Audi 80/Avant (B4)

Since 1991-1995 of release

Repair and car operation

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

Pistons, rods and cylinders

In the top third of each piston in corresponding flutes it is elastic three piston rings are inserted. They, амортизируя, press on a cylinder wall. Both top piston rings do not pass gases from the combustion chamber downwards in картер while bottom маслосъемное the piston ring prevents excessive hit of greasing from картера in the combustion chamber.

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

Cranked shaft

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

Leaders to pistons connecting draughts – rods – operate on a cranked shaft, they are located on шатунных necks of a cranked shaft. For prevention of excessive vibration opposite шатунных necks counterbalances are placed.

To prevent прогибание a cranked shaft while in service, 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 another way at the 6-cylinder engine: from 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 a movement direction 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 and, thereby is mounted, communication with a transmission, or a conducted disk to which the converter of a twisting moment 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 top border of chambers of combustion.

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 positions of pistons. Thereby it defines phases timing. The camshaft drive 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 тарельчатые pushers. Everyone such тарельчатый the pusher is put on a valve core.

Hydraulic pushers

In already mentioned тарельчатые hydraulic pushers hydraulic regulation of a backlash in valves is built in. This device leads to that the control of a backlash necessary earlier in valves can to be spent now: the drive of valves works without backlashes, is and still provided dense прилегание the closed valves on a valve saddle and by that faultless tightness.

Action of hydraulic pushers

At the closed valve oil from lubricant system of the engine gets through a ring groove in тарельчатый a pusher. After passage of the return valve to a pusher greasing gets in empty still the chamber of a high pressure and completely fills it.

Besides, the spring presses тарельчатый a pusher to a camshaft.

If the camshaft and its eccentric cam now turns presses on тарельчатый a pusher in the chamber pressure rises. The return valve closes an inlet aperture thanks to what oil cannot come to light any more. As oil несжимаемо rigid connection between тарельчатым a pusher and the cylinder thereby is established. That is the valve can be squeezed out downwards force of a cam.

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

Gear belt

Passage of a gear belt to the 6-cylinder engine

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

Gear belts 4 and the 5-cylinder engine are equipped by 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 deterioration, besides the 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 a cooling liquid. On models with 4-cylinder engines the belt in addition results помежуточный a shaft which in turn actuates the oil pump and the distributor.

Lining of a head of the block of cylinders

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