D21 Hardbody 2WD L4-2389cc 2.4L SOHC MFI (KA24E) (1990)
Swirl Control Valve Actuator (SCV): Description and Operation
Swirl Control Valve System
*** UPDATED BY TSB #AM90004 DATED JUNE 1990
CIRCUIT OPERATION
The swirl control valve (SCV), located in the intake manifold passage, partially closes off the intake passage of each cylinder at idle, restricting air
flow. This causes the velocity of the intake mixture to increase, promoting the vaporization of the mixture. This increase in velocity makes the fuel
mixture burn faster, increasing fuel economy and engine stability.
During all other operating conditions the SCV opens allowing the intake flow to encounter less resistance, improving power and acceleration. The
ECU supplies the ground circuit to the SCV solenoid, cutting the vacuum source to the SCV. This allows the SCV passage to open, thereby
allowing non-restrictive air flow.
Fig. 5 Solenoid Valve
SWIRL CONTROL VALVE SOLENOID
The swirl control valve (SCV) solenoid allows vacuum to be applied to the SCV. The ECU completes the ground circuit allowing battery voltage
to operate the solenoid.
Swirl Control Valve Operation
Refer to the chart for SCV operation.
*** The operating conditions of the SCV system were incorrect in the original OE service manual, the above chart shows the correct conditions.