The 2.0 and 2.4 litre petrol engines are in-line four-cylinder power units with two overhead camshafts (DOHC). The cylinder head is equipped with a continuously variable valve timing (CVVT) system on the inlet side.
Cylinder firing order: 1–3–4–2.
Main components
Cylinder block: made of cast iron.
Cylinder head and water pump housing: made of aluminium alloy.
Crankshaft: forged steel, has five main bearings.
Piston group: the pistons are cast from a special aluminium alloy and are connected to the connecting rods via a floating pin. The piston rings are made of cast iron.
- The upper (first) compression ring has a barrel-shaped working surface.
- The second compression ring is tapered with a chamfer.
- The oil scraper ring is of composite, scraper type with a spring expander.
The combustion chambers in the cylinder head are of the pent-roof type.
Valves: the inlet and exhaust valves are made of heat-resistant steel. The valves are actuated via tappets. The clearance is adjusted using special adjusting shims that have a wear-resistant coating at the point of contact with the camshaft cam.
Timing drive: each cast camshaft rotates in five bearings and is driven by a chain from the crankshaft.
Engine characteristics
Continuously variable valve timing (CVVT) system (for models up to 2009)
The CVVT (Continuously Variable Valve Timing) system provides continuously variable valve timing in accordance with the engine operating mode. This is achieved by rotating the inlet valve camshaft relative to the exhaust valve camshaft within a range of up to 50° (in terms of crankshaft rotation angle).
Diagram of the CVVT actuator operation:
As a result, the moment of the start of opening of the inlet valves and the duration of the valve overlap period (the time when the exhaust valve is not yet closed and the inlet valve is already open) change.
The use of CVVT makes it possible to increase the volumetric efficiency of the cylinders and reduce nitrogen oxide (NOx) emissions due to the effect of internal exhaust gas recirculation (EGR) in all engine operating modes.
From 2009, the continuously variable valve timing (CVVT) system also began to be installed on the exhaust valve camshaft.
Design and operating principle of CVVT
The CVVT actuator is mounted on the camshaft. Its body is connected to the drive sprocket, and the rotor is connected directly to the shaft.
To rotate the shaft, pressurised engine oil is supplied to one side of the rotor vanes through an oil control valve (OCV). At the same time, the opposite cavity of the rotor is connected to the drain. After the required position is reached, both channels are closed, locking the shaft.
Valve timing diagram: EX — exhaust valve, IN1 — inlet valve with late opening, IN2 — inlet valve with early opening.
When the engine is stopped, the maximum retard angle (latest valve opening) is established. To prevent impacts in the mechanism during starting (when the oil pressure is still low), the rotor is locked in the body by a locking pin, which is subsequently released by the oil pressure.
Operation in various modes
- Idle and low load: minimum valve overlap is established to prevent exhaust gases from entering the intake tract and to avoid fuel losses.
- Medium load: early closing of the inlet valves is ensured to improve cylinder filling and increase torque.
- High load, low/medium speed: minimum overlap is established for optimum operation.
- High load, high speed: late closing of the inlet valves is ensured to improve filling at high speeds and increase power.
Results of using the CVVT system
- Torque increases at low and medium speeds.
- Maximum power increases.
- Idle speed is stabilised and fuel economy is improved.
- Engine starting is improved.
Limp-home mode: in the event of a system fault, control is switched off and the camshaft is locked in the position of maximum retard angle.
