DL1 PWM Output/PWM fuel controller equation

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Joined: Fri Apr 29, 2011 6:05 am

DL1 PWM Output/PWM fuel controller equation

Postby Bikey » Tue Mar 08, 2016 12:40 am

Hello - I have a car with two fuel tanks (a left and a right) that will be running ethanol and gas in varying amounts and also various states of de-tune (depending on the power to weight class entered for a given event). I have one fuel pump in each tank that pumps to a surge tank, and then connected to the surge tank is a main pump that pushes fuel to the injectors.
I would like to setup the PWM outputs on a DL1 to control an OEM fuel pump controller module so that the in-tank pumps output an appropriate amount of fuel given the fuel content and state of de-tune. The OEM fuel pump controller varies the output of the fuel pump that it is connected to based on the duty cycle of the (100Hz) PWM signal that controls it (which is sent by the DL-1).
For setting up an equation, I think it makes sense to base the calculations for the PWM duty cycle off of the Injector Duty cycle percentage as that will take into account various tune levels and the ethanol content (note that the main pump is also a PWM pump and is controlled by the ECU, though that pump has a built-in controller that has different duty cycle and PWM frequency requirements).

Here is my initial equation - with the goals of (1) in higher g situations, forcing the pump on the outside of the turn to pump at full output, (2), satisfying the fuel pump controller's need for at least a 20% duty cycle to work and (3) correlating the in-tank pump's output with the injector duty cycle. Note that a 70% duty cycle from both in tank pumps will provide more than enough fuel for the main pump, if the main pump is running at full output (i.e., at 70% each, the two pumps provide can output more than the main pump can flow and will easily keep the surge tank filled or refill it, if needed)

Verbose equation for left side tank:
PWM duty cycle =
If [Lat G] < -1.1, then 100% PWM output duty cycle, otherwise [If injector duty cycle is less than 21%, then 20% PWM output duty cycle, otherwise [if injector duty cycle is greater than 80%, then 70% PWM output duty cycle, otherwise PWM output duty cycle % = .833*[Injector duty cycle] +3.33]]
Or, to put into the DL1:
If [Lat G] < 1.1, 100, [if [Inj D/C] <21, 20, [if [Inj D/C] is >80, 70], .833*[Inj D/C]+3.33]

Does this look right? Will this pose any issues for the DL1?


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