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Calibrating the Cranking and After-Start Fuel Tables |
Cranking Fuel Table
Displays a 2D graph of
injector pulsewidth during cranking based on engine coolant temperature.
At normal operating temperature, this graph is typically set to deliver
40-50% more fuel than is used at an idle. A
simple way to determine a good starting figure is to observe the base pulsewidth
sensor (BPW mS) in the main dashboard display while the engine is fully warmed
up and idling. (You can see the
main dashboard by pressing the F9 key while connected to the ECU.) At the current engine coolant temperature, set the pulsewidth
in the cranking fuel table to 50% more than the pulsewidth observed at an idle.
The colder the engine is, the more cranking fuel it will require for easy
starting. If your engine seems to crank for a long time before it
fires, try increasing the pulsewidth; if the engine produces black smoke or
seems to “load up” when it fires, try reducing the pulsewidth.
Displays a 2D graph of fuel enrichment applied after the engine is started based
on engine coolant temperature. This
enrichment will be applied after the ECU enters “run” mode and it receives
the number of crank pulses specified in the AFTER START REVS VS. CTS graph.
This fuel enrichment will decay out at the rate specified in the AFTER
START DECAY VS. CTS graph. After
start enrichment is helpful for providing additional fuel right after initial
startup to help a cold motor stay running, and it helps prevent a
heat-soaked motor from surging on startup as well.
The presence of after start enrichment will also prevent the ECU from entering closed loop mode. If your ECU will not go into closed loop mode even though all of the closed loop parameters have been met, you should check to see if any after start enrichment fuel is still being applied. Refer to the above diagram. If the sensor called Aft Corr. (%) is at any value other than 0%, it will prevent closed loop operation! If you are having trouble getting your ECU to go into closed loop because after start fuel is being applied for too long, reduce the after start decay vs. CTS settings described below.
After Start Revs vs. CTS
Displays a 2D graph of the number of crank pulses that must be received by the
ECU while in run mode before after start fuel enrichment is applied, based on
coolant temperature. This feature
allows time for excess cranking fuel to be burned before applying after start
enrichment. The higher you set these values, the longer it would
take for after start fueling to begin once the engine is started.
After Start Decay vs. CTS
Displays a 2D graph of the rate at which the after start enrichment will decay
out based on engine temperature. The
decay rate is shown as the number of crank pulses that must be received by the
ECU to reduce the after start enrichment by 0.8%.