Variable Compression, Variable Displacement you decide

[Clint Corbin]

At 10:53 AM 2/18/98 -0600, you wrote:
>It occurs to me, that you could make an electric supercharger (big one not
>the little ones some have now) by putting a generator where you would 
>normally put the supercharger, and then putting an electric motor
>with the blower part elsewhere.  With a bit of control in the electronics
>you would probably be able to boost the low end (over a supercharger,
>way over a turbo) and keep the high end from getting too excessive.  I
>figure that doing things this way would probably boost the cost of
>a blower kit somewhere around 1500 (big enough generator/motor pairs and
>the control stuff get expensive).  It may boost the cost more, but
>it would be alot more adjustable on the fly, even computer controllable,
>ie knock avoidance by reduction in boost.   It would give the computer
>to adjust both the boost and the advance to be optimal for power, or
>fuel efficency.   I know turbodyne makes small electric blowers, but
>as far as I can see they don't produce the necessary pressure at
>volume at wot at higher rpms, so only boost the lower curve, which
>with some engines (that have bad lower curves) would be a bit help,
>but not on larger engines for any kind of racing.
>
>
>			Roger Heflin
> 

Roger,

One BIG problem with this idea: the size of the electric motor driving
the blower!  You are aware that even a "small" blower will suck up
over 50hp at full tilt?  And a big 6-71 can eat over 100hp!  Have you
seen just how large a 100hp electric motor is?  Not pretty and definately
NOT light.  

Of course, there is also the question of efficency.  You will have to have
an alternator that can produce the 50 to 100hp required (yes, I KNOW that
alternators are not normally rated in hp!  Just multiply by 746 to get
watts..)
And, you WILL be loosing some of you power (say, 5 to 10%) to losses in
the alternator.  Then you have your big motor.  It too will loss that same
5 to 
10% (assuming it is a REALLY good motor).  So you are loosing 10 to 20%
right off of the top.  I know that a belt losses some energy (it turns it
to heat),
but nowhere NEAR that much.  Thankfully, we can keep the losses in your
electronic speed control low.  But it will cost a great deal.  

So, could it be done?  Of course.  Would it be anywhere near feasible? Not
hardly.  As alternators and motors get better and better, this will become
more
and more feasible.  Just not for now.

Clint