Description & Operation: Engine

WARNING: This page is about a different variant/trim than selected.

The 2.0L Zetec 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 is made of cast iron.

The spark plug is installed in the center of the roofshaped 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 are driven by a shared timing belt, and operate four valves per cylinder by means of mechanical valve tappets. One valve spring on each valve is used to close the valve.

Fig 1: Identifying Upper Engine Components

Courtesy of MAZDA MOTORS CORP.

Fig 2: Identifying Cylinder Head Components

Courtesy of MAZDA MOTORS CORP.

Fig 3: Identifying Lower Engine Components (1 Of 2)

Courtesy of MAZDA MOTORS CORP.

Fig 4: Identifying Lower Engine Components (2 Of 2)

Courtesy of MAZDA MOTORS CORP.

Fig 5: Identifying Cylinder Block Components (1 Of 2)

Courtesy of MAZDA MOTORS CORP.

Fig 6: Identifying Cylinder Block Components (2 Of 2)

Courtesy of MAZDA MOTORS CORP.

Fig 7: Identifying Automatic Belt Tensioner

Courtesy of MAZDA MOTORS CORP.

CAUTION: Only tension the timing belt counterclockwise.

An automatic timing belt tensioner makes sure of 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 2.0L Zetec 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.

Fig 8: Identifying Crankshaft, Bearings, Caps & Bolts

Courtesy of MAZDA MOTORS CORP.

The connecting rods are numbered one to four starting at the timing belt end. It is practically impossible to mix up the connecting rod bearing caps and connecting rods since the connecting rod bearing caps are broken away from the connecting rod during production. The fracture profile of a connecting rod bearing cap therefore only fits one of the connecting rods.

Fig 9: View of Lower Crankcase

Courtesy of MAZDA MOTORS CORP.

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

Fig 10: Identifying Lower Crankcase Spacer Shims

Courtesy of MAZDA MOTORS CORP.

Lower crankcase 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 (0.12 in) wide bead of sealer.