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Thread: TD42 fuel pump mods - diesel tuning in general?

  1. #31
    Gas Turbine enthusiast da9jeff's Avatar
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    my guess is: high pressures = tight clearances = not alot of room for error. So you pay a bit for a bloke that knows his shit.
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  2. #32
    Surf's Up! bigmuz's Avatar
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    Cause you can't log mixtures like with petrol and you have to modify a really complex mechanical system to alter the amount of fuel it delivers for a given rpm and throttle opening and boost.. And if you dyno it and it isn't right you have to pull the whole ting to pieces and modify some tiny ports and slots to make it better..
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  3. #33
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    can log mixtures by EGT probes in each runner of the EX manifold,great way to fine tune

    mechanical injector pumps are pretty easy to understand once you get you head around how they work, but yes lots of fine tolerance expensive bits to fix if bad shit happens
    .

  4. #34
    Tin foil hat man.... Buco_73's Avatar
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    I have been messing with several diesels of late. And loads of fun.
    Try this, setup a regulated electric fuel pump feed to the diesel mechanical pump. Start with 5psi and test. Heaps of guys do this shit in the US and it works. Just don't go nuts on the fuel pressure, start off slow and work your way up. Some nutters run 70psi. I've been wanting to do this on my setup, but at 17psi have plenty of fuel left. My issue is I can't get any more boost eve with waste gate fixed shut, turbo is too big for engine. RB20 turbo on a Navara TD27.

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  5. #35
    Registered User bigshipengine.jpg's Avatar
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    So what do you do Buco, leave the electric "Booster" pump running all the time or have it set to operate at a certain load point or boost pressure etc?
    If its running all the time dosent it mess with the normal fueling when the extra fuel isn't required?
    Trying to get my head around it.
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  6. #36
    Tin foil hat man.... Buco_73's Avatar
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    Good question. With a turbo mechanical diesel pump, I'm sure you can take enough fuel out with the electric running all the time and the boost compensator will do the load (turbo boost) fueling.

    Now you bring up a great point I did not think of with a NA mech pump, would be interesting to have some sort of rising rate reg or variable voltage on the electric pump.

    So you could have the elec pump run on minimal voltage and adjust the mech pump so you are not chugging fuel for no reason, then as positive mainfold pressure could could have full 12V to elec pump with pressure reg or both. Would be interesting to setup and test with low tech methods. Less shit to go wrong.

    Wow, we are going back in time 15 years or so, when turbo fuel enrichment was a black art...lol

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  7. #37
    I need more cylinders! nine2nine's Avatar
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    Mechanical pumps have a return line, so the excess fuel just gets returned to the tank. The electric pump is just to make the pump life easier as it doesn't have to draw fuel, but instead has positive pressure.

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  8. #38
    Tin foil hat man.... Buco_73's Avatar
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    Quote Originally Posted by nine2nine View Post
    Mechanical pumps have a return line, so the excess fuel just gets returned to the tank. The electric pump is just to make the pump life easier as it doesn't have to draw fuel, but instead has positive pressure.
    Not quite a true fuel return. The fuel return in a diesel system is called a "leak off" and "over flow". The fuel that is returned is used to lube the injector moving parts hence the little low pressure return line off each injector and the pump housing. And is a small amount compared to a petrol setup.

    Increase in pressure at mech pump = increase in fuel amount. Volume displaced is the same, pressure is greater hence more fuel. No different to a petrol EFI system. Rising rate reg with boost = more fuel. It is just crude and a global fuel trim.

    You can also get your injectors high flowed. I was going to get mine done, but at the time I was told the TD27 injectors are the same size as the QD32. 2.7L = 3.2L, and my mech pump would supply plenty of fuel even for the QD32 boosted. So did not bother.

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  9. #39
    Surf's Up! bigmuz's Avatar
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    Correct- the bleed is a mechanical orifice so squeezing fuel in may help.

    It may also piss fuel everywhere and create a trainsmash/ debacle.
    Quote Originally Posted by Stix Zadinia
    2x Robbie Williams Tickets, Brisbane, Monday Night 22nd Sept, Row A Platinum
    Quote Originally Posted by Shifty
    Won't be much of a show now that he's dead.
    Quote Originally Posted by agentcrm
    ROBBIE Williams the singer not ROBIN Williams the recently deceased Actor & comedian

  10. #40
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    this intrests me.
    i have just rebuilt my 4jb1t out of an isuzu mu and wondering what mods i can do.
    I have got 3 inch pipe waiting to go on it,
    she was running 16psi before the rebuild just not sure how much boost it would be able to handle, fuel screw was played with a bit but propaly not enough.

  11. #41
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    hobbs switches can be a bitch to set up,

    i`ve got one of these to go on the hilux when
    i bolt the monster pump on when it (eventually) arrives
    http://www.fassride.com/shop/fuel-pu...fuel-pumps.php

    also, with some mechanical pumps, its easy to change the relief spring and valve ( VERY exact sized ball bearing) to fuel it up a bit. not one for amateurs tho
    Last edited by 15UZU; 08-06-11 at 09:51 PM.
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  12. #42
    Registered User ls400x's Avatar
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    I think the lift pumps give best results on pumps with worn internal vane pumps, or, where there are leakes in the line between tank and IP allowing air to be sucked in. The vane pump is a positive displacement pump so the lift pump should not cause a great change.

    for VE style IP pumps have a read of: http://legionlandrover.com/manuales/...20instructions

  13. #43
    Registered User ls400x's Avatar
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    Also, massive changes to the IP inlet pressure due to lift pumps may give changes to pump timing as this is related to thepressure after the vane pump, which is also a function of shaft speed.

    In short, big IP inlet pressures may artificially advance the injection timing.

  14. #44
    Registered User ls400x's Avatar
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    Quote Originally Posted by Buco_73 View Post
    Increase in pressure at mech pump = increase in fuel amount. Volume displaced is the same, pressure is greater hence more fuel. No different to a petrol EFI system. Rising rate reg with boost = more fuel. It is just crude and a global fuel trim.
    I'm not sure that is entirely correct as the fuel is an incompressible liquid and the pump is positive displacement, pressure is developed by the resistance to flow.
    Last edited by ls400x; 09-06-11 at 09:31 PM.

  15. #45
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    Quote Originally Posted by ls400x View Post
    I'm not sure that is entirely correct as the fuel is an incompressible liquid and the pump is positive displacement, pressure is developed by the resistance to flow.
    Beat me to it.

    Isn't diesel not compressible?

  16. #46
    Registered User ls400x's Avatar
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    I couldn't find a copy of the Bosch VE injector pump technical overview .PDF but it's worth a read to.

    Outerlimits forum has some good discussion on td42 IPs involving people who work on IPs for a living. The vw diesel forums also have good information because the older ones used VE pumps.

    Ih8mud forum, also some good applicable theory.

  17. #47
    Registered User ls400x's Avatar
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    Quote Originally Posted by TehEkHo View Post
    Beat me to it.

    Isn't diesel not compressible?
    Incompressible, yes. The result of more delivery pressure cannot be compared with a petrol engine. At some nominal load the IP will deliver x volume of diesel to the injector, the resistance to flow of the injector will determine the line pressure. In a petrol engine for x injector open time, the volume passed will be determined by the line pressure that is set by the regulator.

    As an analogy think manual grease gun, it's going to deliver say 1g of grease per pump regardless of it's inlet pressure or what it's attached to, assuming no air is mixed in and no leakage past the piston.
    Last edited by ls400x; 10-06-11 at 09:10 AM.

  18. #48
    Tin foil hat man.... Buco_73's Avatar
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    Both petrol and diesel are considered incompressible fluids. Engine oil is, so is brake fluid. But they all operate a various working pressures that vary greatly. Even at zero pressure (rel), they are at atmo pressure.
    So a diesel fuel injector opens at a predetermined pressure, if we increase the total working pressure of the system, basically what we have changed is the injector open time. Basically if at pressure X the injector opens, we need to supply a fuel pressure of X+1 to deliver enough fuel for combustion and injector will close once the pressure drops to just bellow pressure X. If we increase the pressure to X+2 the injector will be open for longer and deliver more fuel. Given that volume flow is a function of pressure, more fuel is being injected.
    Diesel mechanical pumps control volume and duration not timing. Timing is static. The counter weights (governor) determine the fuel volume at rpm (mapping). We are talking about a very basic system here, no high tec gear. Unthrotled operation where only additional fuel allows the engine to rev up. Only the new electronic systems with common rail setups vary the injection timing dynamically.
    Correct me if I'm wrong.
    Last edited by Buco_73; 16-06-11 at 09:26 PM.

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  19. #49
    ass bandit Supercrown's Avatar
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    Yep - all liquids can be considered incompressible for practical purposes.
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  20. #50
    Registered User ls400x's Avatar
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    Quote Originally Posted by Buco_73 View Post
    Both petrol and diesel are considered incompressible fluids. Engine oil is, so is brake fluid. But they all operate a various working pressures that vary greatly. Even at zero pressure (rel), they are at atmo pressure.
    So a diesel fuel injector opens at a predetermined pressure, if we increase the total working pressure of the system, basically what we have changed is the injector open time. Basically if at pressure X the injector opens, we need to supply a fuel pressure of X+1 to deliver enough fuel for combustion and injector will close once the pressure drops to just bellow pressure X. If we increase the pressure to X+2 the injector will be open for longer and deliver more fuel. Given that volume flow is a function of pressure, more fuel is being injected.
    Diesel mechanical pumps control volume and duration not timing. Timing is static. The counter weights (governor) determine the fuel volume at rpm (mapping). We are talking about a very basic system here, no high tec gear. Unthrotled operation where only additional fuel allows the engine to rev up. Only the new electronic systems with common rail setups vary the injection timing dynamically.
    Correct me if I'm wrong.
    You could be right but I'm not sold on your theory. The way I see it is that the shot delivered to combustion chamber will be near enough to the displacement of the plunger.

    I wish I had a copy of the VE operational literature at hand. From memory combustion event time is fixed, therefore injection has to advance as engine speed increases to get peak cylinder pressure occurring at the correct crank angle. This is achieved by cam plate or follower (probably follower, I cant remember, it sounds more practical) controlled the body pressure of the IP determined by the vane pump and regulating valve. I would say that the pump controls injection volume and timing and the duration is only determined by the engine speed and cam plate.

    I'm not sure how the timing is controlled further on the td42ti pumps.
    Last edited by ls400x; 18-06-11 at 07:17 PM.

  21. #51
    Surf's Up! bigmuz's Avatar
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    Buco is wrong. Supplementing the input pressure will only increase the output a small amount.

    The pump outputs a fixed chamber of fuel per injection event and increasing the pressure of the fule into the pump won't increase the amount of fuel in the chamber as fuel is incompressible. It would remove any air bubbles or pumping losses into the chamber but these are almost zero unless something is broken.

    You also need to read up on diesel injectors Buco- they are simply a valve with a preset pressure that they crack off the seat at to then inject fuel through a very small orifice in a very fine mist. They aren't involved at all in determining injection quantity or timing.
    Quote Originally Posted by Stix Zadinia
    2x Robbie Williams Tickets, Brisbane, Monday Night 22nd Sept, Row A Platinum
    Quote Originally Posted by Shifty
    Won't be much of a show now that he's dead.
    Quote Originally Posted by agentcrm
    ROBBIE Williams the singer not ROBIN Williams the recently deceased Actor & comedian

  22. #52
    Surf's Up! bigmuz's Avatar
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    To increase the amount of fuel you need to increase the stroke of the pump or the size of the chamber. Once you set the pump to it's maximum stroke you are out of easy solutions.

    Big truck diesels use buttons in the pump to decide how much of the stroke you have available based on hp requirements and how hard you want to run the things. In a low duty thing like a ferry or local truck you would only use half the possible stroke to stretch maintenance and reduce fuel usage. In an interstate truck you would use more of the pump to try and keep your average speeds/ driver happiness up.

    So there are engines rated at 350 hp and 500 hp that are identical other than the pump settings.
    Quote Originally Posted by Stix Zadinia
    2x Robbie Williams Tickets, Brisbane, Monday Night 22nd Sept, Row A Platinum
    Quote Originally Posted by Shifty
    Won't be much of a show now that he's dead.
    Quote Originally Posted by agentcrm
    ROBBIE Williams the singer not ROBIN Williams the recently deceased Actor & comedian

  23. #53
    Surf's Up! bigmuz's Avatar
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    In fact the paxman diesel in the state rail xpt I used to work on was rated at 2500hp but you could have that engine in a patrol boat rated to 5500hp with only a pump mod and a few hundred extra revs.
    Quote Originally Posted by Stix Zadinia
    2x Robbie Williams Tickets, Brisbane, Monday Night 22nd Sept, Row A Platinum
    Quote Originally Posted by Shifty
    Won't be much of a show now that he's dead.
    Quote Originally Posted by agentcrm
    ROBBIE Williams the singer not ROBIN Williams the recently deceased Actor & comedian

  24. #54
    Tin foil hat man.... Buco_73's Avatar
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    I see, the vane pump pressure controls the timing and the governor controls the fuel mapping. Asked a few diesel guys and was told that a TD27 has a fixed injection timing. According to them the counter weight governor maps the fuel curve and that there is no timing control. Interesting. So I see that so called experts don't seem to know as much as they assume they do.
    So can the timing be remapped?

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  25. #55
    Registered User ls400x's Avatar
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    This should answer some questions.

    http://etc.gnarlodious.com/Vanagon/B...h_VE_Pumps.pdf

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