What the table does
The Fuel Composition Correction table under ignition corrections adds or removes ignition advance, in degrees, based on fuel composition. It only works when a flex fuel composition sensor is connected and set up, and it's disabled by default.
What values to enter
Enter the timing change you'd want when running the highest ethanol content you'll ever put in the tank. If the strongest blend you use is E85, tune the table for E85. Don't enter the value for whatever happens to be in the tank today.
The reason is how it's blended. The ignition Fuel Composition Scalar table sets what percentage of this correction to apply, based on the sensor's ethanol reading. Set up the usual way, the scalar applies little or none of the correction on straight gasoline and all of it at your maximum blend, with blends in between getting a proportional share.
| Table | Its job |
|---|---|
| Fuel Composition Correction | How much timing to add or remove on your strongest blend |
| Fuel Composition Scalar | How much of that correction to use at the current ethanol reading |
Tune the gasoline timing map first, then add ethanol timing on the dyno using knock monitoring, in small steps. Confirm partial blends too, not only the two ends of the range.
More in our flex fuel tuning guide and the other ignition corrections.
