Gastec FP50 Series, Installation Instructions Manual

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3. The "TPS/RPM SET" potentiometer is adjusted differently according to the model being
installed. Carefully place a small screwdriver through the hole (in the rear of the box) to engage
the potentiometer on the circuit board. The initial setup positions are;
FP50-DS-SS
Open Loop at Idle - Adjust the TPS/RPM SET potentiometer slowly until the green ACCEL
TPS SET light on the front of the FP50 blinks rapidly. This will allow richer mixtures at idle (by
holding the stepper valve open). Open loop is the preferred option on vehicles that are
known to backfire on hard acceleration from idle and/or vehicles that “stutter” when
accelerating hard from idle.
Emissions testing has found that running Open Loop operation at
idle generally makes insignificant changes to tailpipe emissions. The TPS voltage at idle
(standard model) must be between 0.2 volts and 1.6 volts. If it is outside of this range you may
not be able to adjust for open loop at idle.
Closed Loop at Idle - Adjust the TPS/RPM SET potentiometer against its minimum stop so
that the green ACCEL TPS SET light on the front of the FP50 remains off. This gives the
maximum economy and minimum exhaust emissions by allowing the stepper valve to operate
around the Lambda point all of the time. Be aware that the majority of the gas required at
idle is
supplied by the needle idle jet . The CV30/CE30 stepper valve only has a significant effect on
the atmospheric diaphragm gas valve. For this reason, stoichiometric control will/may only be
achieved just above engine idle
. Please note that Open Loop operation is the preferred
option as fewer problems are encountered under hard acceleration from idle.
FP50-DC
Adjust the TPS/RPM SET potentiometer slowly until the green ACCEL TPS SET light on the
front of the FP50 blinks rapidly. Continue to turn the potentiometer in the direction of the arrow
another 5 degrees (ie a little bit further).
This sets the TPS setting at which the vehicle will
change over to gas on Deceleration. If it is set too low, the vehicle may stall on Deceleration .
If it is set too high, the engine will need to be revved excessively before (during the
Deceleration phase) the engine will change over from petrol to gas.
FP50-AC
Adjust the TPS/RPM SET potentiometer slowly until the green ACCEL TPS SET light on the
front of the FP50 blinks rapidly. Continue to turn the potentiometer in the direction of the arrow
another 5 degrees (ie a little bit further).
This sets the TPS setting at which the vehicle will
change over to gas on Acceleration. If it is set too low, the vehicle may stall during
Acceleration or it may back-fire during Acceleration . If it is set too high, the engine will need to
be revved excessively before (during the Acceleration phase) the engine will change over from
petrol to gas.
4. The "PETROL OVERLAP" potentiometer is adjusted differently according to the model being
installed. Carefully place a small screwdriver through the hole (in the rear of the box) to engage
the potentiometer on the circuit board. The initial setup positions are;
FP50-DS-SS
Adjust the PETROL OVERLAP potentiometer to midway between the minimum and maximum
stops. This potentiometer adjusts the time
both fuels are allowed to enter the engine during the
cranking (starting) phase.
FP50-DC
Adjust the PETROL OVERLAP potentiometer to one third of its travel from the minimum