911 Turbo F6-3299cc 3.3L SOHC Turbo (1992)
Frequency Valve: Description and Operation
Frequency Valve
CONSTRUCTION
Design and electrical layout is identical to L-Jetronic fuel injector. On fuel inlet side, valve is connected to lower chambers of fuel distributor and is
fitted with a connection leading to fuel return line. Control unit feeds frequency valve square pulses of constant frequency (70 Hz.), but of variable
pulse width. Pulse width is referred to as pulse-duty factor. Since pulse width is subject to constant changes in control mode, this also indicates
system is operative.
Pulse-Duty Factor
OPERATION
If a pulse is present at frequency valve, valve needle opens to allow flow to return line. Pressure in lower chamber drops until frequency valve is
closed again. Since frequency is relatively high, a slightly pulsating medium pressure level is obtained.
