lexus LFA 2012 / LEXUS 2012 LFA: INSIDE THE LFA Service Manual

39
Shifting
■
■Rear transaxle
The LFA’s gear change mechanism consists of a parallel two-shaft layout often used
in modern manual transmissions. In the LFA, the transmission and differential are
integrated and placed near the rear axle, thus realizing a rear transaxle configuration.
Gear shift and select commands are sent by the ECU to a hydraulically operated shift

mechanism for fast and precise operation.
To ensure ample strength and the ability to handle the engine’s broad torque curve,
various areas throughout the transaxle have been reinforced and high-capacity three-
point contact bearings have been adopted. Furthermore, each synchronizer ring
employs a high-friction carbon material to realize quicker engagement and faster
shifts. Additionally, the teeth of all speed gears have been micro-polished for precise
engagement and reduced gear whine.
The transaxle employs its own oil pump and oil cooling system to ensure a constant
supply of oil at a stable temperature even under demanding endurance conditions.
3rd 6th 5th 2nd 1st
Support bearings
Regarding synchronizers, 1st through 4th gears employ triple-cone units while 5th and 6th
gears are double-cone. A TORSEN
® LSD (Limited Slip Differential) with a specific amount
of preload dialed in has been adopted to ensure excellent traction and handling stability.
TORSEN
® LSD is a registered trademark of JTEKT. 4th

40
■
■Paddle shift switches
I t i s u n d e rs t o o d t h a t d r i ve rs t e n d t o
anticipate downshifts more than upshifts.
To mechanically reflect this phenomenon,
the downshift paddle shift switch (-) has
a comparatively higher force pull than
the upshift paddle switch (+) to foster
a g re a t e r s e n s e o f exc i t e m e n t w h e n
stepping down a gear.

Automatic processes that occur during gear changes
Engine speed control
When the driver commands an upshift, the ECU will automatically lower the engine
speed to facilitate the gear change without requiring the driver to release the
accelerator pedal.
Blipping control
When the driver commands a downshift, the ECU will automatically raise the
engine speed in order match the speed of the transaxle, ensuring smoother clutch
engagement.
Automatic downshift control
The ECU will au tomatically downshif t when the vehicle slows to below a
predetermined speed. This will occur even in a manually shifted driving mode.
Downshift (-) Upshift (+)

41
Shifting
■
■Driving mode-specific shift characteristics
The driving mode selector switch allows the driver to choose the automatically shifted

AUTO mode or a manually shifted SPORT, NORMAL or WET mode and their
corresponding default shift speed level. The driver may perform gear changes using the
paddle shift switches while driving in a manually shifted driving mode. While the shift speed
is adjustable using the shift speed selector, each driving mode has its own default shift
speed setting. Shift speeds are determined by how quickly the following operations are
carried out: Clutch disengagement, gear select, gear shift and clutch engagement.
Selecting a faster shift speed will shorten the time it takes from the moment the paddle shift
switch is pulled until the shift is totally completed. Faster shift speeds allow for enhanced
response and near-seamless power delivery, but will also result in a greater amount of shift
shock due to the speed at which the aforementioned operations are carried out. Selecting
a slower shift speed will allow the clutch and gear shift/select mechanisms to operate at a
more gentle pace, leading to a smoother application of torque and less shift shock.
Driving modeDriving mode default shift speed
AUTO ■■
2/7 (Non-adjustable)
SPORT ■■■■■□□
5/7
NORMAL ■■■□□□□
3/7
WET ■□□□□□□
1/7
Shift characteristicsLevel 1 n Level 7
Shift speed Slow (approx. 1 sec.) n
Fast (approx. 0.15 sec.)
Shift shock Less n
More

Shift speed selector
When in a manually shif ted driving
mode (SPORT, NORMAL or WET),

the shift speed can be adjusted from
l e v e l 1 t o 7 u s i n g t h e s h i f t s p e e d
selector.
Shift speed is also determined by the
accelerator pedal angle. The more the
accelerator pedal is depressed, the
shorter the shift times will be.
S106-04
Fast
Slow
Fully released Fully
depress
Level 1
Level 2 Level 7
Accelerator
pedal angle
Shift speed

44
Steering
The driver’s steering inputs are conveyed by a large-diameter main shaft housed
within an aluminum alloy steering column, then through a joint made as straight as
possible onto the intermediate shaft. From here, inputs are mechanically transferred
to the wheels by an aluminum alloy monoblock steering gearbox. This efficient flow of
steering commands helps ensure a direct steering feel and precise wheel placement.
Joint Column assist type EPS
Aluminum alloy steering column
Intermediate shaft
Joint
Steering gearbox
The LFA’s power steering system features a column-assist type EPS (Electric Power
Steering) system. This computer-controlled system takes into account factors such
as vehicle speed, steering effort and steering rate in order to provide linear steering
feedback. Furthermore, the teeth of the reduction gear, a section of the motor
responsible for sending large amounts of torque to the main shaft, have been coated
with power grease to reduce torque fluctuations and provide smoother steering feel.

45
Steering
■
■Steering wheel
The steering wheel features a flat-bottomed design that has 1.10 in. (28 mm) of the
lower half cut away. This reduces the steering wheel’s inertial moment and locates
the wheel’s rotational center and its center of gravity in almost the same place, almost
completely eliminating any imbalance within the steering wheel itself, reducing the
amount of steering fluctuations imparted by lateral and vertical forces. Ultimately
this provides the driver with a more natural and accurate steering feel. Furthermore,
the use of an aluminum alloy frame and hollow CFRP rim reduces the inertial force
generated by steering inputs.
H o l l o w C F R P
steering wheel rim
Center of rotation
Center of gravity
Turns lock-to-lock: 2.35
Aluminum alloy frame
Steering wheel center

46
■
■Steering rack and gearbox
The steering gearbox consists of a monoblock aluminum alloy rack and pinion unit
mounted to the front suspension member using four rigid mounts. This allows the
driver to feel as if they are solidly connected to the road. An overall steering ratio of
14.3:1 allows the driver to precisely follow their intended line through a corner.
S107-06The joint between the steering shaft and gearbox is set at a narrow angle (approx. 10˚)
for a highly efficient connection that allows even subtle steering inputs to be accurately
conveyed, keeping the LFA directly on the driver’s intended path no matter what the
situation, whether it be a winding road or an extremely fast straightaway. Joint angle: Approx. 10˚

47
Steering
■
■Suspension
The LFA is equipped with a double wishbone front suspension and multi-link rear
suspension.
The front suspension features two independent lower arms that shorten the offset of
the virtual kingpin axis from the wheel centerline along with a slightly negative kingpin
offset in order to ensure ample stability under braking. Furthermore, the low offset
between the kingpin axis and wheel centerline allows for excellent road compliance
and outstanding stability.
Ground contact patch kingpin offset
Wheel centerline
Kingpin offset
Virtual kingpin axis

Regarding suspension adjustments:
The LFA is equipped with adjustable coil spring perches in order to allow for
any fine tuning needed to keep the geometry optimized at all times. Each LFA is
shipped from the factory with the suspension adjusted to the optimal settings.