Trigger to control a big ass fuel pump

Discussion in 'Technical' started by MagicMike, Mar 31, 2016.

  1. Anti

    Anti 14.7 x 14.7 = 44.1

    I don't understand why the FPR can't do it. If it's working as it should and you're draining the surge, fit a larger in tank?
     
  2. MagicMike

    MagicMike Moderator Staff Member

    I have been reading up more on how the speed control works. The description in the pump instructions does leave a gap where is states that less than 0.25V = low speed and greater than 2.5V = high speed.

    I have found a post by fuelab saying that:

    Operating conditions for the pump are:
    - If the Speed Input is grounded or measures less than 2 Volts constant, then pump operates in reduced speed mode (slow enough to be considered continuous duty).
    - If the Speed Input measures 3-18 Volts constant, then pump operates in full speed mode.
    - If the Speed Input reads a pulsed signal (square wave input at approx 1000Hz), then the pump can operate variably, as a function of the signal?s dwell time.

    So going by this, yes the TPS will work easily for what I want. Have to do some testing to make sure it works as intended, but this does seem the easiest solution.
     
  3. MagicMike

    MagicMike Moderator Staff Member

    FPR can do it, but the instructions state that the return that has the FPR on it goes direct to a vented tank (main tank) and not a surge tank. This is where the trouble is because all bypassed fuel (nearly all of it at low load/idle/cruise) is not returned to the surge tank.

    Whichever speed control solution I end up with, the current plumbing has to change so fuel that is bypassed is ruturned to the surge tank.
     
  4. Anti

    Anti 14.7 x 14.7 = 44.1

    In reality will the FPR know the difference?

    You have a system with an FPR designed to run a pump. The surge tank drains because it isn't supplied enough fuel. Why modify that working system to cover up the in tank's flaw?

    I think I must be missing something sorry.
     
  5. MagicMike

    MagicMike Moderator Staff Member

    AFAIK it has to do with where the reg pulls its pressure readings from. Obviously on the rail side for rail pressure, but there is also a sensor on the return side that it uses to compare. When it sees that the return pressure is high it slows pump down, when return pressure is low it speeds pump up.

    If the return is not free flowing (plumbed back into a pressurised surge tank), I assume that the return sensor will show a high reading and the reg will tell the pump to slow down.
     
  6. AndyMac

    AndyMac Better than you

    I like simple solutions.

     
  7. Anti

    Anti 14.7 x 14.7 = 44.1

    I still don't see why you can't plumb the system as intended and fit a stronger in tank.
     
  8. Chrispy

    Chrispy Pretentious Upstart

    Less of the strength and more the size of the return line from the surge to the main tank.
     
  9. rob260

    rob260 Administrator Staff Member

    Mike is the walbro getting constant 12v?
     
  10. MagicMike

    MagicMike Moderator Staff Member

    Yeah. At first we thought it might be a bit slow, but it pumped near 2L in ~15secs into a coke bottle. Still, we ran new wiring and relay etc to be sure.

    Something I have not yet done is run new wiring through the bulkhead from the plug, but that isn't an issue at such low duty.
     
  11. tassuperkart

    tassuperkart Its a lie I tell you!

    At what stage would a surge tank be "sealed" and NOT be vented to the main tank to begin with? How would it de-aerate for starters?

    If the surge tank is setup correctly, the intank lift pump only needs to flow (at no pressure) what the engine will consume at WOT plus a margin of *blah*.

    A big, even giant lift pump fitted to a surge tank thats vented back to the main tank will simply recirculate the surge tank fuel faster, removing heated fuel from the high pressure circuit so no overheating is going to take place anyway.

    I dont understand what the problem here is TBH as far as surge tank plumbing.

    If your desperate to 2 speed the pressure pump then use an additional TPS set to switch somewhere or a pressure switch in the turbo boost pipes.
    That way, your pump runs hard actually when it NEEDS to run hard. not when you tell it to via a TPS switch.

    Variable speed is just fine "IF" you wish to add further reliability issues into a system that simply does NOT need to be complicated as this setup appears.

    E
     
  12. MagicMike

    MagicMike Moderator Staff Member

    The 044 that this pump replaced was full speed all the time and worked well, but the manufacturer does not recommend running these pumps at perma full speed. Otherwise I would.

    My plan of attack at this point to to change the rail return back to the surge tank first of all. Then give the regulator speed control a try in that config. If that works, great, if that does not work well then some other trigger for slow/fast will be required.

    More reading has found a few instances where the regulator does not ramp up the pump fast enough where a motor goes into boost very fast. This is overcome by having the reg feedback at cruise conditions and then break the trigger at some other condition (say 4psi hobbs for example).

    Hopefully I do not run into these issues.
     
  13. tassuperkart

    tassuperkart Its a lie I tell you!

    I should have been a bit clearer Mike.
    When i mentioned variable speed, i was more looking at the added complexity and introduced unreliability buy setting up programmeable PWM pump controllers rather than a simple Hi/Lo switch setup.

    I reckon you have mis-interpreted the destructions with regards to the return. If it say " a vented tank", then that tank could be 3 litres or 75 litres!!!!!!!

    Your return line back to main tank would be 1/2" at least so to present no restriction from the lift pump AND engine pump returns.

    The pressure switch in the manifold is definitely the way to go as opposed to a throttle switch arrangement so the 2 speed becomes a demand only thing.

    It would be nice to configure your switch/relay setup so that the pump, in event of a switch failure (they do-ask me) the system defaults to full speed rather than part speed.

    Id rather see the fool-pump running in a manner not recommended by the manufacturer than your engine running in a manner not recommenced by the manufacturer in event of a switch circuit failure!!!!

    Just me is all!
    E
     
  14. MagicMike

    MagicMike Moderator Staff Member

    Thanks mate, appreciate the feedback :)
     
  15. WazTTed

    WazTTed Grease Monkey

    hobs switch that activates at 5psi boost kicking in your second pump will more then do the trick !! just make sure the surge tank feed line have check valves in them and you will never have any issues !
     
  16. Z32 TT

    Z32 TT Active Member

  17. BLACK BEAST

    BLACK BEAST SLICKTOP TT R-SPEC

    Hey Mike

    Had this setup and scrapped it .. not reliable !

    I ran walbro to 4 litre surge ,fuelab 42401 pump to rail ,52902 reg (-8an )

    walbro to the surge and return to main tank (6an ).

    42401 pump to rail back to surge (8an)

    The 42401 pump was run off the electronic reg ...it worked BUT wasn't speeding the pump quick enough as my motor would rev too quick to redline.
    FUELAB had no answers for me and wanted more data at my expense so they could better the product :confused:

    So using Haltech (from memory)we ran the pump at low speed then full speed at 4000rpm
    the pump ran hot at under half tank or hot day and it shut off .

    I had no problems with running low on surge tank though.

    I run the same set up now but with 2 044's running flat out to rail .

    no problems with at all .

    I had my car at the track for 3 days sitting on 520rwkw revving to 8000rpm.. didn't miss a beat .


    My advice lose that pump and go with walbro's or bosch .



    .
     
  18. mtopxsecret6

    mtopxsecret6 Member

    Chris Rogers(Audio Express). Give him a call. he will get it sorted for you, He is renown all over the world for making electrics work the way you want it too. Tell him I said HI!! haha.
     
  19. MagicMike

    MagicMike Moderator Staff Member

    Yeah I know Chris, but I like Ztoy :)
     

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