The fuel map is a 3D, interpolated table that uses RPM and fuel load to lookup the desired VE value. The fuel load axis is determined by whether you are using Speed Density (MAP kPa) or Alpha-N (TPS) for your fuel load (See [Engine_Constants](/en/configuration/Engine_Constants))
The values in this table represent a percentage of the `Required Fuel` amount that will be injected when the engine is at a given speed/load point.
- **Multiply VE value by MAP ratio:** Enabling this option 'flattens' the fuel table by multiplying the value in the current speed/load point by the MAP value divided by either the Baro value (in kPa) or a fixed 100%. Using the `Baro` option adjusts fueling based on barometric reading, but for better results it's recommended to use the [Barometric Correction](/en/configuration/Barometric_Correction) curve instead.
- You can tune with or without this option enabled, but it is generally recommended to be turned on as it will allow for simpler and more predictable tuning results.
- **Multiply by ratio of AFR to Target AFR:** This option is normally set to `No` for most setups. It allows basic closed loop feedback by adjusting the base fuel amount according to how far away from the target AFR the engine is currently running (in %). If the AFR/O2 Sensor type is set to `Disabled` then this setting will have no impact on the fuel calculation.
- **Multiply by ratio of stoich AFR to target AFR ('Incorporate AFR')**: By enabling this setting AFR target is incorporated to pulsewidth calculation. This makes VE table a better representation of actual VE, without AFR targets greatly affecting numbers. After VE table has been tuned, one can adjust an area richer or leaner just from AFR target table, basically without need to touch VE table.
Speeduino also has the ability to use a secondary fuel table which allows for blended and switched mode fueling. There are 2 blended modes and 2 switched modes available.
Blended fuel modes work in conjunction with the primary fuel table to come up with a single, combined VE. Switched fuel modes are where either the primary or secondary fuel table is used, but not both at the same time. Which table is being used at any given time can be configured based on either an external input (Eg dash switch) or set via certain conditions.
This is a blended fuel mode (ie it uses both the primary and secondary fuel tables together) that allows for different load and RPM axis to be combined. Commonly this is used for having primary and secondary fuel tables with different load sources (**Eg:** Primary map using TPS and secondary map using manifold pressure).
This is a blended fuel mode that is very similar to the above `Multipled %` mode. The only difference between the two is that instead of multiplying the values from the primary and secondary tables, the 2 are added together.
This is a less commonly used mode, but is an alternative in the same setups that you would use `Multiplied %`
Dpending on the desired outcome, this can be used to expand the resolution of the main fuel table, automatically handle alternate fuels or as an alternative ITB mode (Particularly if running boosted ITBs).
Input based switch mode let's you change the fuel table that is in use via an external input to the ECU. The options required are:
* The (Arduino) pin that the input is connected to
* The polarity of this input (IE Is the secondary fuel table used with the signal is high or low). For a standard ground switching input, this should be `LOW`
* Whether to use the internal pullup on this input. For a standard ground switching input, this should be `Yes`
