Audi A4

Since 1994 of release

Repair and car operation

The co-ordinated work of separate details

When the engine works, pistons rising and falling in cylinders soak up air. If you completely wring out a gas pedal the engine soaks up air maximum quantity as in this case both throttle заслонки are completely open. It is necessary for an engine neat job, that with soaked up air fuel in an exact proportion mixed up. For definition of a proportion of air and gasoline in a working mix in MPI the weight of soaked up air is used. In MPFI as comparative size the information on pressure serves in an inlet collector and temperature.

Now the management block can submit correct signals for opening and closing of valves of injection. Long opening is provided for big quantity of fuel, short time — at requirement for a fuel small amount.

Start

For start of the cold engine it is necessary more sated, i.e. The working mix rich with fuel as the set of droplets of fuel settles on walls in area всасывания for their way to chambers of combustion and does not participate any more in combustion process. Therefore the fuel share in a toplivno-air mix should be raised.

During management of start of the cold engine duration of injection by valves increases. Such factors as the temperature of a cooling liquid and frequency of rotation of the engine, influence duration of injection. After certain number of turns of the engine the quantity of the fuel necessary for start of the cold engine, slowly decreases and starts to correspond to the standard.

The heated-up engine

After start some time the enriched working mix as still certain quantity of fuel is condensed in area всасывания is necessary to the engine. For this purpose exists послестартовое increase. Depending on temperature some time moves more fuel. The management block receives the necessary information on temperature of the engine from the gauge of temperature of a cooling liquid.

Engine oil, viscous enough at the cold engine, causes the raised internal friction in the car. The raised effort to hold engine turns is necessary. Already mentioned valve of stabilisation of idling is intended for maintenance of giving of this raised quantity of a working mix.

Idling

At closed throttle заслонке through roundabout the channel round throttle заслонки is spent air small amount. This air is fixed by a measuring instrument of a stream of air, or a pressure sensor control and consequently in a working mix for idling it is supplemented with necessary quantity of fuel. As a whole the working mix idling contains more gasoline, than at usual operation that the engine worked exactly and trouble-free in ignition.

The quantity of air, passing the roundabout channel (and, hence, number of turns of the engine idling), is defined by the valve of stabilisation of idling.

Partial loading

At partial loading the engine receives standard quantity of fuel. Thus value is given to minimisation of the expense of fuel.

Accelerations

If the gas pedal the enrichment of a toplivno-air mix necessary for acceleration when the gain of soaked up/oh quantity/weight of air in a second exceeds certain size is caused is suddenly wrung out. As the potentiometer throttle заслонки gives a signal about acceleration. At the cold engine for accelerations it is required большее quantity of fuel. Therefore the management block estimates each impulse of a measuring instrument of a stream of fresh air or a sensor control of pressure and a potentiometer throttle заслонки as a signal about acceleration and increases fuel giving.

Full loading

The potentiometer throttle заслонки shows to the management block that the driver has completely wrung out a gas pedal. To develop the maximum capacity, the engine receives now more enriched working mix (enrichment of a working mix at full loading).

Mode of compulsory idling

At movement downhill with the released pedal of gas it is not necessary to submit fuel to the engine. The car itself slides at the expense of weight or dispersal. On high turns of the engine and position throttle заслонки (from its potentiometer) the management block learns, when there is a mode of compulsory idling, and can save fuel.

Restriction of number of turns

The injection system compares frequency of rotation of the engine at present to the maximum number of turns in 6500 rpm and at their excess simply closes the crane with fuel.