Does it matter how the fuel injectors are connected to the INJx wires?

In standard SymTech Labs MS1 or MS2 MegaSquirt ECU's, the fuel injectors are fired using a batch fuel injection scheme. This means the injectors are not fired in any particular order, just the same number of times per unit of time. It does not matter which fuel injectors are connected to which bank of fuel injector drivers using batch injection. Many users opt to group the injectors according to the corresponding cylinder's piston position. For instance, in a four cylinder engine, if cylinders one and four are at TDC while cylinders two and three are at BDC, grouping the injectors for cylinders one and four and grouping the injectors for cylinders two and three is a popular choice.

If your MegaSquirt ECU contains a cam sync module and an MS2 processor running MS2/extra 3.0.x or later, or an MS3 processor and MS3X expansion board, you may opt to use semi-sequential fuel injection. Similarly, if your MegaSquirt ECU meets the above criteria, plus a PH Driver or additional fuel injector drivers, you may opt to use fully sequential fuel injection. In these cases it's important to connect each fuel injector to the appropriate injector driver.

For semi-sequential fuel injection, the INJ1 injector driver should be connected to the first cylinder's fuel injector (according to the ignition firing order) and the other injector in the pair. The INJ2 injector driver should be connected to the other pair of fuel injectors. For instance, in a four cylinder engine, if cylinders one and four are at TDC while two and three are are BDC and the firing order is 1-3-4-2, cylinders one and four should be connected to INJ1 while cylinders two and three should be connected to INJ2.

For sequential fuel injection, each fuel injector will have its own driver. Connect the drivers, labeled one through four, to the injectors according to the ignition firing order. For example, a four cylinder engine with a 1-3-4-2 firing order should have injector driver INJ1 connected to the fuel injector for cylinder one, INJ2 connected to the fuel injector for cylinder three, and so forth.

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