I am using an e38 in an LS3 engine swap, no GM FPCM is used. However I would still like to have PWM fuel pump control via the PWM which flows from X1 pin 50.

So far tests via HPTuners allow me to manually enable the output with a percentage via the scanner and this can be seen in a scope with a 128Hz frequency and any duty cycle percentage I choose to try via the scanner. However as they are only tests I do not know the real world range of duty cycles that will likely flow under regular operation at say, idle and WOT (I assume these would be the two extremes).

So my question is does anyone know what the regular, real world range of duty cycles look like on this X1 50 pwm output at both idle and WOT?

One reason I ask is that consider the situation with the PWM controlled thermal fans. Enter any percentage above 91% in the tables (or manually try to select 92% or more for the fan speed in the scanner) and the pwm output for the fan just completely shuts off. Whether this is a feature or a bug who knows, but is the driving reason why you never put greater than 91% in your desired fan speed table.

So in a similar way, does the real world Fuel PWM output show the same behaviour? That is, are there any duty cycle percentages at each end of the range in which no PWM output is delivered? Note that I am not asking this question from the aspect of "how much is enough". I'll get to that part later when it comes to tuning. For now, I'm trying to understand the technical limits the e38 can actually punch out

When there is no FPCM module used, the e38 only offers the table for fuel pressure (I think?) It is not a direct percentage that you can enter for duty cycle. I am sure there must be some basic interpolation the e38 is doing to still dump a PWM demand out of X1 50 at certain duty cycles, but what range of duty cycles that exactly is, I just don't know.

The main reason I'm asking is that I am programming an Arduino to accept the e38 PWM output for the fuel pump and it will do some interpretation of this to then drive an independent fuel pump controller. At this early stage, knowing the real world range of duty cycles that the e38 pumps out at both its very minimums and very maximums, in terms of a duty cycle percentage, will solve my problem.

I'm hoping someone will come back and say something like "4% minimum, 95% maximum. Anywhere outside these bounds and the pwm stream shuts off, aka how the thermo fans do it".

Thanks,
Matt