SFI SYSTEM

To match the longer pulsation cycle, the ECM activates the VSV so that vacuum acts on the diaphragm chamber of the actuator. This closes the control valve. As a result, the effective length of the intake manifold is lengthened and the intake efficiency in the medium speed range is improved due to the dynamic effect of the intake air, thereby increasing the power output.

Under any condition except when the engine is running at medium speed under high load, the ECM causes the actuator to open the control valve. When the control valve is open, the effective length of the intake manifold is lengthened is shortened and peak intake efficiency is shifted to the low-to-high engine speed range, thus providing greater output at low-to-high engine speeds.