Vauxhall Workshop Service and Repair Manuals

Z 17 DTH DOHC diesel engine

Model year 2004 will see the introduction of the Z 17 DTH engine for the Corsa-C and Meriva. The Z 17 DTH engine is a further enhancement of the familiar Z 17 DTL engine fitted in the Astra-G.

Inlet side of the Z 17 DTH engine

Exhaust side of the Z 17 DTH engine

The main changes to the Z 17 DTH engine, compared with the Z 17 DTL engine, at a glance:

• Turbocharger with VNT technology
• Denso Common Rail system
• Denso high-pressure pump
• EGR cooler
• Engine timing
• Twin-mass flywheel
• Oil life monitoring

Power curve

1. Torque curve 2. Power curve

Engine-specific data

Turbocharger

The Z 17 DTH engine is fitted with a turbocharger which operates with variable turbine inlet geometry. Thanks to the VNT (variable nozzle turbine), charge pressure control can be adapted depending on load and engine speed by adjusting the guide vanes in the exhaust gas turbine. The guide vanes are adjusted by a vacuum unit actuated by means of a solenoid valve.

Position of the guide vanes at high engine speeds Position of the guide vanes at low engine speeds 1. Exhaust gas turbine 2. Compressor turbine 3. Diaphragm unit - guide vane adjustment 4. Guide vane control mechanism 5. Guide vane

Denso Common Rail system

The Z 17 DTH engine uses a Common Rail system from Denso.

The main features of a Common Rail system are:

• A high-pressure pump with integral delivery pump
• A pressure accumulator (rail) which stores fuel at high pressure
• Injectors (injector nozzles with electronically controlled valves) which accurately meter the injection processes.

Overview of components

1 Injectors 7 High-pressure connection 2 Leak-fuel pipe 8 Fuel feed system 3 Pressure accumulator 9 Metering unit 4 Pressure limiter 10 Fuel temperature sensor 5 High-pressure pump 11 Pressure accumulator sensor 6 Fuel return system 12 Pressurised pipes - injectors

Injector

The injector is a precision-made component with manufacturing tolerances of approx. 3 µm for the needle shaft and high-pressure plunger. When working on these components, the strictest cleanliness must be observed. Even particles of dirt as small as 1/1000 mm will cause malfunctions and may even destroy the injector. The quantity of fuel injected varies from 5 mm ³ at idle speed up to 50 mm ³ at full load. The load-dependent quantity of fuel is injected in a maximum time of 1 ms. The injector is actuated by the engine control unit, with the start of injection and the quantity of fuel injected being determined by the map as a function of load.

Cross sectional diagram of injector
1. Exposed annular area of nozzle needle 2. Valve control plunger 3. Valve control chamber 4. Solenoid valve 5. Fuel return system 6. Electrical connection 7. High-pressure connection 8. Output throttle 9. Input throttle 10. Nozzle needle 11. Nozzle bore

Function of the injectors

The forces required to open and close the nozzle needle cannot be generated with just a solenoid valve. As a result, the nozzle needle is actuated indirectly via a hydraulic force booster system.

I Start of injection When the solenoid valve opens, fuel flows from the valve chamber into the fuel return system. The inlet throttle prevents complete pressure compensation, the pressure in the valve control chamber drops. The excess pressure in the pressure chamber lifts the nozzle needle against the spring force of the nozzle springs and the injection process begins.

II End of injection The solenoid valve is no longer actuated and closes the opening to the fuel return system. Because of the pressure in the valve control chamber, the force acting on the control plunger increases. The nozzle needle is closed as a result and the injection process ends.

Replacing an injector

Each injector has been assigned an individual code (QR code). The QR code contains correction data to compensate for various production tolerances. When replacing an injector, the new injector must be programmed into the engine control unit using TECH 2. This enables the engine control unit to record the necessary correction parameters, thus facilitating precise metering of the injection quantity.

EGR cooler

Like the Z 17 DTL engine, the Z 17 DTH engine has a water-cooled EGR cooler. The cooling performance has been increased by enlarging the volume. By lowering the temperature of the recirculated exhaust gas, it has been possible to reduce the No _x - emissions as well as particulates.

1. Connection - coolant feed 2. Connection - exhaust gas recirculation housing 3. Connection - coolant return 4. Connection - exhaust manifold

Engine timing

The engine control system of the Z 17 engine has been derived from the Y 17 DT engine, which is also fitted with a Denso engine management system.

Oil life monitoring

The Z 17 DTH engine uses the engine oil condition monitoring (oil life monitoring, OLM) system familiar from the Vectra-C. The monitoring function is done by the engine control unit (ECM) and the instrument assembly. Data is displayed by modified OLM software or ECO Service Flex.