Master Fuel (ms) - Master Fuel Trim

[rayhall]

The Master fuel setting is an overall fuel trim. When you change injectors or fuel pressure the master can be adjusted so the tune is back to very close to how it was. Included with the master correction is Master Trim in percentage. This is needed as the Master has a resolution of 1.0. The percentage trim is used to set values with the resolution of 0.1

1. Yes you can use the same formula.

2. Base maps for plugin ECU are for the stock injectors.

3. Below is information from the software online help.

Ray.

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Master Fuel:

The value of Master is the injector pulse width (in milliseconds) that results if the active cell of the of the Fuel Table is set to a value of 100 and the manifold absolute pressure is 100kPa. This does not include any other enrichments or corrections.

Increasing the Master value increases the injector pulse width and hence the amount of fuel injected into the engine. However, changing Master DOES NOT change any value in the Fuel Table or any other fuel adjustments. It is therefore possible to achieve the same tune with a smaller Master and larger Fuel Table numbers as when using a larger Master and smaller Fuel Table numbers.

Note: It is recommended to use a Master value which results in the rows in the middle of the Fuel Table having cell number values around 50 with the desired air/fuel ratios.

Master Trim:

Example:-

Master Pulse Width = 9ms,

Master Trim Percentage = 4%

To calculate the effective pulse width:

Effective Master = Master + (Master * (Master Trim / 100))

Effective Master = 9 + (9 * (4/100))

Effective Master = 9 + 0.36

Effective Master = 9.36

The effective master is 9.36ms.

[rayhall]

If you double the injector size, then the master will be half the old value. So yes 7 is the value.

Rather then calculating the value I prefer to run the engine at 3000 rpm and 100kpa absolute and adjust the master settings so the air fuel ratio is the same as the smaller injectors. This and the calculation method, only works if the bigger injectors have identical control characteristics.

Ray.