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- Toyota fanboy lemmings
April 3, 2011, 11:42 pm
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On 4/6/2011 1:59 AM, Ray O wrote:
Re: Toyota fanboy lemmings
It's a gasoline powered car. Nothing really special at all. And, in
terms of economy, nothing that couldn't be done with a like powered
(gasoline) Corolla. But that wouldn't be as trendy and mysterious thus
high margin which is really what the Prius is all about. Fact is, every
power conversion - gasoline to electricity, electricity to motion is
always accomplished at a loss. Neither of these two losses are present
to a significant degree in 'regular' gasoline powered cars so why not
start there instead of generating more wasted heat. Just another
example of the kooky thinking that passes for science nowadays.
- Daniel who wants to know
April 7, 2011, 11:50 pm
Re: Toyota fanboy lemmings
Kooky? Not special? Hmm... Let's see...
The Prius is a PSD based series-parallel design, usually referred to as a
full hybrid. Most (roughly 2/3rds IIRC) of the engine torque goes directly
to the wheels, the rest does go from MG1-inverter-MG2 thus the speed
difference between the 2 motor/generators sets the effective gear ratio. A
regular cone-belt CVT has a high pressure hydraulic pump to push the
cones/sheaves together and tension the belt. It has no torque converter and
no normal clutch, it does have a dampener between the engine and trans that
has a safety slip clutch sort of like the one on PTO driven farm equipment
that only would slip is something on one side or the other suddenly locked
up solid, this would keep MG1 from overspeeding and blowing apart if the
engine were to seize at freeway speeds.
The engine (1NZ-FXE) has an offset crank so the rods push closer to straight
down during the power strokes, this reduces the side load on the piston
skirts which reduces friction AKA wear and losses.
The engine has a 13:1 physical compression/expansion ratio but the effective
CR is lower and variable due to the intake valve timing, which is controlled
by the VVTi, hence it is closer to the Atkinson/miller cycle than the Otto
The engine also turns much slower on the highway. A regular car has it
clipping along at 3000RPM or higher @ 60 MPH to avoid downshifts, the Prius
with its CVT-like PSD can cruise at less than 1500RPM because when you get
to a hill it smoothly speeds up to meet demand.
And of course as a result even though the Echo and Yaris use essentially the
same engine as the 97-09 Prius, just in conventional Otto cycle trim (lower
CR, 1NZ-FE), and are smaller and lighter (subcompact VS midsize) they still
get less MPG both city and highway.
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