pulse width

[Gwoody]

I came across a thread on another forum that got me to questioning myself on how I understood the pulse width tables actually functioned. Is the numbers in the table D0502 the actual time in microseconds that the ecm opens the injector for? That is how I've always understood it but this other thread led me to believe that these numbers were merely a reference point for some type of calculation the ecm does.

[2007 5.9]

I came across a thread on another forum that got me to questioning myself on how I understood the pulse width tables actually functioned. Is the numbers in the table D0502 the actual time in microseconds that the ecm opens the injector for? That is how I've always understood it but this other thread led me to believe that these numbers were merely a reference point for some type of calculation the ecm does.

It is a MAX pulse in each cell the ECM uses..it does not use each value as just that. You set a value in the cells to set a MAX pulse per cell pulse.

[Gwoody]

So, is the actual pulse width determined by some sort of calculation within the ecm and merely raising the MAX values in the table gives a higher MAX target?

[JoshH]

The ECM looks at the actual fuel rail pressure and the commanded fuel quantity. It then uses those values to look up the correct cell in the main injection pulse width table to determine the proper pulse width to fire the injector.

[Gwoody]

So if the commanded fuel rate is 100 mm3 and the rail pressure is 11000 the ecm will see the coresponding cell in the pulse width table and uses this number for the amount of time the injector sprays? This is how I understood it to work but Les's post above states it a little differently.

[2007 5.9]

In a sense we are both correct..if you build a MAP in the logging sw, and run a log, the MAP will populate with values in the corresponding x/y axis BUT the values will be a variant of the commanded value. Table values are a MAX, not a absolute.

[Gwoody]

Is the reason they are a variant due to the fact the tables on the x/y axis have limited number of columns and rows so most of the time the actual readings are always somewhere in between these specific values and so the coresponding pulse width will also be that way?

[2007 5.9]

Is the reason they are a variant due to the fact the tables on the x/y axis have limited number of columns and rows so most of the time the actual readings are always somewhere in between these specific values and so the coresponding pulse width will also be that way?

That is how I understand/approach it.

[Gwoody]

Thanks for helping a newbie trying to understand all this.