Electric superchargers??

["John Fielding" <johnf@domain.elided>]

This was covered about a year or so ago IIRC.  To put things into perspective.  A crank
driven supercharger requires approx. 1 HP to develop an extra 10 HP at the crank, i.e a
total gain of 9 HP.  1 HP = 746 Watts.  Allowing for efficiency conversion from mechanical
to electrical and back again, that would be nearer 850 Watts at best, more likely to
around 1kW/HP. So to gain say 50 HP by supercharging would need an electrical input (from
the battery/alternator combination) of 5 x 850 Watts = 4250 Watts. Convert to 12V from
battery = 354 A!!!!  Not a realistic proposition IMHO.

I proposed an alternative approach in a letter I submitted to a British publication in the
1970's which is to use the excess hydraulic power from a power steering pump to drive a
hydraulic air compressor.  The "powers that be" in that astute publication pointed out
that it would be worse than a crank driven supercharger as the conversion of crank power
to hydraulic pressure would at best be only around 90% efficient.

So you have two alternatives:  Stick with old fashioned crank driven superchargers or use
a more modern approach of turbocharging, which uses energy which would other wise be
wasted, the expanding exhaust gases in the manifold.  Turbocharging power is for free as
the intake pressure comes from the exhaust gases and gives additional engine power.

My 02 cents worth.

John

Durban
South Africa
Alfetta 1.8L turbo - very much alive and kicking, thank you!
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