ACURA NSX 1997 Service Repair Manual

Hydraulic Control (cont'd)
Description

Main Valve Body

The main valve body is located on the torque converter housing. The main valve body houses the ATF pump gears, the

torque converter check valve, the manual valve, the 1-2, 2-3, 3-4 shift valves, the relief valve and the one-way relief

valve.

The primary functions of the main valve body are to switch on and off, and to control the hydraulic pressure going to the

hydraulic control system.ProCarManuals.com

ATF Pump

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

pump driven gear, and a pump shaft. The ATF 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 intake and

exhaust lines, and the torque converter line are incorporated in the housing.

One-way Relief Valve

The one-way relief valve is used during high speed or high temperature to send fluid to the ATF cooler for ATF cooling.ProCarManuals.com

Secondary Valve Body

The secondary valve body is also mounted on the main valve body with the 3-2 kick-down valve, the CPC valve, the 2nd

orifice control valve, the 3rd orifice control valve, the modulator valve, the 4th exhaust valve, the 2nd exhaust valve, the

servo control valve and the 4-3 kick-down valve built in.

Primarily, it regulates shift valve operation timing and clutch pressure for shock reduction during shifting.
Hydraulic Control (cont'd)
DescriptionProCarManuals.com

Modulator Valve

The modulator valve uses line pressure from the regulator (to shift control solenoid valves A/B) and the lock-up control

solenoid valves A/B, to maintain accurate shift and lock-up characteristics.

2nd Orifice Control Valve

For smooth shifting between the 2nd and 3rd gear, the open pressure on the 2nd gear side is relieved through a fixed ori-

fice. The valve also moves to equalize pressure differences between the 2nd and 3rd gear.

2nd Exhaust Valve

The 2nd exhaust valve releases 2nd clutch pressure quickly when shifting from the range where hydraulic pressure is

applied to the 2nd clutch in the position.ProCarManuals.com

Hydraulic Control (cont'd)
Description

Servo Body

The servo body is mounted on the secondary valve body with the servo valve, the 1st accumulator piston, the 3rd accu-

mulator piston, and the 4th accumulator piston built in to it. The primary functions of the servo body are to switch the

direction foward and reverse, and to control hydraulic pressure reduction for shifting shock.

2nd Accumulator Body

The 2nd accumulator body is mounted on the torque converter housing with the 1st-hold accumulator, the 2nd accumula-

tor and the limited slip differential relief valve built in to it.

Limited Slip Differential Relief Valve

When the resistance of fluid flow inside the limited slip differential is high, the limited slip differential relief valve is

opened, and fluid flows to the ATF cooler.ProCarManuals.com

Lock-up Valve Body

The lock-up valve body is mounted on the regulator valve body with the lock-up shift valve and the lock-up timing B valve

built in.

The capacity of the lock-up clutch is controlled by the lock-up shift valve and the lock-up timing B valve.ProCarManuals.com

Hydraulic Flow
Description

General Chart of Hydraulic Pressure

Distribution of Hydraulic PressureProCarManuals.com

position

As the engine turns, the ATF pump also starts to operate. The ATF is drawn from (99) and discharged into (1). Then, ATF

flowing from the ATF pump becomes the line pressure (1). The line pressure (1) is regulated by the regulator valve. 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.ProCarManuals.com

Position

Line pressure (1) becomes line pressure (4), (18), and (25) as it passes through the manual valve. Also, line pressure (1)

goes to the modulator valve through the filter and becomes modulator pressure (6). Modulator pressure (6) is supplied to

the 1-2 shift valve and 2-3 shift valve.

The 1-2 shift and 2-3 shift valves are moved to the left side because the shift control solenoid valve A is turned ON and B

is OFF by the
TCM.

The line pressure (18) is supplied to the 3-4 shift valve, and moves the valve to the left side. Line pressure (4) becomes 1st

clutch pressure (10), and the 1st clutch is engaged.

Line pressure (4) becomes 1st-hold clutch pressure (16) via the 1-2 shift valve, 2-3 shift valve, 3-4 shift valve, and manual

valve, and the 1st-hold clutch is engaged.

NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.
Hydraulic Flow (cont'd)
DescriptionProCarManuals.com

Position

Line pressure (1) becomes the line pressure (4), (25) as it passes through the manual valve.

Line pressure (1) goes to the modulator valve and becomes the modulator pressure (6). The modulator pressure (6) is sup-

plied to the 1-2 shift valve and 3-4 shift valve. The 1-2 shift and 3-4 shift valves are moved to the left side, and the 2-3 shift

valve is moved to the right side, because the shift control solenoid valve A and B are turned OFF by the TCM.

Line pressure (4) goes through the 2nd clutch pressure (20) to the 2nd clutch, then the 2nd clutch is engaged.

Line pressure (4) passing through the orifice becomes the 1st clutch pressure (10) and flows to the 1st clutch. However no

power is transmitted by means of the one-way clutch.

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