These parameters control closed loop operation. Closed loop when the ECU uses an oxygen sensor input to alter the air/fuel mixture in order to achieve maximum fuel and catalytic converter efficiency.
Closed Loop Options
Closed loop operation may be one of the following options:
Open loop (closed loop disabled)
This setting disabled closed loop. Disable closed loop while tuning. Otherwise the ECU will adjust the air/fuel ratio resulting in an inconsistent air/fuel ratio.
Closed loop - stock sensor (narrowband)
This is the normal setting with the stock oxygen sensor.
Closed loop - wideband input (voltage target)
This setting uses a wideband lambda voltage input as the oxygen sensor input, with a simple voltage target. See Wideband target voltage and Closed Loop Advanced Parameters.
Closed loop - wideband input (target lambda)
This setting uses a wideband lambda voltage input as the oxygen sensor input, with a dynamic lambda target. The wideband input pin and target lambda are specified in Closed Loop Advanced Parameters.
Narrowband target voltage is the target oxygen sensor voltage when using the stock oxygen sensor. Normally it is around 0.5V.
Wideband target voltage is the target wideband voltage. Normally it is around 2.35V.
Disable the o2 heater if the stock oxygen sensor is physically present.
Closed Loop Conditions
Maximum Map for closed loop determines the maximum engine load for closed loop operation.
Maximum engine speed is the maximum rpm for closed loop operation.
Delay after engine start is the delay after starting the engine before the ECU will start to run in closed loop.
Closed loop max TPS is the throttle position switch point from closed loop to open loop operation. There are two tables - High is the switch from closed to open loop and Low is the switch from open loop back to closed loop. Note that a value of 99% will disable open loop from TPS position.
Long term Fuel Trim Settings
The minimum and maximum long term adjustment sets the limits for the long 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.
Short term Fuel Trim Settings
The minimum and maximum short term adjustment sets the limits for the short term fuel trim in the same way as the long term settings.
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.