Megasquirt Support Forum (MSEXTRA)

I could use some confirmation on my injector Dead Time input into Tuner Studio "at 100%".
[Picture 1] I measured my deadtime by running varying duty cycles to create a CC/pulse value and compared that to the PW. The X intercept of that line turned out to be 0.963ms (deadtime) at 12.1 volts for the one shown, the average of the set turned out to be 0.982ms [shown in pic 3].

[Picture 2] I took the voltage correction chart from TS and plotted it to get a linear equation so that I can see the deadtime offset at 12.1v. [Picture 3] I do not have all of the voltage data points, so I wanted to use the same curve but input what I measured as a known deadtime.

I found that there was a 122% offset at 12.1v, so I divided my 0.982 by 1.22 and got 0.808ms. I used this value, 0.800ms, as my "Deadtime at 100%" value.
.....is that right??

Bump, am I missing something? Thanks-


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I got roughly 0.950ms from you data.

ol boy wrote:I got roughly 0.950ms from you data.

0.950ms @ 100%?

May I ask how you calculated that?


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Here is my spreadsheet.

I took data off of two injectors and averaged it. Not the most capable process, but the averaging should help clear up some of the variation.

I did a back of the napkin calculation (literally) and came up with a dead time of 0.936 ms @12.1 volts so I think your 0.963 ms is probably in the correct range for the raw data in your first picture. I didn't do a least squares fit on your data and calculated the slope from 2 data points only so your number could easily be the better one.

I am not an MS3 user, so I don't necessarily follow the logic for the voltage correction. I assume that you are trying to correct the injector offset to the standard reference point of 13.2 volts using what I assume to be a standard correction line in MS3? As an observation, I would not attempt to do a linear extrapolation of the offset from your 12.1 volt values. I went through this characterization exercise for my injectors and discovered that the injector offset change with operating voltage was decidedly non linear. You might want to repeat your flow test at your typical operating voltage (13.8 - 14 volts ?) so that you know that you have an accurate offset at that point and then extrapolate to other voltage that may be less common.

If you have some other data (i.e. the data in picture #3 came from actual flow tests at different injector operating voltage - I was unsure about that part) which indicates that the injector offset versus voltage follow the slope you are using, then I agree that your offset at 100% / 13.2 volts looks correct.