolant temperature reaches 60 °C. c) The engine is started in natural gas mode if there is sufficient natural gas pressure, the coolant temperature is more than 10 °C and natural gas has not been refuelled since the last time the engine was run.
4.
How does the engine control unit recognise that the vehicle has been refuelled and what natural gas quality is in the natural gas tanks? a) The gas rail sensor signals that the vehicle has been refuelled and the natural gas quality is recognised via the Lambda control. b) The tank pressure sensor signals that the vehicle has been refuelled and the natural gas quality is recognised via the Lambda control. c) The system does not need to recognise that the vehicle has been refuelled or detect the natural gas quality because the natural gas quality is always the same.
b . 4 ; c . 3 ; b . 2 ; a . 1 : s r e w s n A
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© VOLKSWAGEN AG, Wolfsburg All rights and rights to make technical alterations reserved. 000.2812.19.20 Technical status 03.2009 Volkswagen AG After Sales Qualifizierung Service Training VSQ-1 Brieffach 1995 D - 38436 Wolfsburg
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