1991 ACURA NSX torque

Oil Pump

The external tooth gear type oil pump consists of a housing together with the main valve body, a pump drive gear, a

pump driven gear, and a pump shaft. The oil pump is installed on the torque converter housing. The pump's driving force

is transmitted by the torque converter pump (directly connected to the engine) to the pump shaft. The gears are provided

in the housing. The intake and exhaust lines and the torque converter line are provided in the housing.

One way Relief Valve

The one-way relief valve is used at times of high speed or high temperature to send relief oil to the oil cooler so that

cooling of ATF will be effective.

(cont'd)ProCarManuals.com

Description
Hydraulic Control (cont'd)
Servo Body/2nd Accumulator Body The servo body is mounted on the secondary valve body with the servo valve, 1st accumulator piston, 3rd accumulator
piston and 4th accumulator piston built in. The primary function of the servo body is forward and reverse switching and

control.

The 2nd accumulator body is mounted on the torque converter housing with the 1st-hold accumulator, 2nd accumulator
and limited slip differential relief valve built in.
1ST-HOLD ACCUMULATOR PISTON
2ND ACCUMULATOR PISTON LIMITED SLIP DIFFERENTIAL

RELIEF VALVE

2ND ACCUMULATOR BODY

SERVO VALVE
1ST ACCUMULATOR PISTON
ATF STRAINER

Limited Slip Differential Relief Valve

When the resistance of oil flow inside the limited slip differential becomes large, the limited slip differential relief valve is
opened, and oil is sent to the ATF cooler and cooled. 4TH ACCUMULATOR

PISTON

3RD ACCUMULATOR

PISTON

SERVO BODYProCarManuals.com

As the engine turns, the oil pump also starts to operate. Automatic transmission fluid (ATF) is drawn from (99) and

discharged into (1). Then, ATF pressure is controled by the regulator valve and becomes line pressure (1). The torque

converter inlet pressure (92) enters (94) of torque converter through the orifice and discharges into (90).

The torque converter check valve prevents the torque converter pressure from rising.

Under this condition, the hydraulic pressure is not applied to the clutches.

(cont'd)
positionProCarManuals.com

1st speed

The flow of fluid through the torque converter circuit is the same as in position.

The line pressure (1) becomes the line pressure (4) and it becomes the 1st clutch pressure (10).

The 1st clutch pressure is applied to the 1st clutch and 1st accumulator, consequently the vehicle will move as the

engine power is transmitted.

The line pressure (1) becomes the modulator pressure (6) by the modulator valve and travels to each shift valve.

The 1-2 shift valve is moved to the right side because the shift control solenoid valve A is turned OFF and B is ON by

the
TCM.

The line pressure (1) also flows to the throttle valve.

NOTE: When used,
"left"
or
"right"
indicates direction
on the
flowchart.

(cont'd)
PositionProCarManuals.com

The flow of fluid through the torque converter circuit is the same as in the position. The fluid (1) from the oil pump

flows through the manual valve and becomes the line pressure (3). It then flows through the 1-2 shift valve to the servo

valve (3), causing the shift fork shaft to be moved in to the reverse position.

Under this condition, the shift control solenoid valve A is turned ON and the valve B is turned OFF as in 3rd speed. As a

result, the 1 -2 shift valve is also moved to the left side. The fluid (3') will flow through the servo valve and manual valve

to the 4th clutch; power is transmitted through the 4th clutch.

Reverse Inhibitor Control

When the position is selected while the vehicle is moving forward at a speed over 6 mph (10 km/h), the TCM out-

puts 1st signal (A: OFF, B: ON), the 1-2 shift valve is moved to the right side. The line pressure (3) is intercepted by

the 1 -2 shift valve, consequently the power is not transmitted as the 4th clutch and servo valve are not operated.

NOTE:
When used,
"left"
or
"right"
indicates direction
on the
flowchart.

(cont'd)
PositionProCarManuals.com

Description

Hydraulic Flow (cont'd)

Position

The flow of fluid through the torque converter circuit is the same as in position.

The line pressure (1) becomes the line pressure (3) as it passes through the manual valve. The line pressure (3) flows

through the 1 -2 shift valve to the servo valve and the servo control valve, causing the shift fork to be moved to the

reverse position as in the position.

However, the hydraulic pressure is not supplied to the clutches. The power is not transmitted.

NOTE:
When used,
"left"
or
"right"
indicates direction
on the
flowchart.ProCarManuals.com

Lock-up System
In position and position in 2nd, 3rd and 4th, pressurized fluid is drained from the back of the torque converter
through an oil passage, causing the lock-up piston to be held against the torque converter cover. As this takes place, themainshaft rotates at the same speed as the engine crankshaft. Together with hydraulic control, the TCM optimizes the
timing of the lock-up system. Under certain conditions, the lock-up operation is applied during deceleration, in 3rd and 4th speed.
The lock-up shift valve controls the range of lock-up according to lock-up control solenoid valves A and B, and throttle
valve B. When lock-up control solenoid valves A and B activate, modulator pressure changes. Lock-up control solenoidvalves A and B are mounted on the torque converter housing, and are controlled by the TCM.
(cont'd)ProCarManuals.com

Description

Lock-up System (cont'd)

No Lock-up

Pressurized fluid regulated by the modulator works on both ends of the lock-up shift valve and on the left side of the lock-

up control valve. Under this condition, the pressure on both ends of the lock-up shift valve are equal, and the shift valve is

moved to the right side by the tension of the valve spring alone. The fluid from the oil pump will flow through the left side

of the lock-up clutch to the torque converter; i.e., the lock up clutch is in OFF condition.

NOTE: When used,
"left"
or
"right"
indicates direction
on the
flowchart.

THROTTLE B PRESSUREProCarManuals.com