Dynalco AF-900PC Air/Fuel Ratio Controller - Manual (Page 43)

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Once in AUTO mode, the controller waits for both pre-catalyst control loops to
stabilize and the pre-catalyst O
2
setpoints to be within a small error before
introducing post-catalyst compensation. At that point the controller will be in its
final mode, AUTO/POST which is automatic with post-catalyst compensation.
12.2 MANUAL Mode
In MANUAL mode, the controller operates entirely in accordance with manually
entered parameter numbers, via DynaHost by the user. MANUAL mode may be
entered and exited only from DynaHost.
In MANUAL mode, the PWM output is determined strictly by the Manual Percent
(%) parameter(s). No automatic control takes place.
Note: It is recommended this mode only be used for troubleshooting by an
experienced user.
13. Control Software
The AF-900PC control software consists of two independent, identical left and right
bank pre-catalyst PI control loops. In addition, a separate post-catalyst offset
control section adjusts both the pre-catalyst loop setpoints in order to compensate
for actual catalytic converter behavior.
During initial system setup, the post-catalyst offset compensation is turned OFF
and the two pre-catalyst setpoints are adjusted until a separate emissions analyzer
shows that exhaust emissions are in compliance. At that point the post-catalyst O
2
sensor voltage is noted and used as the post- catalyst O
2
setpoint. This way the
behavior of the catalytic converter is "captured" in the post-catalyst O
2
setpoint.
Then the post-catalyst offset compensation is turned ON.
During normal operation, both the pre-catalyst loops will react faster to engine
changes and the slower post -catalyst offset loop will adjust the two pre-catalyst
loops based on factors which affect just the catalytic converter performance such
as fuel BTU content, temperature, load, etc...