3 added details on continued coolant circulation
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The W12 engine produced by VW utilizes both mechanical and electric water pumps (underlined with green). According to VW's documentation:

The cooling system of the Audi A8 with W12 engine is made up of the following components:

  • Water pump in cylinder block/crankcase driven mechanically by Poly-V belt
  • Map-controlled electrically operated continued coolant circulation pump -V51 as back-up for mechanical water pump and for continued coolant circulation

There are more details provided on the electric pump:

The electrically driven continued coolant circulation pump -V51 is located in parallel in the large cooling circuit in the return from the radiator. The continued coolant circulation pump -V51 has two functions:

  1. To provide back-up for the mechanically driven coolant pump at low engine speeds and to ensure adequate coolant circulation. -V51 is actuated via the additional coolant pump relay -J496 by engine control unit 1 -J623. Map control is employed to switch in the continued coolant circulation pump -V51 as required. The parameters used for this are the engine speed and the coolant temperature supplied by the coolant-temperature sender -G62.

    Switching levels:

    Cut-in: < 840 rpm and > 108 °C Cut-out: > 3000 rpm or < 106 °C

  2. To circulate the coolant during continued coolant circulationcontinued coolant circulation

Continued coolant circulation is described as well:

Continued coolant circulation

Continued coolant circulation is regulated by engine control unit 1 -J623 in line with a map.

Both the activation condition and the continued coolant circulation time are determined from the following parameters on the basis of an arithmetic model:

  • Coolant temperature (from coolant temperature sender -G62)
  • Engine oil temperature (from oil temperature sender -G8)
  • Ambient temperature (from intake-air temperature sender -G42)

The activation condition and continued coolant circulation period are constantly calculated from the time of starting the engine.

For continued coolant circulation, the pump -V51 and radiator fan -V7 are actuated in parallel.

The maximum continued coolant circulation time is limited to 10 minutes.

The map-controlled engine cooling thermostat -F265 is fully actuated during continued coolant circulation.

Examples of activation condition as a function of ambient and coolant temperature:

  • Ambient temperature 10 °C, Coolant temperature 110 °C
  • Ambient temperature -10 °C, Coolant temperature 115 °C
  • Ambient temperature 40 °C, Coolant temperature 102 °C

W12 Belt Drive

W12 Cooling System

The W12 engine produced by VW utilizes both mechanical and electric water pumps (underlined with green). According to VW's documentation:

The cooling system of the Audi A8 with W12 engine is made up of the following components:

  • Water pump in cylinder block/crankcase driven mechanically by Poly-V belt
  • Map-controlled electrically operated continued coolant circulation pump -V51 as back-up for mechanical water pump and for continued coolant circulation

There are more details provided on the electric pump:

The electrically driven continued coolant circulation pump -V51 is located in parallel in the large cooling circuit in the return from the radiator. The continued coolant circulation pump -V51 has two functions:

  1. To provide back-up for the mechanically driven coolant pump at low engine speeds and to ensure adequate coolant circulation. -V51 is actuated via the additional coolant pump relay -J496 by engine control unit 1 -J623. Map control is employed to switch in the continued coolant circulation pump -V51 as required. The parameters used for this are the engine speed and the coolant temperature supplied by the coolant-temperature sender -G62.

    Switching levels:

    Cut-in: < 840 rpm and > 108 °C Cut-out: > 3000 rpm or < 106 °C

  2. To circulate the coolant during continued coolant circulation

W12 Belt Drive

W12 Cooling System

The W12 engine produced by VW utilizes both mechanical and electric water pumps (underlined with green). According to VW's documentation:

The cooling system of the Audi A8 with W12 engine is made up of the following components:

  • Water pump in cylinder block/crankcase driven mechanically by Poly-V belt
  • Map-controlled electrically operated continued coolant circulation pump -V51 as back-up for mechanical water pump and for continued coolant circulation

There are more details provided on the electric pump:

The electrically driven continued coolant circulation pump -V51 is located in parallel in the large cooling circuit in the return from the radiator. The continued coolant circulation pump -V51 has two functions:

  1. To provide back-up for the mechanically driven coolant pump at low engine speeds and to ensure adequate coolant circulation. -V51 is actuated via the additional coolant pump relay -J496 by engine control unit 1 -J623. Map control is employed to switch in the continued coolant circulation pump -V51 as required. The parameters used for this are the engine speed and the coolant temperature supplied by the coolant-temperature sender -G62.

    Switching levels:

    Cut-in: < 840 rpm and > 108 °C Cut-out: > 3000 rpm or < 106 °C

  2. To circulate the coolant during continued coolant circulation

Continued coolant circulation is described as well:

Continued coolant circulation

Continued coolant circulation is regulated by engine control unit 1 -J623 in line with a map.

Both the activation condition and the continued coolant circulation time are determined from the following parameters on the basis of an arithmetic model:

  • Coolant temperature (from coolant temperature sender -G62)
  • Engine oil temperature (from oil temperature sender -G8)
  • Ambient temperature (from intake-air temperature sender -G42)

The activation condition and continued coolant circulation period are constantly calculated from the time of starting the engine.

For continued coolant circulation, the pump -V51 and radiator fan -V7 are actuated in parallel.

The maximum continued coolant circulation time is limited to 10 minutes.

The map-controlled engine cooling thermostat -F265 is fully actuated during continued coolant circulation.

Examples of activation condition as a function of ambient and coolant temperature:

  • Ambient temperature 10 °C, Coolant temperature 110 °C
  • Ambient temperature -10 °C, Coolant temperature 115 °C
  • Ambient temperature 40 °C, Coolant temperature 102 °C

W12 Belt Drive

W12 Cooling System

2 added documentation references from SSP 267/268
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The W12 engine produced by VW utilizes anboth mechanical and electric water pumppumps (underlined with green). According to VW's documentation:

The cooling system of the Audi A8 with W12 engine is made up of the following components:

  • Water pump in cylinder block/crankcase driven mechanically by Poly-V belt
  • Map-controlled electrically operated continued coolant circulation pump -V51 as back-up for mechanical water pump and for continued coolant circulation

There are more details provided on the electric pump:

The electrically driven continued coolant circulation pump -V51 is located in parallel in the large cooling circuit in the return from the radiator. The continued coolant circulation pump -V51 has two functions:

  1. To provide back-up for the mechanically driven coolant pump at low engine speeds and to ensure adequate coolant circulation. -V51 is actuated via the additional coolant pump relay -J496 by engine control unit 1 -J623. Map control is employed to switch in the continued coolant circulation pump -V51 as required. The parameters used for this are the engine speed and the coolant temperature supplied by the coolant-temperature sender -G62.

    Switching levels:

    Cut-in: < 840 rpm and > 108 °C Cut-out: > 3000 rpm or < 106 °C

  2. To circulate the coolant during continued coolant circulation

W12 Belt Drive

W12 Cooling System

The W12 engine produced by VW utilizes an electric water pump.

The W12 engine produced by VW utilizes both mechanical and electric water pumps (underlined with green). According to VW's documentation:

The cooling system of the Audi A8 with W12 engine is made up of the following components:

  • Water pump in cylinder block/crankcase driven mechanically by Poly-V belt
  • Map-controlled electrically operated continued coolant circulation pump -V51 as back-up for mechanical water pump and for continued coolant circulation

There are more details provided on the electric pump:

The electrically driven continued coolant circulation pump -V51 is located in parallel in the large cooling circuit in the return from the radiator. The continued coolant circulation pump -V51 has two functions:

  1. To provide back-up for the mechanically driven coolant pump at low engine speeds and to ensure adequate coolant circulation. -V51 is actuated via the additional coolant pump relay -J496 by engine control unit 1 -J623. Map control is employed to switch in the continued coolant circulation pump -V51 as required. The parameters used for this are the engine speed and the coolant temperature supplied by the coolant-temperature sender -G62.

    Switching levels:

    Cut-in: < 840 rpm and > 108 °C Cut-out: > 3000 rpm or < 106 °C

  2. To circulate the coolant during continued coolant circulation

W12 Belt Drive

W12 Cooling System

1
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The W12 engine produced by VW utilizes an electric water pump.