Redundant / Hot Spare Fuel Pump?

[EricW]

Hi folks,

I'm getting ready to wire my car completely from scratch, and this time around, I'm adding in a second redundant fuel pump. Per existing rules of my racing sanctioning body, I cannot have two fuel pumps operating at the same time. One must be for backup reasons only.

Three questions come up:

1. Wiring a second pump is super easy with a PDU. One pump to one output, another to a second and PWM them. Easy.

2. How to configure a hot spare setup in the map is the challenge. They would be dual pumps, single rail, but only one operable at a time. I don't think this is an option as I read the note: 

Dual Pumps

This setting is used to set whether or not there is more than one DI Fuel Pump to control and if that second DI Fuel Pump has a completely separate fuel rail to the first with its own pressure sensor.

·OFF - Only one DI Fuel Pump is to be controlled.

·Shared Rail Pressure - Two DI Fuel Pumps are to be controlled but they share the same fuel pressure signal and so are both controlled the same amount using the same PID Loop.

·Separate Fuel Rails - Two DI Fuel Pumps are to be controlled but they each have their own own fuel rail with separate fuel pressure sensors and so each require their own PID Loop and can be driven differently to each other to try and maintain the same pressure in the two separate rails. Note: When using this mode there is some further setup required in the Injector Setup folder to allocate injectors to the two different fuel rails using the Injector Bank Allocation Table so they can be compensated using the pressure from their respective fuel rails. This also means that there are extra Fuel Runtime values when using this mode to show the difference in PW and DC between each bank of injectors.

 

Dual Pump control assumes both pumps are physically identical.

3. Given I want to make them hot spare, I want to (ideally) be able to switch to the backup pump automatically when fuel pressure drops on the rail (think along the lines of a clogged pump filter). A secondary option would be to have a manual switch that allows me to flip over (whether a real DI or CAN input, TBD).

 

Any thoughts from folks? Am what I'm asking about crazy? Should I simply work around the doc and, more or less, just say it's a single pump, and have the map toggle one output or another based exclusively on fuel pressure or the manual switch? 

[Vaughan]

That help manual stuff you are quoting is from the G4X/G5 help manual For High pressure Direct injection pumps. I would assume in your particular case you are wanting to do two low pressure fuel pumps for Port injection.

If you are wanting to talk to a PDU over CAN then depending on the PDU you could just have the ECU send regular single pump control and then have the PDU do the swap over, what PDU are you using? Are you wanting to regularly swap which pump you are using or just always one and then the other only if the first fails? are you allowed any crossover time if you are changing between pumps occasionally?

[EricW]

Thanks for the reply.

Single fuel rail, both pumps sitting on one hangar with one share port to the outlet. Using simple little pumps (don't need crazy large, limited fuel flow benefits due to engine restrictor.

I'm planning on leveraging a PDU, likely an ECUMaster unit. Not wanting to swap regularly, just have a backup. I see two possible ways of triggering the swap:

a) Sexiest: Fuel pressure sensor drops too low

b) Button press (from CAN panel)

I was planning on having the PDU PWM the active fuel pump directly and ditch the fuel pump speed controller for simplicity sake. 

So the question is whether the Link ECU has the concept of fuel pump switching like this? Or should I more or less fake it out by having BOTH pumps tie to the same output for PWM and only triggering low-side A/B selection through another mechanism? My gut says the later.

[Vaughan]

G4+ is a bit more awkward than G4X as G4X has CAN based PWM outputs.

For G4+ I would say use the fuel pump function and send the fp dc over CAN to the PDU and then use a virtual aux with a gp output that controls which pump is being used so the PDU gets an effort % and a this pump or that pump message over CAN.

In terms of determining a failing fuel pump you'll want to have it latch onto the backup pump on failure of the primary which can be done by feeding a gp output's own state back into itself and you might also want to look into detecting a failing pump by watching how much current it draws through the PDU. If you have a manifold pressure referenced fuel reg then you'll want to look at differential fuel pressure not fuel pressure for your failing pressure.

As a side note do the pumps need to be PWM'd?