Description And Operation: Engine

The 2.0L Zetec-VCT engine is a four cylinder in-line engine with double overhead camshafts and 16 valves. The 16 valve cylinder head improves volumetric efficiency, particularly at high engine speeds. The 2.0L engine has variable camshaft timing.

The cylinder head is made of aluminum alloy and the cylinder block is made of cast iron.

The spark plug is installed in the center of the roof-shaped combustion chamber to ignite the air/fuel mixture in the combustion chamber. The central location of the spark plug causes the flame front to be evenly spread across the combustion chamber, which also reduces spark knock.

Both camshafts (6250) are driven by a shared timing belt, and operate four valves per cylinder by means of mechanical valve tappets (6500). One valve spring (6513) on each valve is used to close the valve.

An automatic timing belt tensioner ensures the correct timing belt tension. An additional spring-loaded cam provides proper belt tension during operation. The belt tensioner can operate 30 degrees either side of its central position.

The basic adjustment of the belt tensioner can no longer be controlled after the aligning tools and adjusting pin have been taken out (the spring forces from the valve train exert pressure on the timing belt and alter the position of the belt tensioner).

The use of the new variable camshaft timing optimizes the combustion procedure by improving gas exchange in the cylinders. As a result of this exhaust emissions regulations can be met without the use of a pulse air system or exhaust gas recirculation system (EGR system).

The mechanical principles behind variable camshaft timing (VCT) are relatively simple. The valve timing for the opening and closing of the exhaust valves is influenced by a hydraulic cylinder which is riveted to the timing sprocket. This cylinder connects the timing pulley with the camshaft through a hydraulic piston. The hydraulic piston is guided along its axis by the helical gears on the exhaust camshaft and the hydraulic cylinder. The helical gear transfers the up and down motion. As the timing sprocket is fixed in place by the timing belt, the position of the exhaust camshaft is rotated in relation to the timing sprocket, and the exhaust valve timing is therefore adjusted. The hydraulic piston is moved by supplying pressurized engine oil from the engine oil circuit to both pressure chambers of the hydraulic cylinder. The engine management system controls a solenoid valve which in turn supplies the pressurized oil to the pressure chambers.

The return spring ensures the hydraulic piston goes back towards its original position when the engine is switched off.

The VCT unit must be in its original position before the valve timing can be adjusted. Turn the exhaust camshaft in the normal direction of the engine rotation to bring the VCT unit to its original position. When doing this the crankshaft must not be turned.

The oil bores of the oil feed ring and the timing pulley form a labyrinth on three levels. The oil bore of the oil feed ring and the two oil bores (1) on the hydraulic cylinder (one visible) are arranged at 120 degrees to each other. This prevents the hydraulic cylinder from running dry when the engine is switch off. This means that the VCT unit is ready to work shortly after starting the engine.

The lug (2) must be centered between the two oil bores and the mark - if this is not the case, replace the exhaust camshaft timing pulley and the hydraulic cylinder. The lug (2) must locate in the bore when sliding the timing pulley onto the oil feed ring.

The oil feed flange gasket needs to be replaced every time the oil feed flange is disassembled. Proper seating of the gasket ensures that the oil feed flange seals properly and lies properly on the sealing face (incorrect seating can cause tilting).

The 2.0L Zetec - VCT engine is equipped with a glass fiber-reinforced plastic intake manifold. The intake manifold ports are designed so the intake paths are the same length for all the cylinders.

• This gives the following advantages:
  • reduced heat transfer to the injectors, thereby avoiding vapor locks
  • lighter weight
  • reduction of fuel deposits on the intake walls during cold starts
  • less heating of the intake air when the engine is hot

The crankshaft runs on five bearings and has a counterweight for each cylinder. The central main bearing has two bearing half shells which guide the crankshaft along its axis as well as adjusting the end float.

The connecting rods are numbered 1 to 4, starting at the timing belt end. It is almost impossible to mix up the big-end bearing caps and connecting rods, because they are forged as a unit in production and then broken apart. The join between each big-end bearing cap and connecting rod is therefore unique.

The EEC-V module manages the 2.0L Zetec-VCT engine. The module requires a large amount of information about the current operating conditions of the engine and, where appropriate, the automatic transaxle. The EEC-V module obtains this information by means of sensors.

The EEC-V module controls:

• the variable camshaft timing (VCT) unit;
• the fully electronic ignition system (EI);
• the sequential electronic fuel injection system (SFI);
• the air conditioning system together with the cooling system;
• the transaxle control for the CD4E automatic transaxle.

The purpose of the lower crankcase is to reduce engine vibrations. This further reduces the level of noise inside the vehicle. There is a rubber gasket between the lower crankcase and the cylinder block.

Cylinder block cradle spacer shims are used to even out any excessively large gaps between the transaxle and the lower crankcase (see SPECIFICATIONS )

The engine is closed off at the bottom with a pressed steel oil pan which is directly attached to the lower crankcase. It is sealed with a 3 mm wide bead of sealer.