EFI University

[giskard]

Injector dead time will differ from the manufacturer spec if the "flyback" voltage your ECU applies to the injectors is different than that during the manufacturer's tests.

Here is a method for measuring dead-time in-car.

Procedure:

Idle car while datalogging, and have a means of changing injector electrical pulse width slowly up and down while logging. Car must have a reasonably stable idle at a fairly fixed RPM, and battery voltage must be constant throughout.

Log MAP, AFR, Battery volts, and Injector electrical pulse width, while idling. Slowly raise and lower injector on time (I did it by changing the injector dead time vs. battery voltage, across 3 cells, straddling the battery voltage that I was seeing). Slowly raise and lower it until the RPM starts to drop significantly or the car starts to misfire. I could go from 11:1 to 16.3:1 or so and back. Do this several times, it may take you a few minutes.

Then examine the datalogs. Do an XY plot. Plot MAP divider AFR on the X-axis, then injector on-time on the Y-axis. You can use your log viewer, or MS Excel. Excel has the advantage of having a linear curve fit ("trendline, linear"). The datapoints should form a line. If you project this line to the Y-axis, the intercept is the dead time.

In Excel, do a scatter plot, then add a trendline. Select "linear", and in the options, select "show equation". If your data is clean and has little noise, the Y-intercept will show in the equation. If not, select "Set Intercept", and try different values until the trendline appears to describe the quiet part of the data.

[Flr Power]

giskard,

You forgot to include the Excel file. lol

[giskard]

I wanted to post the plot, but this forum doesn't have provisions for attaching images, or am I wrong?

[El Verdugo]