FW: Re: TORQUATROL UNIT

["Dejong, Paul" <Paul.Dejong@domain.elided>]

> -----Original Message-----
> From:	Dejong, Paul 
> Sent:	Thursday, June 24, 1999 12:59 PM
> To:	'john.h.clayton@domain.elided'
> Subject:	Re: TORQUATROL UNIT
> 
> Dear John,
> 
> The principle of the viscous coupling is that inside the unit a wheel
> (attached to the pulley) is surrounded by a viscous fluid. At low engine
> speed the fluid generates enough friction to turn the unit (and thus the
> fan). At high engine speeds there is not enough friction by which the fan
> will turn slower than the engine rpm. In front of the unit there should be
> a bimetal strip which will engage a lock-up when heated by hot air from
> the radiator by which the fan will turn as fast as the engine rpm thus
> providing extra cooling to the radiator. Even in the most modern and
> technical advanced BMW's of today this system is applied because of its
> big advantage over electric fan's. This advantage is that even at idling
> the fan will provide some airflow through the radiator (and along the
> carburetors) by which it prevents the engine from overheating in traffic
> jams. This results in a more narrow temperature range which is of course
> better for the engine than in case of an electric fan which only engages
> when the engine is already getting hot. The problems with this system are
> that you need a waterpump which keeps the water flowing even at idling
> speed (a twelve vane waterpump in the our case should provide that) and
> secondly that the bimetal strip is not working properly. 
> My Mk1 Stag with its original radiator, though with a converted twelve
> vane pump, never ever has  engaged the lock up and still does not get
> overheated even at one hot day (over 30 degrees) in a traffic jam for an
> hour or so.
> 
> I hope I did not offend anyone with electric fan's but I really think
> highly of the BMW technicians.
> Paul