2012 Lexus LFA lexus LFA 2012 Technical Information / LEXUS 2012 LFA: INSIDE THE LFA

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When the driver depresses the accelerator pedal, a signal is sent to the ECU where
it is interpreted and used to control the throttle valve angle. This is all performed
electronically without a conventional cable linkage.
The throttle valves are opened and closed by a pair of electric motors, one for each
bank of cylinders. There are a total of 10 individual throttle valves, one for each
cylinder. This configuration minimizes the amount of air between each combustion
chamber and its corresponding independent throttle valve, promoting instantaneous
throttle action for outstanding engine response.
Furthermore, this drive-by-wire technology is able to tailor specific throttle valve
angle strategies to each available driving mode. Depending on which driving mode
is selected, depressing the accelerator pedal the same amount will result in a different
throttle valve angle. This variable control results in engine characteristics better suited
to the driver’s intentions and driving conditions.
■
■Accelerator pedal mechanism
A f l o o r- m o u n t e d a c c e l e r a t o r p e d a l
allows the fulcrum to be moved closer to
the floor and the driver's heel. Depressing
the pedal actuates a rod, which moves
through a sensor. The pedal has a 1.48 in.
(37.7 mm) stroke and the sensor is able
to precisely detect movement down to
0.03 in. (0.8 mm) in order to provide a
more direct feel.
Pedal stroke
Fulcrum
Accelerator pedal (Position sensor judgment)
Pedal
released Pedal
fully
depressed 0 1.48 (37.7)
Pedal stroke [in. (mm)]
Accelerating

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Accelerating
■
■Driving mode-linked variable throttle response
The ratio between how far the accelerator pedal is depressed and the amount that the
throttle valves open is varied to suit the individual driving modes chosen by the driver
using the driving mode selector switch.
In AUTO mode, the maximum throttle valve angle is lowered in order to better
facilitate conservative engine speeds. This control logic was designed to promote
more efficient driving in urban situations and on long distance trips. In SPORT,
NORMAL or WET mode, the maximum throttle valve angle is unrestricted.
SPORT
Engine speed (rpm)
Accelerator pedal angle (%)
Throttle valve angle (° )
WET NORMAL
90
70
50 30 10100 80
604020
01,000 3,000
5,000 7,0009,000

Regarding launch control:
Designed to make the most of the LFA’s abilities, launch control has been
adopted to automatically hold the engine speed at 4,000 rpm when starting off.
Prior to enjoying launch control,
make absolutely certain to read the appropriate
section in the Owner’s Manual.

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Shifting
With regards to the drivetrain, the steering wheel-mounted paddle shift switches
command the automated dry single-plate clutch and rear-mounted ASG (Automated
Sequential Gearbox) transaxle. This fully automated configuration allows the driver to
upshift (+) or downshift (-) while keeping both hands on the steering wheel.
When the driver initiates a gear change using the paddle shift switches, the ASG
computer automatically controls and coordinates clutch engagement, engine speed,
torque transfer and gear select and shift operations.
The engine-mounted dr y single-plate clutch and rear-mounted transaxle are
connected via torque tube to provide the direct feel of a manual gearbox.
The ECU manages gear changes to provide intuitive response to the driver ’s
a c c e l e r a t i o n d e m a n d s . D o i n g s o a l l o w s g e a r c h a n g e s t o b e c a r r i e d o u t
instantaneously, providing a nearly uninterrupted flow of power. The engine speed
is computer controlled on upshifts and downshifts in order to ensure smooth clutch
engagement.
Naturally, shifting can be accomplished manually via the paddle shift switches.
However, shifting can also be performed automatically in AUTO mode. Switching to a
different driving mode using the driving mode selector switch or operating the paddle
shift switches will resume manual operation.
When in a manually shifted driving mode, the shift speeds may be tailored to the
driver’s preferences. Using the shift speed selector, the shift speed can be adjusted in
7 stages to a minimum shift time of approximately 0.15 seconds.

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Shifting
■
■Dry single-plate clutch
A dry single-plate clutch has been adopted to enable a direct engagement feel. The
clutch in the LFA is a hydraulically
actuated unit controlled by the ECU in order to
ensure quick and precise operation.
A pump within the hydraulic power unit generates the hydraulic pressure needed
to operate the clutch. This pump is powered by an electric motor to ensure a stable
supply of hydraulic pressure. In some cases, one can hear the sound of this electric
motor operating prior to the engine starting. This operation provides the hydraulic
pressure needed to disengage the clutch prior to starting the engine.
Because the LFA employs a dry single-plate clutch, it will not exhibit the slow speed
creep associated with a conventional automatic transmission. The driver must normally
depress the accelerator pedal to accelerate, even in ultra-slow speed situations such
as a traffic jam.
Diaphragm spring
Clutch disc The clutch disc is a compact size [9.45
in. (240 mm) diameter] and features
friction material designed specifically
to comply with the engine’s high-output
characteristics. The clutch cover is
c o n s t r u c t e d f r o m a l u m i n u m f o r a
precisely balanced, low-inertia design
that contributes to outstanding engine
response.

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■
■Torque tube
Employing a torque tube to unite the front-mounted engine with the rear-mounted
transaxle creates an outstanding level of powertrain rigidity.
This aspect is essential in order to extract the most performance out of a vehicle. A
rigid powertrain reduces parasitic losses that occur from unwanted engine movement
and input from the wheels, allowing a greater amount of power to be sent to the road
and a more direct response.
Torque is transferred by means of an input shaft housed within the torque tube. This
fast-spinning shaft is mounted using rubber insulators with integrated bearings to
ensure quietness.
Torque tube
Rubber dampers with integrated bearings
Input shaft
Front counter gear Input shaft
A front counter gear is employed,
allowing the engine to be placed
closer to the ground. The engine
crankshaf t axis is lower to the
ground than the input shaft axis.
Crankshaft axis
Front counter gear