Electrical Supercharger

[avos at cochlear.com.au]

     I was'nt involved in the previous discussions on this subject but I 
     have often wondered about electrical supercharging. The main problem I 
     have always wondered about is the feasibilty of producing an 
     electrical pump that does not consume more current than the alternator 
     produces. Unfortunately I am not aware of the amount of power required 
     for such an electrilcal pump - Does any one have an idea how much 
     electrical power would be required? I hear that a super-charger takes 
     several kW out of an engine, so I can't imagine that an electrical 
     pump would require any less power????? This would mean the electrical 
     pump would need  hundreds of amps of current at 12V. A second battery 
     an alternator perhaps??
     
     In the interest of efficiency though, the turbo is still the way to go 
     since kinetic/thermal energy in the exhaust is essentially free 
     anyway. Perhaps the problem of lag in turbos may be solved by 
     producing a turbo that has an electrical propulsion when not enough 
     exhaust gases are being produced. This would be efficient, as at low 
     revs the engine does not consume as much gas, so the electrical 
     propulsion could be relatively low power, but at higher revs when 
     higher intake flows are required, the exhaust propulsion will be up to 
     the task.
     
     Just an idea!!
     
     Adrian


______________________________ Reply Separator _________________________________
Subject: Electrical Supercharger
Author:  diy_efi at coulomb.eng.ohio-state.edu at INTERNET
Date:    09/5/97 13:55


     
 I noticed a while back (over a year ago) there was a discussion about
electrically powered superchargers. I was wondering if anyone actually 
followed through on plans and tried it. To me, there are several advantages 
to electrical power over the traditional crankshaft power:
     
 1. Cost (electric motors are less than blowers and don't strain engine as
much)
 2. Placement -- the placement isn't dictated by crank positioning. 
 3. Ease of installation -- no need to completely tear apart front of
engine
 4. Adjustability of boost -- a simple 2-d rpm and boost mapping system can
be made
     
 However, I was thinking of the extra energy losses by using an electrical
blower. In a regular system there are only two possibilities for energy 
loss:
     
 1. Crankshaft attachment scheme / gearing (if any) 
 2. Impeller / screw losses
     
 An electrical system incurs three energy losses though:
     
 1. Alternator inefficiency
 2. Electric motor inefficiency
 3. impeller / screw losses
     
 I was wondering whether or not a system could be developed to produce 3psi
or so. That would be enough to satisfy my performance cravings for now. 
About how much power could one expect from just a couple of pounds of 
boost? Remember, the blower wouldn't consume any extra power off the engine 
if using the stock alternator. On my car, a BMW 325is (relatively little 
displacement of 2.5liters) a regular supercharger kit costs around $6K! As 
you can imagine, I would be very willing to accept a fraction of the power 
boost for a small fraction of that cost. Also, designing the system myself 
would be fun. 
     
=-=-=-=-=-=-=-=-=-=-=
Steve Meade
smeade at deltanet.com