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Hybrids are hot. Politicians and Hollywood stars, futurists
and environmentalists; everyone is talking about how
hybrids are the new "green-machines" capable of saving the
globe from the ills of automotive pollution and reducing our
nation's dependence on foreign oil. Think hybrids are just
on the fringe? Success in selling its Prius Hybrid is given as
one strong reason why Toyota surpassed General Motors in
global sales earlier this year.
Toyota and Lexus Change the Game
Toyota and its luxury Lexus brand provide an interesting
example of how hybrids are changing. The company was an
early adopter of the technology, which in essence involves
putting in two separate powerplants to propel the vehicle.
An electric motor with a limited supply of battery power can
be used to move the vehicle at low speeds and with no pollution.
At higher speeds, an efficient gasoline engine provides
power to the wheels and also charges the battery system.
Braking energy is also captured to charge the battery
pack. Under hard acceleration the electric motor and the
gasoline engine work in tandem, combining their respective
outputs for quicker acceleration. This means a smaller gasoline
engine can give the performance of a bigger engine,
while reducing exhaust emissions and improving fuel economy.
Traditionally, in a vehicle such as the Prius, the bias
was toward lower fuel consumption and emissions, while
maintaining economy-car levels of acceleration and performance.
But then Lexus took a step in a different direction,
using the electric motor more as a means to enhance
performance than as a way to build the ultimate eco-friendly
vehicles many envisioned the hybrid would be. As a result,
Lexus now has hybrid versions of its sedans and sport utility
vehicles that are optimized for performance.
The Flagship
Let's say you're Lexus. Your first effort at a luxury car in
the 1990s outflanked Mercedes-Benz and you've been going
from strength to strength ever since. Your top-of-the-line car,
the LS 460 is going into its fourth generation. It's popular,
defines the luxury segment and makes a ton of money for
Toyota-but some critics, especially the enthusiasts, find it
"uninvolving" to drive. You've staked out your claim in the
mid-priced luxury market but you need a flagship for your
Lexus brand. Something that makes a statement that
Mercedes-Benz or BMW or Audi can't make. That is the
idea behind the 2008 Lexus LS 600hL. According to Bob
Carter, Lexus Group Vice President and General Manager,
"The Lexus LS600hL is the ultimate Lexus statement. It
provides the highest level of performance and technology,
and the truest expression of luxury and efficiency of any
vehicle we have created. The hybrid model transports the LS
to a place where Lexus has never been before, and will
expand our presence among the ever more-discriminating
customer."
First, it's a Hybrid
Although the Lexus LS600hL is brimming with technology
(see sidebar), it is the gasoline-electric hybrid powerplant
unique among its competitors. The gasoline part of the
equation is a new 5.0-liter direct injection double-overhead
camshaft V8, producing 389 horsepower at 6400 rpm and
385 lb-ft of torque at 4000 rpm. The engine features variable
valve timing that electronically controls both intake and
exhaust camshaft timing to optimize engine performance
over a broad engine-speed range. The engine is equipped
with what Lexus calls a Hydrocarbon Adsorber. During cold
starts, catalytic converters aren't very effective at removing
hydrocarbon emissions. The new Lexus system absorbs
those hydrocarbons initially and then sends them back into
the exhaust stream after the engine has warmed so they can
be burned. This and a host of other technologies in the
engine have resulted in its Super Ultra-Low Emissions
Vehicle (SULEV) pollution rating.
By itself, the new 5.0-liter V8 engine is state of the
automotive art, but what comes next moves it to the next
level. The electric motor generator of the hybrid drive system
is actually located with the new all-wheel-drive electronically
controlled continuously variable transmission. The
water-cooled motor generator has an output of up to 22-
horsepower and can turn as high as 10,240 rpm. It also acts
as the starter motor for the engine. When braking, the device
works as a generator and recharges the hybrid's battery system.
A compact Torsen® limited-slip differential is integrated
with the rear output shaft of the transmission to distribute
torque between the front and rear axles. The torque split is
normally 40/60 front to rear but can change up to 30/70 to
improve vehicle stability under acceleration.
The hybrid battery pack is located in the sedan's trunk
and consists of 240 sealed nickel metal hydride (Ni-MH)
high-voltage batteries. The nominal voltage of the system is
288 volts and the batteries are expected to last the lifetime
of the vehicle.
The hybrid system is electronically controlled, but the
driver can choose between three different throttle response
modes: POWER, for improved acceleration and response,
HYBRID, for everyday driving and SNOW, for better control
on slippery surfaces. The continuously variable transmission
has eight speed ranges that correspond to maximum
speeds in each range. A hybrid power meter shows which
direction the energy is flowing during acceleration, constant
speed and braking.
For more on this article and much more grab a copy of Auto Aficionado Magazine on newsstands nationwide!
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