wheel torque ACURA NSX 1991 Service Repair Manual

Service Precaution s
Handling o f Specia l Nut s an d Bolt s
Becaus e man y section s o n thi s ca r ar e constructe d wit h
aluminu m alloys , us e onl y th e specia l "Dacro " typ e
nut s an d bolt s recommende d b y Acura .
NOTE:
Dacro finis h ca n b e identifie d b y gra y plating .
Som e Dacr o finis h bolt s hav e a gree n coatin g o n
th e threa d sectio n of the bol t fo r easie r applica -
tion . Thi s typ e of bol t i s calle d a "Torquer " bolt .
Us e o f othe r type s of nut s an d bolt s ma y caus e
electrolysi s an d corrosion , whic h in tur n coul d
caus e th e bol t t o loosen .
Gray platin g
Green coatin g
on th e thread s
Gray plating : "Dacro " typ e
Gra y platin g + Gree n coatin g o n th e threads :
"Torquer " typ e
1. Whe n replacin g nut s an d bolts , us e onl y th e sam e
type.
2. Tighte n th e nut s an d bolt s with a torqu e wrenc h t o
th e specification s provide d i n thi s manual .
3 . Clea n al l threa d ridge s wit h a non-wire-typ e bristl e
brush . Foreig n matte r i n th e thread s ma y caus e th e
bol t t o loosen .
4 . Section s o n thi s ca r requirin g th e us e o f Dacr o nut s
and bolt s wil l b e indicate d b y a ( ) in thi s manual .
Handling o f Tire s
The tire s o n NS X & NSX- T shoul d no t b e rotated . Th e
fron t wheel s ar e 16 " in , diamete r an d th e rea r wheel s
ar e 17 " in , s o the y canno t b e rotate d front-to-rear .
Th e original-equipmen t tire s o n NS X & NSX- T hav e
a unidirectiona l trea d pattern , s o the y canno t b e ro -
tate d side-to-side .
Th e foldin g spar e tir e canno t b e repaire d o r remove d
fro m th e rim .
Engin e Steam-cleanin g
(NSX-T only )
When steam-cleanin g th e engin e compartment , kee p th e
roo f holde r switc h dry . I f th e roo f holde r switc h get s we t
accidentally , dr y i t thoroughl y wit h compresse d air .
Roo f holde r switc h
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Preset Torque

Inspection
On-Car:

1. Lift up right rear wheel,
and place the safety stand.

(Lift and Support Points, see section 1).
2. Block the other three wheels.
3. Measure preset torque clockwise using a torque wrench as shown.

Standard:
60–140 N·m

(6–14 kg-m, 43–101 Ib-ft)

Service Limits: 30 N·m (3 kg-m, 22 Ib-ft)

TORQUE WRENCH
RIGHT REAR WHEEL SAFETY STAND

4. If preset torque is less than the service limit, replace the clutch discs with new ones.
NOTE: Adjust the thrust shim whenever the clutch
discs are replaced (see page 15-22).
Assembly:

1. Place one special tool in a vise. Place the left side of the differential assembly on the special tool, then
preset the differential with 3 – 5 rotations, both
clockwise and counterclockwise.

DIFFERENTIAL
INSPECTION TOOLS

07MAJ– PR90100

2. Measure preset torque clockwise using a torque wrench as shown.

Standard: 60–140 N·m
(6–14 kg-m, 43–101 Ib-ft)

Service Limit: 30 N·m (3 kg-m, 22 Ib-ft)

TORQUE WRENCH
DIFFERENTIAL
INSPECTION TOOLS

07MAJ – PR90100

3. If preset torque is less than the service limit, replace the clutch discs with new ones.
NOTE: Adjust the thrust shim whenever the clutch

discs are replaced (see page 15-22).
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System Description

Major Components

The Electrical Power Steering system is composed of the following major components:

• A steering gearbox that converts rotary operation of the steering wheel into transverse operation via a rack and pinion

mechanism. Steering sensors and an actuating motor are incorporated.

• A control unit that computes the optimum amount of power assistance, taking into account steering torque, steering

speed, and vehicle speed. Self-diagnosis functions are included.

• A power unit that drives the motor according to the signals from the EPS control unit. A current sensor is built in to

give feedback information to the EPS control unit. Two relays shut off the power if a problem in the system occurs.

• The countershaft speed sensor on the automatic transmission or the differential speed sensor on the manual transmis-

sion sends a vehicle speed signal to the EPS control unit. Also the speedometer sends a vehicle speed signal to the EPS

control unit. The two signals are used as a double-check.ProCarManuals.com

System Operation

Manual Steering Operation

Steering wheel input rotates the pinion of the gearbox through a universal joint. Due to the rack and pinion mechanism,

the rotation of pinion is converted into a transverse motion at the rack, which steers the front wheels throught the tie-rods

and knuckles the same as an ordinary rack and pinion system.

Assisting Operation

In addition to the manual steering operation, the steering sensor on the pinion shaft transmits a signal to the EPS control

unit when it receives a steering input. The EPS control unit calculates an adequate motor control with addition of vehicle

speed signals. Based on the signal from the sensors, the EPS control unit drives the motor inside the gearbox. The torque

generated by the motor is transmitted to a ball screw, through gears, and converted into an assisting thrust in the axial

direction of rack. The assisting thrust acts in the steering direction and lessens the steering force required at the steering

wheel.

EPS CONTROL UNIT

RECIRCULATING

BALL SCREW

STEERING WHEEL
RACK

STEERING SENSOR

(Build in the rotation sensor

and torque sensor)

MOTOR

STEERING GEARBOXProCarManuals.com

System Description

Function and Operation

Steering Sensor

The steering sensor consists of a torque sensor, an

interface, and the rotation sensor.

Torque Sensor

The torque sensor converts steering torque input and its

direction to voltage signals, in conjunction with the

interface.

A torsional force caused by steering operation is con-

verted to an axial movement of a slider core. A variable

differential transformer is installed around the slider

core.

Within the transformer are three coils, a primary coil on

the inside, and two secondary coils, one for right turns

and one for left turns.

Alternating current is passed through the primary coil

when the system is energized. The amount of mutual

induction from the primary coil to the secondary coils

changes depending on the position of the slider coil.

The input shaft and the slider are one piece. Rotation of

the shaft moves the slider in a circular direction. The

pinion is turned via the torsion bar. The slider core is

installed on the pinion shaft on grooves, and turns with

the pinion shaft.

When there is little resistance, the input shaft torsion

bar, pinion shaft, and the slider core turn together to the

same angle. The slider core does not move up/down.
TORSION BAR

INPUT

SHAFT

INTERFACE

CIRCUIT

SPIRAL

GROOVE

ROTATION

SENSOR

GUIDE

PIN

TRANSFORMER

PINION GEAR

WING

When there is resistance on the input shaft (hard to steer situation), and the slider pin is turned at an angle by the steering

wheel, the torsion bar is twisted due to the resistance. Accordingly, the pinion shaft turns at a smaller angle. The differ-

ence in the turning angles changes the position of the slider pin in the groove, forcing the slider core upward or down-

ward, depending on the direction of the direction of the turn.

PRIMARY COIL

UPPER SECONDARY COIL

LOWER SECONDARY COIL

SLIDER
SLIDERProCarManuals.com

Rotation Sensor

The rotation sensor is housed inside the steering gearbox near the pinion. It converts the rotation speed and direction of

steering into voltage signals. The rotation of the steering wheel is transmitted to the pinion, which drives the sensor by

accelerating its speed through the three pieces of transmission the gears. Acting as a kind of direct current generator, the

sensor generates direct current voltage proportionately with the rotational speed of the pinion. When the steering direc-

tion is reversed, the voltage is generated in the opposite direction. No power is generated when driving straight ahead

without turning the steering wheel.

Interface Circuit

The interface circuit is housed inside the steering gearbox near the pinion. It rectifies and amplifies the signals from the

torque sensor and the rotation sensor, and transmits the steering signals to the EPS control unit. A phase compensating

circuit is also built in, which changes the output signals in accordance with the drive signals input from the EPS control

unit.

TRANSMISSION GEARS

INTERFACE CIRCUIT

ROTATION SENSORProCarManuals.com

6. Install the new self-locking nuts on the top of the

damper assembly.

7. Tighten the damper mounting nut to the specified

torque.

8. Secure the damper assembly to the frame with the

self-locking nuts.

9. Install the strut brace.

10. Install the rear hatch glass trim.

11. Install the engine cover support rod onto the strut

brace.

12. Install the rear wheels.ProCarManuals.com

Illustrated Index

The accumulator contains high-pressure nitrogen gas; do not puncture, expose to flame or attempt to
disassemble the accumulator or it may explode; severe personal injury may result.

HYDRAULIC SYSTEM
Relieving Accumulator/line pressure, page 19-62 ('91-'92) ('93-'96)

MASTER CYLINDER
Index/Torque, page 19-12

Inspection, page 19-13

ABS CONTROL UNIT Replacement, page 19-70

BRAKE BOOSTER

Tests, page 19-14 Pushrod clearance adjustment, page 19-15

UNDER-HOOD

RELAY BOX B

UNDER-HOOD
FUSE/RELAY BOX

REAR WHEEL SENSOR

Inspection, page 19-71

Replacement, page 19-72
POWER UNIT
Torque/Inspection, page 19-66
ACCUMULATOR/PRESSURE SWITCHIndex/Torque, page 19-67 FRONT WHEEL SENSOR
Inspection, page 19-71
Replacement, page 19-72
MODULATOR/SOLENOID UNIT

Index/Torque, page 19-63 ('91-'92) ('93-'96)
Solenoid Leak Test, page 19-64 ('91-'92) ('93-'96)
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6. Clea n th e calipe r thoroughly ; remov e an y rust , an d
chec k fo r groove s an d cracks .
7. Instal l th e pa d retainers .
11. Pus h i n th e piston s s o tha t th e calipe r wil l fi t ove r
the brak e pads .
12. Se t th e calipe r dow n int o position , the n instal l th e
brak e hos e mountin g bolt s an d th e calipe r moun -
ting bolts . Tighte n th e bolt s to th e specifie d torque .
8. Appl y Molykote ® M7 7 t o bot h side s o f inne r shi m
A an d th e bac k o f th e pads . Wip e exces s greas e of f
th e shims .
9 . Instal l th e brak e pads .
• Whe n reusin g th e pads , alway s reinstal l th e
brak e pad s i n thei r origina l position s t o preven t
los s o f brakin g efficiency .
• Contaminate d brak e disc s o r pad s reduc e stop -
pin g ability . Kee p greas e of f th e brak e disc s o r
pads .
NOTE :
• Instal l th e inne r pa d wit h it s wea r indicato r fac -
ing upward .
• Appl y Molykote ® M7 7 t o th e shim s (se e pag e
19-5 ). Wip e exces s greas e of f th e shims .
10 . Instal l th e brak e pa d shim s correctly . 13
. Depres s th e brak e peda l severa l time s t o mak e sur e
the brake s work , the n test-driv e th e car .
NOTE : Engagemen t of the brak e ma y requir e a
greate r peda l strok e immediatel y afte r th e brak e
pad s hav e bee n replace d a s a set . Severa l applica -
tion s of the brak e peda l wil l restor e th e norma l
peda l stroke .
14. Instal l th e fron t wheel s an d torqu e th e whee l nuts .
NOTE : Clea n th e matin g surfac e o f th e whee l an d
hu b befor e installin g th e wheel .
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11. Install and tighten the two caliper mounting bolts.

12. Insert the cable through the arm, and connect the

cable to the lever with the clevis pin and new lock

pin.

Install the new cable clip securely.

13. Install the caliper shield.

14. Depress the brake pedal several times to make sure

the brakes work, then test-drive the car.

NOTE: Engagement of the brake may require a

greater pedal stroke immediately after the brake

pads have been replaced as a set. Several applica-

tions of the brake pedal will restore the normal

pedal stroke.

1 5. Install the rear wheels and torque the wheel nuts.

NOTE: Clean the mating surfaces of the wheel and

hub before installing the wheel.ProCarManuals.com