Introduction
The Opel GT is equipped with a 2.0 litre Z 20 NHH, four-cylinder turbocharged petrol engine as standard.
View of Engine (Exhaust Side)
The illustration shows the front and exhaust side of the Z 20 NHH engine.
View of Engine (Intake Side)
The illustration shows rear and intake side of the Z 20 NHH engine.
View of Engine in Engine Compartment
| 1. | Throttle body | 7. | Mass air flow meter and air temperature sensor | |
|---|---|---|---|---|
| 2. | Dipstick | 8. | Intercooler air inlet duct | |
| 3. | Intake air pressure and temperature sensor | 9. | Turbocharger | |
| 4. | Vacuum hose connection | 10. | Acoustic engine cover | |
| 5. | Intercooler air outlet duct | 11. | Oil filler cap | |
| 6. | Charge air cleaner assembly |
Torque and Output Curves
| A. | Torque curve |
|---|---|
| B. | Output curve |
General Description – Mechanical
The cylinder block is made of cast aluminium, with four cast iron cylinder liners that are pressed in and arranged in-line. The cylinder block comprises an upper and lower crankcase for a rigid construction with reduced noise and vibration. The cylinder block houses five crankshaft bearings, with No. 2 bearing being the thrust bearing.
The crankshaft is equipped with a reluctor wheel that has 58 teeth and a reference gap. Each tooth on the reluctor wheel is spaced 6 degrees apart with a 12-degree space for the reference gap. The magnetic pulse from the reference gap (sync pulse) is sensed by the crankshaft position sensor and used, via the engine control unit (ECU), to synchronize the coil firing sequence with the crankshaft position. The other teeth provide cylinder location during crankshaft revolution.
Each connecting rod and piston assembly has a floating piston pin. The pistons are made of cast aluminium, with low tension piston rings to reduce friction. The top compression ring is made of ductile iron with a molybdenum facing and phosphate coated sides. The second compression ring is made of grey iron. The oil ring is a 3-piece spring construction with chromium plating.
The oil pan is made of cast aluminium and includes an attachment to the transmission to provide additional structural support.
The cylinder block houses two balance shafts located one each side of the crankcase at the bottom of the cylinder bores. The balance shafts help to reduce vibration and are driven by means of a single roller chain that also drives the water pump. The chain is tensioned by means of a hydraulic tensioner that is supplied with hydraulic pressure from the oil pump.
The cylinder head is an aluminium casting. The valve guides and valve seat insets are made of pressed-in powdered metal. The fuel injection nozzle is located below the intake port. The cylinder head houses the camshaft journals and camshaft caps.
There are two intake valves and two exhaust valves per cylinder. The intake valves are equipped with rotators that are located at the bottom of the valve spring. Positive valve stem seals are installed on all valves.
The engine has two cast iron camshafts, one for the intake valves, the other for the exhaust valves.
The valve train uses a roller finger follower acted on by a hydraulic tappet adjuster to reduce friction and noise.
The camshafts are driven by a single-row roller chain. A tensioner and guide are installed on the untensioned side of the chain to control chain motion and noise.
The exhaust manifold is made of cast iron. The intake manifold incorporates a distribution and control system for positive crankcase ventilation.
Lubricating oil is supplied under pressure to the crankshaft, connecting rods, balance shaft assembly, camshaft bearing surfaces, valve lifters and timing chain hydraulic tensioner. All other moving parts are lubricated by gravity flow or splash. The oil pump is located within the engine front cover and is driven by the crankshaft. The oil filter is a disposable cartridge type and is housed in a casting that is integrated with the engine block.
Engine Management System
The ECU is located in the engine compartment adjacent to the engine bulkhead on the left hand side and controls the following:
- Fuel injection system
- Ignition system
- Emission control systems
- Air conditioning and fan systems
- Throttle actuation control system
- On-board diagnostics
The ECU constantly monitors the information from various sensors and other inputs, and controls the systems that affect vehicle performance and emissions. The ECU also performs diagnostic tests on various parts of the system. The ECU can recognise operational problems and alert the driver via a telltale on the instrument assembly. When the ECU detects a malfunction, the ECU stores a diagnostic trouble code (DTC).
The ECU receives the following input signals from dedicated sensors:
- Manifold absolute pressure (MAP) sensor
- Intake air pressure and temperature sensor
- Fuel tank pressure sensor
- Camshaft position (intake) sensor
- Camshaft position (exhaust) sensor
- Engine coolant temperature sensor
- Accelerator pedal position sensor
- Crankshaft position sensor
- Air conditioning refrigerant pressure sensor
- Brake booster vacuum sensor
- Intake air temperature/mass airflow sensor
- Heated oxygen sensors
- Knock sensor
- Fuel rail pressure sensor
Fuel Injection System
The high pressure fuel pump receives low pressure fuel from the fuel pump module inside the fuel tank. The high pressure fuel pump is driven by a three lobe cam on the intake camshaft. The pump is equipped with a fuel rail pressure regulator and a pressure relief valve. The fuel rail pressure regulator controls the inlet valve of the pump.
The high pressure fuel pump, fuel rail pressure, fuel injection timing and injection duration are controlled by the ECU.
The throttle assembly contains the throttle blade, actuator motor and two throttle position sensors.