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MegaSquirt This/Next Ignition Mode

Only for use with the MS1 Extra code (MS1 - 68H908 based microprocessors)

By Philip Ringwood (daxtojeiro), James Murrey (jsmcortina) and Ken Calver (muythaibxr)

Please Note:

All of these instructions / diagrams are to be used at your own risk, like most things there is more than one way to do the same thing, what we have tried to do is to offer a method that we have tested or that others have tested for us. No warranty expressed or implied.

Use at your own risk.

The timing to ignite the spark is more difficult to calculate during cranking due to the engine crank acclerating and lack of a steady state. To improve this situation, the spark can be ignited directly during cranking using a trigger wheel position. This will give accurate advance during the uneven cranking period.

During cranking, in Next Cylinder mode, the physical location of the Trigger Angle directly fires the coil and determines the timing. The time to start the coil charge is calculated and determined from the Trigger Angle.


In This Cylinder mode the Trigger Angle can not be used for timing spark directly. As shown in waveform 2, the timing for spark is calculated just as it is during normal running and will therefore be a bit less stable than that of the Next Cylinder mode.

In the special case of waveform 3 the angle between Trigger Angle (falling edge) and Trigger Return (rising edge) is 40 to 80 . When that condition is met, the Trigger Return can be set in TunerStudio to fire the spark The partial settings below show a setting for This Cylinder mode with Trigger Return for cranking timing. When using Trigger Return for Cranking Timing, the Cranking advance Angle must be set to the Trigger Return angle for use by MegaSquirt to set the start of charging the coil.


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