These parameters control closed loop operation.
Disable closed loop while tuning. Otherwise the ECU will adjust the air/fuel ratio resulting in an inconsistent air/fuel ratio.
Disable the o2 heater if not oxygen sensor is physically present.
Maximum Map for closed loop - this determines the maximum engine load for closed loop.
Target voltage - sets the target o2 sensor voltage for closed loop operation.
Use wideband input for closed loop - allows the use of a wideband lambda input to be used for closed loop operation. The wideband input pin is specified under Wideband Lambda Parameters. The wideband stoichiometric voltage (air/fuel ratio 14.7) should be specified as the wideband target voltage (normally 2.5V).
Closed Loop Settings
The minimum and maximum short term adjustment sets the limits for the short term fuel trim. The values are expressed as a percentage adjustment of fuel eg. -10% means that the short term fuel trim will not remove more than 10% fuel from the table.
Closed Loop Rate of Change
The short term trim rate of change can be altered in order to produce better operation under closed loop, both for a normal oxygen sensor input and when using a wideband lambda input.
There are three settings, each broken down into four rpm bands:
| • | Slow - this defines the normal rate of short term fuel trim change. |
| • | Fast (rich to lean) - sets the faster rate of change when short term fuel trim starts to decrease. |
| • | Fast (lean to rich) - as above, but for when the short term fuel trim starts to increase. |
Normal closed loop operation
Normal closed loop operation gives 1-2 cycles from lean to rich to lean per second. The short term fuel trim swings up to 10%.
Closed loop operation with the fast rate of change increased.
By changing the short term fuel trim rate of change it is possible to reduce the amount of short term fuel trim swing. This gives better fuel economy and a smoother running engine.