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Steve Bull

Idle control

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Got another question, im using Aux 4 as a PWM to control my fuel pumps. I have a Solid State Relay SSR, to do the high current switching and its set at 1800 hz. This allows control of the pumps to lower the pressure at low demand. At present tick over @35% PWM, gives 30 psi of fuel and maintains a steady 4.5 V

Its yet to be set up fully but what would you recommend to to use as the "Y" axis on the PW table. At the moment its TPs % but i thought it might better to  either MAP or % of the fuel table while keeping the "X" axis as RPM.

I also need to control the Electric PAS pump, I do intend to use another SSR but could the ECU be used on the low side to control it again PWM.

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I would not be adjusting FP speed so much that effects fuel pressure, you really want to aim to keep differential fuel pressure constant under all conditions for the fuel equation to work properly.

For your PWM table I would just do 2D, with inj duty cycle as the axis.  In most typical setups required fuel pump flow is directly proportional to inj DC, there is no need for any other variable to be considered.

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the only reason for dropping the FP that low   on tick over is that the fuel pressure regulator, through manifold depression, does the same.

The pumps can flow 660 lt of fuel per hour which is far too much unless at max boost and revs. The fuel was getting quite warm and pumps drawing too much current when they didn't need to .

 

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Sure, you still want to use PWM, but dont throttle it back to the point were it effects fuel pressure, you want enough excess fuel there so the FPR can do its job and control the pressure with a little headroom left for safety.  When I say "pressure", I mean differential pressure which should be near the same no matter what boost or vacuum is applied to the reg diaphragm.

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