Just about the cheapest mod you`ll see... *Update - Now with added boost*

Discussion in 'Diesel' started by StuMc, Oct 16, 2010.

  1. A.N. Other Banned after significant club disruption Dec 5th 2

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    Ok - aspirin to hand [:p] - I now understand why two components are being combined in to one. Instinctively it feels leftfield, almost as if the switch / pot is being made to do something it wasn't designed to do (implicitly there could be combined current 'issues' in the unit by doing it this way, but evidently not).

    The wiper, standalone, I understand. Switch, ok, ignore the unused half. So it's basically like a dimmer light switch in a house?

    The bit I still don't follow... we're bleeding current/volts/amps out of wires to/from the fuel pump, by interfering with the feed, short circuiting it in effect.

    => surely cue a load of heat build up in the pot/switch, as this electrical energy is continually bled off and held elsewhere? Risk of heat?
    => why does the fuel pump inject more fuel, when it's receiving less current to action fuel delivery? Implicitly an engine turned off or ignition only would deliver full fuel... (I know, that's bollox!).

    Electrics... IT... I hate it!
     
  2. m1keh Forum Member

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    The voltage you are bleeding off is a signal voltage not a control voltage. The signal voltage the ecu is seeing once bled off is lower so it believes the fuel pump is not pumping as much as it should be. So this then means the ecu puts more control voltage to the pump controlling valve thus acheiving more fuel being injected.

    This signal voltage is also very low current, thus why you do not get excessive heat build up in the pot/resistor.
     
  3. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    It`s designed to be operated this way!

    By leaving the two components (electrically) seperate, it gives the end-user the option of how he wants to configure it/them. :thumbup:

    And as m1keh says, it`s only a signal voltage. This means it`ll be no more than 5v and mere milli-amps of current. You wouldn`t even feel it if you put your tongue to it! :lol:

    Why does less voltage mean more fuel?;

    Counter-intuative, yes, but actually it`s a product of the mechanical motion of the plunger, so easy to explain/visualise.

    Imagine the plunger as a piston in an engine; it moves up and down displacing/delivering an amount of fuel determined by the volume of the `cylinder` it runs in. This happens hundreds of times a second in direct correlation to engine revs.

    If the stroke is lengthened therefore there is more volume of fuel available for delivery, and vice versa for a shorter stroke.

    The twin-coil position-measuring set-up I explained previously is detecting the piston moving up/down, so this creates a `pulse` signal voltage which is almost a perfect sine-wave;

    [​IMG]

    For a shorter stroke/less fuel delivered the plunger is moving less distance so the frequency/wavelength of the signal is smaller/shorter. The ECU`s fuel map will expect certain frequencies of signal for given loads, temps, etc.

    By `bleeding off` some of this signal we effectively shorten the wavelength, so the ECU lengthens the plunger stroke (more fuel delivered) to bring all the parameters back in line.
     
    Last edited: Nov 20, 2010
  4. A.N. Other Banned after significant club disruption Dec 5th 2

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    More answers, cue more questions...

    5 volt current => where did 7 volts go? Another resistor? Is it creating heat somewhere? Or is it 'ok', same as the pot resistor?

    The pump - how can the stroke alter? Is it a floating plunger working off electromagnets? I always thought it was impossible for a pump actuation to fail, being mechanical? Sounds like it's reliant on electrics [:s]

    Bloody complicated shizzle!
     
  5. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    In post 76 I put a link as to how a transformer works. This is what is happening in the plunger sensing arrangement. The 7 volt `loss` is dissipated as heat, but at the coils of the sensor. It`s within the pump where it`s hot anyway, but the actual heat produced is virtually nothing.

    Think of, say, your laptop charger; it`s dropping 240v down to just 9v (typically) and whilst warm, is certainly not hot enough to cause concern. Much less here, and it`s not being lost within the componentry were adding anyway.

    Saying the plunger stroke is physically altered, was to simplify it for ease of understanding (as was to say it goes `up and down`) but now you`be asked I`ll have to explain it properly... [><] :lol:

    The plunger is connected to the input shaft (via a spring) by a `cam-disc`. That is a flat disc with four cam-profiles riding on a set of rollers, so converts the rotational motion into a linear (horizontal) motion.

    The fuel passes into the plunger chamber via a solenoid (magnet) valve where it it is then pressurised as the plunger moves forward. It travels through the centre of the plunger to one of four ports, set at 90deg to each other and corresponding to each injector/cylinder.

    The ports are covered by a variable `control sleeve`, which controls how much of the port is revealed, thus determining how much fuel is delivered. Obviously, therefore fully opening the port is maximum fuel delivery.

    This metering of fuel in this way is the `effective stroke` of the plunger. It`s the position of the control sleeve that is being measured as explained earlier, and is altered by the ECU. A servo is used to alter it`s position.

    The timing can also be altered by rotating the cam-disc to alter the profiles. This done by a hydraulic cylinder operated by another solenoid.

    See? Dead easy... :lol:
     
  6. A.N. Other Banned after significant club disruption Dec 5th 2

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    Fookin complicated pump! Understand ref transformer (conceptually).

    Did the mod today and... it doesn't work [:s] I had differing resistances on the multimeter - 1 down to .650 roughly, but initially nothing. The pot seemed to create resistance after being connected for a bit, with no current in the wire [:s]

    So onto the road test and nothing. Idle steady, nothing [:s]

    The only thing I did differently was grabbed the wires at the ECU plug, rather than the pump plug, for ease/neatness. Continuity ok from the pot wires to the fuel pump plug, proving it was in circuit.

    And having lowered the fuse box down to feed wires into the scuttle, my driver's side sidelights have gone AWOL, front and rear + rear fog!

    I * hate * electrics, gadgets and IT [:x] I detest them so much I've an image of something punched through the laptop screen at times! My fist!

    Pass the aspirin!
     
  7. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    Probably a bad connection somewhere...

    You won`t be able to measure anything of value with a standard multimeter, when it`s all hooked up.

    To test that the pot and switch are good, you need to check the resistance with it disconnected from the fuel pump wiring.

    You should see zero ohms across the two wires, with the switch in the off position. With it switched to `on` (just past the `click`) it should read around 1500 ohms, then gradually drop to 500 ohms as you sweep all the way to the end. (Take a note of the switch position at around 800 ohms.)

    If all`s well there then re-connect to the fuel pump wiring. Is there definately a clear run in the wiring from the plug to the ECU? If so, then there`s nothing wrong with tapping in nearer the ECU for neatness. Make sure your soldering is good and strong.

    With the engine running at idle; turn the switch on and slowly wind it down until the idle becomes rough. This should correspond more-or-less with the 800 ohm position you`ll have noted earlier. Turn the switch back till the idle just begins to smooth out. This is your `sweet spot`.

    If that works, you`re good to go. :thumbup:

    Actually, just to check; you are winding it down far enough to affect the idle aren`t you?
     
  8. A.N. Other Banned after significant club disruption Dec 5th 2

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    Right, progress update. I think there was some sort of faulty wire, not 100%, but it was cut & resoldered last night.

    I can't quite get the engine to bog down like yours at idle Stu and have been turning it 'all the way to 11' just out of searching for where the sense of humour failure kicks in. I know the max resistance is about the 650 ohms mark, but I may bridge in a wire over the resistor just to see what effect this will have.

    On to a very limited (so far) test drive, the difference is subtle, but I can feel it's zipping through the gears quicker. I induced 'Warp Drive Collapse' once off the lights (limp mode) and used less resistance on the subsequent run & it was ok.

    Will report back after some more mileage and testing (+ m/way) and if it seems worthwhile, get an optimal setting sorted & I'll get it onto the dyno for some back to back data. I've calibrated the adjuster with tippex!
     
  9. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    Yeah, I`d do away with the resistor. Sounds like it`s not allowing you to go quite low enough. No harm in trying at any rate, and I`m yet to have a limp-mode, even with it wound right down as far as I dare, and full-bore launch.

    You`ll definately know about it when the idle `roughens`, since it`ll feel a bit like a petrol engine mis-fire. Note the revs don`t actually drop though, it just runs rough.

    I`ll hopefully get some useful back-to-back figures at Sam`s RR-day in a couple of weeks. :thumbup:
     
  10. aidanb22 Forum Member

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    Any updates on the injectors?
     
  11. A.N. Other Banned after significant club disruption Dec 5th 2

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    I shorted it with a key and managed to get it to stall on the switch, so that's given me an idea.

    I'm continuing to experiment with the settings.

    Why is the aim just off the engine stalling area for the sweet spot?

    Otherwise, is this a linear switch adjustment on the pot, according to how much extra power is sought?
     
  12. m1keh Forum Member

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    Chris, if your hitting limpmode/warpfield collapse when accelerating from lights with it turned up too much then I wouldn't take the resistor out. Probably due to aging fuel pump or similar your car is not giving the noticable change in character at idle.
     
  13. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    You`ve felt how cold it is outside, right??... :lol:

    (Should be doing them this week all being well.)
     
  14. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    That`s because it`s reached the point where it`s simply too rich. Back of a little from there, and your at the max point where it can handle the volume of fuel, aka; the Sweet Spot.

    Linear adjustment?...Yes...no...maybe...

    In theory it should be linear, but since the boost isn`t being increased commensurate with fuel being delivered, you`ll reach a `saturation point`, when the ECU gives up and throws it into limp mode. Upping max boost should give you more adjustment, but then you`ve potentially got too much boost low down.
     
  15. ourkid Forum Member

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    You fairy!

    I had the whole week off work to finish my car,(outside) no coat,no gloves or hat...or socks,slept in the boot.Dedicated to the cause
    [xx(]
     
  16. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    -12 in Manc yesterday... [:s]

    Two years ago I started the 20v in similar weather, and I promised `never again`. Oh well! :lol:
     
  17. m1keh Forum Member

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    Come on fairy boy, we need to see the smoke clouds you can produce with the bigger nozzles.
     
  18. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    :lol:

    This weekend...most probably Sunday.
     
  19. m1keh Forum Member

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    Stu, have you invested in another very cheap mod that you can do. DIY cruise control?
     
  20. StuMc

    StuMc Moderator and Regional Host - Manchester Moderator

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    Tell me more...

    Is it a simple retro-fit?
     

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