Max Dillon wrote:
So, let me get this straight. One belt drives the alternator. That alternator
provides the electricity to run the electric motors, which turn the oil pump,
water pump, compressor and power steering pump. And this saves horse power,
converting torque into electricity and then back into torque again? The number
of belts has stayed the same, the number of electric motors has increased by
four, so I don't think any weight has been saved.
I can see how selectively and temporarily removing loads when maximum
acceleration is called for can make more power available to turn the driving
wheels, but I don't see how this increases fuel economy.
1. Let us assume that the engineers want at least 50psi oil pressure at cruising
speed, and that takes about 1/2 gpm. Let us also assume that a mechanical drive
oil pump puts out 1.5gpm at that engine speed, and the pressure relief valve is
set for 90psi. So the mechanical pump has to pump 1.5gpm at 90psi, while the
electric one pumps .5gpm at 50psi. There's room for a large percentage savings
in pump power.
2. A mechanical drive water pump has to pump enough water to cool under maximum
cooling needs at all times, the thermostat controls how much actually goes
through the engine. With our electric PWM drive water pump, we get rid of the
thermostat and pump just enough water to cool the engine. I bet the savings are
over 90% in the winter, and substantial in the summer except when you're
climbing a hill with the A/C on or towing a heavy load.
3. A/C: by far the most efficient home A/C units are the 'inverter drive'
compressors, they lose 5-10% converting AC line current to DC, then drive a DC
compressor motor with PWM to run the compressor at exactly the needed speed to
keep the house at the desired temperature. I'd expect it to save power in a car,
too.
4. Power steering is the first thing that got converted to electric with the
introduction of GM's Ecotec engines. GM claimed something like 1/2 mpg from
getting rid of the engine driven hydraulic pump. Driving in a straight line, the
power requirement for electric power steering is zero, and we spend most of our
time going straight.
Mitch.
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