Fuel system upgrades.
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  1. #1
    1000+ Posts jo proffi's Avatar
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    Default Fuel system upgrades.

    What do you guys who have efi'd carby cars do about fuel starvation???
    The 'ignore it' option has now worn very thin.

    My car suffers it rather badly, and i'm considering putting a surge tank in bolted to the floor of the car up back where all the fuel stuff is already, and run by a second pump (outside the car of course).
    This one on ebay looks like a ripper.
    None of that bling anodised crap that looks so 'bmx'.
    http://cgi.ebay.com.au/BTR-VL-commod...8#ht_632wt_907

    I have spare pumps at my disposal so this looks like an elogamnt solution and dirt cheap.

    Does anyone know if there are any rules and regs pertaining to fuel system mods, and any tips or traps.


    Jo

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    Last edited by jo proffi; 10th May 2011 at 12:29 PM.

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    Budding Architect ???? pugrambo's Avatar
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    hsort of cutting your tank open and placing extra baffles in there the best thing is a surge tank

    a mate of mine and my self decided doing this to a scorpion with magna injection on it back in the early 90's and there was nothing we could find then that stated we couldn't do it but it solved the fuel startvation problems he was getting as the car was being driven up and down macquarie pass 5 days a week and it was driving him insane

    all we did as the car didn't have an in tank pump but we did fit the injection pump to it which was needed was to make up sump if you like and went from there
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    Jo,

    205s suffer badly from this, although it varies from car to car for some unknown reason. We built a tall, thin surge tank, with a VL pump inside, and the fittings welded to the lid. It went under the bonnet, between the existing fuel filter and the fuel rail. The return line to the fuel tank was also plumbed into, and out of it, so the surge tank was always full, at the same pressure as the return line. The relay was fed from the Autronics brain, same as the existing fuel pump. Worked a treat. Can't help you with the RTA rules.

    Tim

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    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by tcusack View Post
    Jo,

    205s suffer badly from this, although it varies from car to car for some unknown reason.

    Tim
    Here is a potential reason.

    I never had any issue when both inlet and outlet were the same length, pushed within 10mm of the bottom of the tank.
    Then I got some silly idea that the outlet should vent above the inlet not next to it so I cut the return line shorter and all my troubles started.

    I'm sure this was the difference because it never happened before the cut.

    Jo

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    COL
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    Hi Jo

    There didn't happen to be a reduction in the pipes ID where you cut the pipe off the return line, which would reduce the pressure in the system causing the fuel starvation you say you have
    Regards Col

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  6. #6
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by COL View Post
    Hi Jo

    There didn't happen to be a reduction in the pipes ID where you cut the pipe off the return line, which would reduce the pressure in the system causing the fuel starvation you say you have

    Nah, the efi pump is more than capaple of 100psi if you want to make it a non feedback system, so the issue with orifice size after the regulator is more a mater of constriction and richness, not enlarging and leaning out.
    It only chokes on corners or acceleration, and can hit red line WOT up hill in third gear without a problem.
    Thats a fair whack of fuel use.


    Jo

  7. #7
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by pugrambo View Post
    Short of cutting your tank open and placing extra baffles in there the best thing is a surge tank
    My tank is on its last legs too.
    The longer range radar has its sights on something generic, but in the mean time, this should offer me the fuel delivery system I need at the moment, and will be a simple change over to a new tank when the budget allows.

    There are some parts of the fuego that are past their use by date and the rather flimsy (crappy) tank is becoming one of those items.


    I have a question for those more experienced in electrickary.

    How do I best power two bosh commodore pumps, located up the rear of the car???

    There is a fairly beefy power line from the new ECU out to the pump (tachometric) but that is designed for single pump system, I'm guessing.

    Should I run a new power supply back there from the battery to a relay and use the ecu power lead as the relay trigger wire and run both pumps off the relay???
    or does this sound like overkill??
    Does feeding the surge tank with a high pressure pump sound like complete overkill??
    The only reason to do that is there is a steady stream of wrecks going through this place, and low pressure pumps are uncommon as fords and I dont want to spend any more money than i can get away with.
    Jo
    Last edited by jo proffi; 10th May 2011 at 10:51 PM.

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    i realise you are economising, but if it were me, i would do this:
    *buy a tachymetric relay from an lpg fitter (ie one which shuts off if the ignition pulses stop). these cost about $100, but you really dont want the possibility of fuel spewing everywhere from a split line when the motor is stopped, but the ignition is on. particularly if you are upside down in the car at the time, trying to find where the hell the Hammer Of Life has got to...
    *fit the relay in the engine bay
    *run a new fused power wire from the battery/starter terminal, through that relay, to the back of the car, to run the pumps.
    *my intuition says that you should not use a high pressure pump to feed the surge tank, buty i cant quite articulate why.
    *my impression is that if you use a low pressure pump, you wont need the return line to the tank either. there is no return line on my jeep anymore, after the mechanical pump as replaced with a low pressure electric pump.

    i suppose that the fuel pump wire coming from the ECU might cut the fuel pump when the ignition stops anyway. in that case, yes run a separate fused wire from the battery/starter terminal to the back of the car. you will still need a relay, and personally, i would still put that under the hood, for easier access, and a less stressful environment for it.

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    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by alexander View Post
    i realise you are economising, but if it were me, i would do this:
    *buy a tachymetric relay from an lpg fitter (ie one which shuts off if the ignition pulses stop). these cost about $100, but you really dont want the possibility of fuel spewing everywhere from a split line when the motor is stopped, but the ignition is on. particularly if you are upside down in the car at the time, trying to find where the hell the Hammer Of Life has got to...
    *fit the relay in the engine bay
    *run a new fused power wire from the battery/starter terminal, through that relay, to the back of the car, to run the pumps.
    *my intuition says that you should not use a high pressure pump to feed the surge tank, buty i cant quite articulate why.
    *my impression is that if you use a low pressure pump, you wont need the return line to the tank either. there is no return line on my jeep anymore, after the mechanical pump as replaced with a low pressure electric pump.
    Sorry, Forgot to note the "beefy suply wire" from the ecu is a pseudo tachometric relay type fuel pump feed , so look, Saved $100 already.

    It needs a return line from the surge tank because as already established, there are fuel starvation issues so air will be being pumped into the surge tank from time to time and needs a way to escape back to the main tank.

    I think I am going to need to look at the power rating of these devices to save over wiring the car.

    Jo

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    Jo
    There is a large grey wire, that is used if you fit a trailer plug, that just normally does nothing in the rear wiring loom, perhaps that could feed another pump.

    ken

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    Jo

    At 10litres/100km you are using 100ml / km. A one km bend that would cause surge is almost unheard of.

    What i reckon you need is a is an inline 'surge' tank on the pressure side of the pump - I dunno what the fug uses as a filter but i'd try putting another filter in the line - even an old one that you had run a piece of fencing wire through. The standard one that they fit Foldens seem to have a capacity of about 150 -200 ml and if my theory is right you would finish up back on the level before the injectors were getting hungry.

    Ron
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    Quote Originally Posted by jo proffi View Post

    Should I run a new power supply back there from the battery to a relay and use the ecu power lead as the relay trigger wire and run both pumps off the relay???
    Yes. Preferably.

    I feel sure you will need to run similar high pressure pumps. I doubt the original pump could keep the surge tank supplied. But I could be wrong, as usual. VL Commodore pumps are cheap. I think they are meant to be immersed, so drop one in the tank, and one in the surge tank.

    You do, indeed, need to plumb the surge tank into the return line, as I described previously. It's all pretty simple.

    A difference in the heights of the feed and return lines shouldn't matter, unless you are managing in this way to create either pressure or vacuum in the tank. Put a hole in the filler cap to eliminate this possibility. An incentive to exit the car once it is upside down.

    Tim

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    Quote Originally Posted by Ron Boulton View Post
    Jo

    At 10litres/100km you are using 100ml / km. A one km bend that would cause surge is almost unheard of.

    What i reckon you need is a is an inline 'surge' tank on the pressure side of the pump - I dunno what the fug uses as a filter but i'd try putting another filter in the line - even an old one that you had run a piece of fencing wire through. The standard one that they fit Foldens seem to have a capacity of about 150 -200 ml and if my theory is right you would finish up back on the level before the injectors were getting hungry.

    Ron
    Ron, I get the impression you think my car is a carb car.
    It is fully modern efi system, and the fuel takes less than 2 seconds to get from the pump to the fuel rail.
    Any air that is blown into the fuel lines has just two escape options, back to the tank via the return line or out the injectors.
    Either scenario is a fail situation, as the pump, fuel injectors and pressure regulator are designed to work within spec with fuel, not air.
    God knows what the pressure reg does with air in its belly. I know what the pump does with a sniff of air... Nothing, and it screams.
    In contrast, a carb can happily ingest a high proportion of airated fuel
    So quite simply no air may enter the fuel lines.


    Jo

  14. #14
    1000+ Posts jo proffi's Avatar
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    I did a little test today by running the R25 efi fuel pump through the fuego Oe tank pickup.
    These are rather small lines for the carby pump.

    Nothing seemed to go nuts and the pump did not over heat. The fuel was flying around the tin that was being used as a test fuel tank.
    I know this is is not an internationaly recognised unit of mesurement but one I'm sure most frogers are familiar with...... if you'd drunk 2 longnecks and had as much back pressure as is humanly possible, you'd still not be able to get as much flow as what the pump was putting out, so its a decent amount.

    I ran the pump dry so it warmed up, and then stuck the inlet back in the fuel to enable flow. The pump cooled in a matter of seconds, so i suspect it will work just fine with the the small diameter lines.

    This is realy great to find out as it allows me to go back to an OE tank pickup and level sender.
    One of the most annoying and troublesome part of modifying the fuel lines has been the tank pickup.
    Having said that, I wont throw my huge one out just yet, it may still have a use if this system fails.



    Jo

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    I would've thought that the Fuego tank would probably be quite good for EFI as it has a large built in 'swirl pot' in the shape of the spare wheel cavity.

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    Quote Originally Posted by mistareno View Post
    I would've thought that the Fuego tank would probably be quite good for EFI as it has a large built in 'swirl pot' in the shape of the spare wheel cavity.
    It does serve well for getting the last few litres out of the tank, but only at close to zero G's.

    Jo

  17. #17
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    Default Surge tank

    Jo,

    I am not even close to an expert one these things, but I know a little about how some modern OE systems work. In these cars the potential for loss of fuel at the pickup is handled by having a bucket inside the tank that both the intake and return line sit in. The bucket can then contain a one way valve (or some other mechanism) to let fuel in from the tank. That way the return fuel is kept against the intake to be re-used if no new fuel is coming in from the tank (because you are cornering, sitting on a hill etc.). Seems simpler to me than a 2nd pump or surge tank unless you are doing some extreme manoeuvres that would throw the fuel out of the bucket (which can actually be more the size of a mug).

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  18. #18
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    Quote Originally Posted by Bolla View Post
    Jo,
    Seems simpler to me than a 2nd pump or surge tank unless you are doing some extreme manoeuvres that would throw the fuel out of the bucket (which can actually be more the size of a mug).
    Um, I possibly am.

    I thought and thought about that solution because it is an elogant one, but I could not work out how it was going to firstly contain the required volume on a corner, then refill itself once the car is back to lower G's.

    In the end, I concluded that the cup would still cause fuel starvation issues on low fuel levels.

    I dont do anywhere near the Km i once did, so I dont fill my tank up to full and generally run between 20 and 2 litres in my tank.
    The idiot light has been raise to come on with about 5L left in the tank. It starts flashing at around-80 so is a duel purpose idiotlight/fuel surge meter.
    This new system will allow me to actually run the main tank down to less than a litre before the car sees air at the fuel pump.

    This might not be a consideration to other people who run their tanks full most the time, but as I dont do that it becomes part of the design criteria.




    Jo

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    Budding Architect ???? pugrambo's Avatar
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    why run it so low ???

    if you keep the tank between 1/4 and 1/2 it costs you no more and saves a few headaches and the above cup design would work extremely well
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  20. #20
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    Quote Originally Posted by pugrambo View Post
    why run it so low ???
    A number of reasons.
    Sometimes I'm broke, and just run it dry then drive the truck until the price comes down whereby I put 20 or 30L in.
    Someone else always seems to fill the truck with stinky diesel.
    This petrol will last such a random time as some weeks I do 500km, other times just 50km, so if I fill it some months would see very old fuel still in the tank.
    Also, the mod'ed pickup I made years ago has a slight weep out of the electrical junction block if I fill it much higher than 1/2.



    Jo

  21. #21
    1000+ Posts jo proffi's Avatar
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    Giving a little more thought to the impending fuel pump plumbing and wiring,

    Would a relay like this be any good to power the pumps with, or is this something fancy??
    It looks decent quality and is all metal construction.
    I think it is 30 amp.



    Attached Thumbnails Attached Thumbnails Fuel system upgrades.-relay-box.jpg   Fuel system upgrades.-relay-inside.jpg  

  22. #22
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    Quote Originally Posted by jo proffi View Post
    Giving a little more thought to the impending fuel pump plumbing and wiring,

    Would a relay like this be any good to power the pumps with, or is this something fancy??
    It looks decent quality and is all metal construction.
    I think it is 30 amp.



    More than adequate for a fuel pump, use the second relay for the rest of F1?

    Just be aware that one side of both coils are connected to ground. (the green sleeved wires)

    Many ECU "sink" the load current, ie switch to ground - negative. If you have an ECU which does this you need to have access to both sides of relays coil and the relay shown will not be suitable.

    I like the black, plastic top, square Bosch plug in relays used in most Holden Commodores. These are suitable for most applications, switch 30 amps and plug into interlocking relay bases which cost $1.50 or so.

    I buy a bag of 50 terminals (silver plated are best) and crimp and fit in situ to make up the loom.

    Beware the black relays have different pin outs to the all metal relays of similar style.

    The relays cost very little from wreckers.
    Attached Thumbnails Attached Thumbnails Fuel system upgrades.-relay-1.jpg   Fuel system upgrades.-relay-2.jpg  

  23. #23
    1000+ Posts jo proffi's Avatar
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    Surge tank turned up in the mail today.
    It's a ripper, and very light weight, just over 800g.
    Its a bit bling so could probably do with a coating of under body sealer to give it a bit of stone protection and camouflage.

    Jo


    Attached Thumbnails Attached Thumbnails Fuel system upgrades.-surge-tank.jpg  

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    1000+ Posts jo proffi's Avatar
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    I have a question that I have no idea about, and a few searches have not yielded any hard info.

    It pertains to fuel pressure regulator location relative to the fuel rail.

    I notice most cars have it right near the last injector.

    What are the reasons for this? Ease of manufacture or something more scientific??

    IF it were moved along a few feet up the line towards the tank, would it make any difference to the pressure the injectors see??
    I'd imagine if the lines were rubber they would help iron out some pressure pulses but I dont know if there are any negatives apart from an extra high pressure line in the engine bay.

    Jo

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    Quote Originally Posted by jo proffi View Post
    I have a question that I have no idea about, and a few searches have not yielded any hard info.

    It pertains to fuel pressure regulator location relative to the fuel rail.

    I notice most cars have it right near the last injector.

    What are the reasons for this? Ease of manufacture or something more scientific??

    IF it were moved along a few feet up the line towards the tank, would it make any difference to the pressure the injectors see??
    I'd imagine if the lines were rubber they would help iron out some pressure pulses but I dont know if there are any negatives apart from an extra high pressure line in the engine bay.

    Jo
    I think it is more for packaging reasons.

    It has a vacuum line going to it that draws it's signal from the manifold below and by having the reg on the fuel rail, it saves having another high pressure line going through the engine bay to a remote reg.

    If you move it a few feet, you could possibly get a minute minute delay in response too.

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