Quote:
Originally Posted by Nigel_S
I think 2% drag is still consuming more energy than the fan is consuming even if you take into account the inefficiencies of generating the electricity, however I'm making a lot of guesses to get to that and I'm not sure how much drag use of the fan could save, hence the question...
Thankfully the designers of the car decided to remove that singularity and installed two fans which operate at different temperatures and off different sensors, plus I have a coolant over temperature alarm, plus if the temperature continues to rise the coolant pressure cap will release a cloud of steam and soon after that the low coolant alarm will illuminate. Only if you continue to drive after all that will you cause any damage.
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The 2% is the passive penalty when driving at 40-mph or above,when no fan is necessary.It is just for the friction and turbulence of the heat exchanger and ducting.It represents the 'ideal'.The minimum of which cannot be improved upon.
The electric fan(s) remove the fans parasitic from the engine,and put it on the electrical system.
The 2% + loss is still there,plus any inefficiencies of the alternator drive,the alternator itself,powering the electric motor of a given efficiency,driving a fan of a given efficiency,through a restriction of some static pressure differential which would be dependent upon design.If you don't take advantage of the ram air,it is scientifically impossible to achieve lower than a 2% loss.