Frequency Valve: Description and Operation

Fig. 3 Pulse relationship chart:

The modulating valve comprises an injection valve of a slightly modified design from the EBI system. The valve operates (opens and closes) at a constant frequency of 70 Hz as soon as the engine is running.
The pulse relation Fig. 3, is the relationship between the time the valve is open to closed. Through variation of this relationship it is possible to regulate the pressure in the chambers of the pressure regulating valves. During the warm-up period before the operating temperature of the catalytic converter has been reached, or in the event of a system malfunction the pulse relationship is 60/40. The valve will be open for 60% of the time and closed for 40%. This is the relationship for idling or partial load. A longer opening interval of 80% will create a much richer air/fuel mixture.
Enrichment of the mixture under load is achieved by the use of a switch on the throttle valve. This fixes the interval at approximately 45%, a richer mixture than the interval of 30% which would otherwise be the case under full load.