Audi 80/Avant (B4)

since 1991-1995 release

Repair and operation of the car

Who is interested in operation of the engine, will find the short description of the major parts before we pass to repair work and servicing below.

Pistons, rods and cylinders

In the top third of each piston in the corresponding flutes it is elastic three piston rings are inserted. They, amortiziruya, press on a cylinder wall. Both top piston rings do not pass gases from the combustion chamber down in a case while the lower oil scraper piston ring prevents excessive hit of greasing from a case in the combustion chamber.

Cylinders in which pistons go up and down, are located in the pig-iron block of cylinders of the engine. Internal walls of cylinders are ground by crosswise polishing. Walls of the cylinder should not be absolutely smooth because differently oil, necessary for greasing, will not be able to keep on them. At repair of the engine working surfaces of cylinders can be ground to two times.

Cranked shaft

The problem of a cranked shaft consists in transforming the rectilinear movement of the pistons going in the cylinder up and down to a rotary motion.

The connecting drafts conducting to pistons – rods – affect a cranked shaft, they are located on shatunny necks of a cranked shaft. For prevention of excessive vibration opposite to shatunny necks counterbalances are placed.

To prevent a progibaniye of a cranked shaft in use, it have at the 4-cylinder engine on five, and at 5-cylinder on six bearings – radical necks. Each "knee" located on a rod, thus, on the right and at the left is supported by the bearing. In a different way at the 6-cylinder engine: for reasons of economy of a place here two rods are always located between two radical bearings. Thereby such engine has in total 4 main radical bearings.

Behind in the direction of the movement on cranked to a shaft the disk with a gear wreath for a starter gear wheel is located. It is a flywheel on which coupling is mounted and, thereby, communication with a transmission, or the conducted disk to which the converter of a torque of an automatic transmission is attached is carried out. On other end of a cranked shaft the leading gear wheel of a gear belt and a pulley are attached.

Head of the block of cylinders and camshaft

The head of the block of cylinders in a sense represents the upper bound of combustion chambers.

In the top of a head of the block of cylinders the camshaft is located. Cams it forces valves to open and be closed by (clowns) at certain provisions of pistons. Thereby it defines gas distribution phases. The drive of a camshaft provides a cranked shaft by means of a gear belt.

But the drive of valves occurs not directly through a camshaft. Intermediate instance are so-called dish-shaped pushers. Each such dish-shaped pusher is put on a valve core.

Hydraulic pushers

Hydraulic regulation of a gap in valves is built in already mentioned dish-shaped hydraulic pushers. This device leads to that control of a gap necessary earlier in valves can be not carried out now: the drive of valves works without gaps, the dense prileganiye of the closed valves on a valve saddle and by that faultless tightness is and still provided.

Action of hydraulic pushers

At the closed valve oil from lubricant system of the engine gets through a ring groove to a dish-shaped pusher. After passing of the backpressure valve in a pusher greasing gets to a chamber of a high pressure empty still and completely fills it.

Besides, the spring presses a dish-shaped pusher to a camshaft.

If now the camshaft turns and its eccentric cam presses on a dish-shaped pusher, in a chamber pressure rises. The backpressure valve closes an inlet opening thanks to what oil cannot come to light any more. As oil is not squeezed, rigid connection between a dish-shaped pusher and the cylinder thereby is established. That is the valve can be squeezed out by cam force down.

After closing of the valve because of leak of oil there is a small gap which, however, is immediately counterbalanced by the spring of compression which is squeezing out a dish-shaped pusher up. In the increased volume of a chamber of a high pressure at the open backpressure valve oil again directs. Thereby the hydraulic pusher is ready to the following drive of the valve.

Gear belt

Passing of a gear belt in the 6-cylinder engine

The gear belt set in motion by a cranked shaft is almost silent element of the drive of a camshaft.

Gear belts 4-and the 5-cylinder engine are equipped with so-called thermosensitive tension rollers.

Drive of a gear belt of the 4-cylinder engine

The gear rubber belt reinforced by a steel wire works without wear, besides rubber mix of a gear belt provides dry greasing of pulleys. Along with a camshaft the gear belt puts in action at models with 5-and 6-cylinder engines including the pump of cooling liquid. On models with 4-cylinder engines the belt in addition gives a pomezhutochny shaft which in turn sets the oil pump and the distributor in motion.

Laying of a head of the block of cylinders

Laying between the block of cylinders and a head of the block of cylinders provides isolation from each other of combustion chambers and channels for cooling liquid and oil. Thus it has to resist to extreme fluctuations of temperature and pressure.