BMW S58, Owner'S Handbook Manual

Page: 92 / 102

S58�Engine
11.�Cooling�System
86
Index Explanation
9 Electric�coolant�pump�for�exhaust�turbocharger
10 Exhaust�turbocharger
The�electric�coolant�pump�for�the�turbochargers�is�a�20 W�pump�which�communicates�with�the
DME�via�a�LIN�bus.�The�conventional�coolant�pump�is�driven�via�the�drive�belt�and�cannot�be�used
for�cooling�the�exhaust�turbocharger�after�the�engine�has�shut�down.�This�is�why�there�is�an�electric
coolant�pump�for�this�separate�cooling�circuit.�But�also�during�engine�operation�the�electric�coolant
pump�is�switched�on�taking�into�account�the�following�factors:
• Coolant�temperature�at�the�engine�outlet
• Engine�oil�temperature
• Injected�fuel�quantity
Using�these�values�the�heat�input�into�the�engine�is�calculated.�The�run-on�period�of�the�electric
coolant�pump�can�last�up�to�30 min.�To�improve�the�cooling�effect,�the�electric�fan�also�cuts�in�and�may
run�on�for�up�to�11 min.
11.2.2.�Charge�air�cooling
In�the�S58�engine,�like�in�the�B58TU�engine,�so-called�"indirect"�charge�air�cooling�is�used.�During
the�indirect�charge�air�cooling�the�charge�air�is�cooled�via�a�low-temperature�cooling�circuit.�The�low-
temperature�coolant�circuit�is�then�cooled�again�by�the�atmospheric�airflow�induced�by�vehicle�motion
acting�on�two�water-to-air�heat�exchangers.