bmw-digest RE: Electric Superchargers

[GreggOtt@xxxxxxx]

If the electrical power is coming from the alternator, there will be a net
loss of HP to the drive train.  

First of all, if everything was 100% efficient, it would take exactly 5 HP of
alternator load to get 5 extra  BHP.  This is because there is no such thing
as a free lunch in the energy world (1st law of thermodynamics - conservation
of energy).

Second, there is no such thing as 100% efficiency.  The alternator is probably
about 75% efficient at best.  Additionally, the blower motor is not even close
to 100% efficient.  Lastly,  engine itself has a thermal efficiency of about
25%.  Do the math.

So, if you ARE getting extra horsepower, it is because you are fully loading
the alternator and draining the battery every time you run the blower  --
definitely bad for the charging system. 

Gregg

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