"Ross Garrett" > wrote in message
...
>
> "Jan Kalin" > wrote in message
> ...
>> In article >, Ross Garrett wrote:
>>>
>>>"Malt_Hound" > wrote in message
...
>>>
>>>> Which brings me to another thought... why do we need fans that run
>>>> directly off the engine, increasing and decreasing with engine speed,
>>>> when
>>>> in all reality, the biggest need for additional air flow thru the
>>>> radiator
>>>> will be at the lowest engine speed, and the least need for the fan will
>>>> be
>>>> at higher rpm when we are making good speed?
>>>>
>>>> Seems like an intelligently controlled electric fan would be a better
>>>> design, no?
>>>
>>>I am pretty certain the new era of BMW's have electric radiator fans. I
>>>thought I read somewhere that is one of the means they used to lower
>>>engine
>>>loading to increase power yet maintain fuel efficiency (apparently better
>>>battery capabilities mean less load without the fan belt, but also no
>>>increased load for the alternator). The fan and fan speed are driven by
>>>signals from the engine controller. I also think they might have electric
>>>water pumps for the same reason.
>>>
>>>And I know both my E39's had at least some semblance of an electric fan
>>>because it would run long after the engine shut down on hot days when the
>>>AC
>>>had been used.
>>
>> That's the auxillary electrical fan for cooling AC condenser. The main
>> fan
>> is mechanical with a viscous clutch. Check out
>> http://www.realoem.com/bmw/partgrp.d...44&hg=11&fg=35
>> for the main fan (located between the radiator and engine) and
>> http://www.realoem.com/bmw/partgrp.d...44&hg=64&fg=55
>> for the AC fan (located in front of the radiator).
>
> Thanks. I was wrong on the new cars' water pump too. The site clearly
> shows the water pump and alternator run from the same belt.
>

Diesel versions have an extra electric water pump which continues to pump
coolant around the turbocharger bearing and cylinder head area after
shut-down.

Huw