Engine: Description and Operation

Engine





The name of this engine is 2.0L Zetec-VCT. The suffix VCT stands for variable camshaft timing. The transversely mounted engine is tilted forwards by eight degrees. As a result, a considerable space saving has been made in the engine compartment.

Location of serial number on cylinder block:

Location of serial number on cylinder block

Design of the 2.0L engine
Basic concept

Timing Belt Center Cover/Engine Front Mounting Bracket:

The 2.0L 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 cylinder head is made of aluminum alloy and the cylinder block of cast iron.

Timing belt center cover/engine front mounting bracket
The new timing belt cover has a vertical strengthening rib for additional reinforcement. As a result of this, the timing belt center cover (and therefore the front mounting) has to be removed in order to install a new timing belt.

Cylinder head
Combustion chamber
The spark plug is installed in the center of the fuel/air roof- shaped combustion chamber to ignite the 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 the spark knock.

Valve train (vehicles build up to 06/1999)
Both camshafts are driven by a shared timing belt, and operate four valves per cylinder by means of adjustable tappets. One spring on each valve is used to close the valve.
The spring on the exhaust valve is marked with a blue paint mark, and the spring on the intake valve with a red one. The adjusting shims in the valve tappets can be changed to correct the valve clearance. These are available in 52 different thicknesses. The shim thickness is stamped on the back of the shim in hundredths of a millimeter (Example: the number 222 means 2.22 mm). Because of space limitations in the cylinder head the camshafts have to be removed before the adjusting shims can be renewed. This means that a high degree of accuracy is required during adjusting to avoid repeated removal and installation of the camshafts. The camshaft cams run concentrically on the valve tappets. At engine speeds of above about 3000 rpm this causes the tappets to rotate, and they in turn transfer the rotation to the valves. This valve rotation is required because it produces an even valve seating and prevents the valves from wearing in a certain position which could cause them to leak.











Engine Component View

Timing belt tensioner

CAUTION: Only tension the timing belt counterclockwise.

An automatic timing belt tensioner ensures the correct timing belt tension. When fitting a new timing belt move the tensioner into its basic position (pointer (3) and mark (2) line up). This basic adjustment is carried out by means of a cam (4). An additional spring-loaded cam provides correct belt tension during operation. The belt tensioner can operate 30 degrees either side of its central position.

NOTE: The timing belt must not be re-tensioned in case the operating range of the tensioner is exceeded. The basic adjustment of the belt tensioner only applies to new timing belts. Re-tensioning the belt can cause it to tear or flap.

CAUTION: Always install a new timing belt after slackening/removing it.

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).








Automatic belt tensioner

Variable Camshaft Timing (VCT)
General
The use of the new variable camshaft timing optimizes the combustion procedure by improving gas exchange in the cylinders. As a result of this the exhaust emissions regulations can be met without the use of a pulse air system or an Exhaust Gas Recirculation (EGR) system.

Mechanical operation








Mechanical design of the VCT unit
The mechanical principles behind Variable Camshaft Timing (VCT) are relatively simple. The valve timing for opening and closing of the exhaust valves is influenced by a hydraulic cylinder (3) which is riveted to the pulley (1). This cylinder connects the pulley (1) with the camshaft (8) through a hydraulic piston (4) and inner gear bush (6). The hydraulic piston is guided along its axis by the helical gears (6,7) on the exhaust camshaft and the hydraulic cylinder. The helical gear transfers the up and down motion of the hydraulic piston into a rotary motion. As the pulley is fixed in place by the timing belt, the position of the exhaust camshaft is rotated in relation to the pulley, 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 (3) ensures that the hydraulic piston goes returns towards its original position when the engine is switched off.
Emergency mode:
- If oil pressure is to low, the VCT will be regulated to the "END-STOP" position.
- In cause of an electrical error, the solenoid will regulate to the "END-STOP" position.

Hydraulic operation

















VCT unit in Original Position and at maximum extension
The VCT unit is supplied with engine oil (3) from the engine oil circuit and controlled by the engine management system. The engine management system regulates the solenoid valve (2) through a Pulse Width Modulation (PWM) from 0-100%.
With rising current (0-1A) the displacement of the control piston (4) in relation to the return spring (6) increases, and vice versa. As a result of this motion the control edges and return bores (5) of the control piston open and close the oil flow to and from the two pressure chambers (11,12) of the hydraulic cylinder (9).








When the engine is switched off the return spring returns the control piston back to its original position. At the same time the return bores in the front pressure chamber (12) are opened, which allows the return spring (11) to slide back the piston in the hydraulic cylinder towards its original position.
The hydraulic unit can be infinitely adjusted in the hydraulic cylinder. However, the control piston can only move into three positions.

Working on the VCT unit
When the engine is switched off the VCT unit is nonpressurised and therefore has no function. However, the hydraulic piston usually only returns right back to the original position if the VCT unit has been removed or the engine management system caused this to happen just before the engine was switched off. A complete return to the original position is prevented by friction on the cams and the spring forces due to the valve springs.
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 engine rotation to bring the VCT unit to its original position. When doing this the crankshaft must not be turned.

Installation position - oil feed ring/camshaft pulley

Installation Position-Oil Feed Ring/Camshaft:

The triple oil bore of the oil feed ring and the camshaft pulley form a labyrinth on three levels. The oil bores of the oil feed ring and the two triple 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 switched off. This means that the VCT unit is ready to work shortly after starting the engine.
The lug (2) must be centered between the three oil bores (1) and the mark. If this is not the case install a new exhaust camshaft timing pulley and a new hydraulic cylinder. The lug (2) must locate in the bore when sliding the timing pulley onto the oil feed ring.

Oil feed flange gasket (3 x O-ring seal)

Oil Feed Flange Gasket (3 X O-Ring Seal):

NOTE: Use a thumb to press the positioning pins on the gas x O-ring seals into the oil teed flange in the positions shown.

A new oil teed flange gasket needs to be installed every time the oil feed flange is disassembled. Correct seating of the gasket make sure the; the oil teed flange seals correctly and lies correctly on the sealing face (incorrect seating can cause tilting).

Components Attached to Cylinder Head
Intake manifold
The 2.0L engine is equipped with a glass fiber reinforced plastic intake manifold. The intake manifold ports are designed so that 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 pipe walls during cold starts
- less heating of the intake air when the engine is hot.














Components Attached to Intake Manifold:

Cylinder Block
Crankshaft
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.











Crankshaft bearings

Connecting rod bearings
The connecting rods are numbered 1 to 4, starting at the timing connecting rod. 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 connecting rod bearing cap and connecting rod is therefore unique.

Lower crankcase and oil pan
Lower crankcase seal gas

View Of Lower Crankcase:

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.

Lower crankcase spacer shims

Lower Crankcase Spacer Shims:

Lower crankcase spacer shims are used to even out any excessively large gaps between the transaxle and the lower crankcase (see Specifications).

Oil pan
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.

Engine Management
EEC V module
The EEC V module manages the 2.0L engine. The module requires a large amount of information about the current operating conditions of the engine and, where appropriate, the automatic transaxle (CD4E). 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 (EI) system
- the Sequential Multiport Fuel Injection (SFI) system
- the Air Conditioning (A/C) system together with the cooling system the transaxle control for the CD4E automatic transaxle.