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# Injector Pulsewidth to Crank Angle degrees Calculation

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Discussion and questions related to the course EFI Tuning Fundamentals

Hi, I want to convert the injector pulsewidth for example (4 milliseconds) at 3000rpm to equivalent crank angle in degrees. From Hondata SManager, the injection angle is set at BTDC of Compression stroke and the injection angle value is the MIDDLE of pulsewidth. On Speeduino side, the injection angle value is the END of pulsewidth set at ATDC of Intake stroke. I want to copy it to my Speeduino.

My calculation is:

3000rpm * (1min/60sec) * (360deg/1rev) = 18,000 degrees/sec or 18 degrees/millisecond = 72 crank degrees of 4 milliseconds pulsewidth

From SManager, Low Load at Hot Temperature is 480 BTDC of Compression stroke = 120BTDC of Intake stroke = 600ATDC of Intake stroke. Since it is in the middle of pulsewidth, it is only 2ms instead of 4ms. 2ms = 36 crank degrees. 36 + 600+ = 636 ATDC of Intake stroke.

Now from Speeduino side, when Sequential injection is selected, the 355 value = 715 ATDC of Intake stroke. The equivalent of 636 ATDC = 360-636 = 276. So from my understanding, at 3000rpm, the close angle equivalent from SManager at 480BTDC of Compression stroke at 4ms injector pulsewidth is 276. Is my calculation correct? Thanks

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