Calibrating the Cranking and After-Start Fuel Tables

9.0 Calibrating the Afterstart and Cranking Fuel Tables

9.1 Overview

These tables basically act as your “choke” function. The Cranking Fuel Table is your main cold-start table and the After-start Enrichment Tables function as the “when, how much, and how long” functions for the “choke”. Your engine will operate in two modes while these tables are in effect. The first is Crank mode, where the Cranking Fuel Table takes effect. The second is Run mode, where the After-start Enrichment Tables take over the “choke” function. See Crank to Run Mode RPM and Engine Revs to Run Mode

9.2 Cranking Fuel Table

This table mainly affects cold start-up. It is displayed as 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.

9.3 After Start vs. CTS

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, acting as somewhat of a “choke” function. This table is displayed as 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.

IMPORTANT NOTE - 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.

9.4 After Start Revs vs. CTS

This table is displayed as 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.

9.5 After Start Decay vs. CTS

This table is displayed as 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%. The higher you set these values, the longer it would take for the after start fuel to decay out once it was applied.