"Dave Plowman (News)" > wrote in message
...
> In article >,
> Malt_Hound > wrote:
>> 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?
>
> Or a progressively driven mechanical one which idles when not needed...
>

The latest hi-tech zenith of efficiency is the Viscotronic fan. This has an
engine management controlled variable speed viscous fan. It is an amazing
piece of kit. I happen to have a bit of experience with an application where
a diagnostic laptop can be linked to the vehicle and the speed of the fan
can be infinitely varied within reason by means of mouse on slider. It so
happens that I have two near identical vehicles except that one has a simple
viscous coupled fan and the other having the latest viscotronic unit and the
reduction of noise from the latter is very noticeable. With the same fan
blades it is probable that this equates to a significant gaining of
horsepower or reduction in fuel consumption.

Huw