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  • valve lag

    Hello,

    A question for those who have a 2 tank system installed:

    How do you know when to operate the return solenoid after having operated the other valve?
    In other words, how do you know how long it takes for the fuel (be it diesel or veggy) to go from one valve to the other?
    Do you just guess or there is any type of equipment out there?
    I get the gut feel that I slowly contaminate my auxiliary tank.

    Thanks in advance
    gonzalo

  • #2
    Re: valve lag

    I read a lot about purge times and decided to test the return times on my 300D only 2 weeks ago. I found that it took only 60 seconds for the fuel to do the loop back to the return and this was just with the engine at idle.

    To test the purge time, I let the engine run till it was filled with bright red transmission fluid and then put the pickup back to bio. Again with the engine only idleing, it took less than two and a half minutes for all traces of the tranny fluid to be gone. I would imagine that when the car was driving, the fuel would be consumed at a much greater rate and the purge would be a lot faster as well.

    My suggestion to get what would be a maximum purge time would be to do the same thing with your own car. Fill the system with a different coloured fuel (You could use tranny fluid out of the bottle like I did) and then swap over and see how long it takes for the line to clear the other fuel either partially or completely. From there you would know that your purge would be a lot quicker when the car was driving along.

    If you wanted to get get real organised, there are dozens of electronic kits and schematics for building simple timers on the web. You could set one of these up so once you flicked the changeover switch, the timer would throw the return valve for the delay time you set automatically. I believe some people have also used turbo timers in a similar application. This may be easier than building a kit for those that don't have any skils in electronics but would be a fair bit more expensive than the DIY alternative.

    When it is all said and done though, all you have to do to prevent contamination in your start tank is to run it right down before you refil it so all the oil is burnt up and you are always keeping mainly pure bio or diesel in there.

    Comment


    • #3
      Re: valve lag

      Hi, I am using one valve and never really bothered my self with this issue. The amount of vegy oil that will go in the return line to the start up tank is far less than 1/4 of a cup every time you change over. So if you starting up one diesel then the return fuel won't be noticed.

      I have been running my car with this system since October 06 and never had any dramas.

      Regards,
      Fitian
      <><

      Comment


      • #4
        Re: valve lag

        Fitian,
        That photo at the top of your post sure looks like a scene from a Parramatta Rd used car yard!
        Laurie

        Comment


        • #5
          Re: valve lag

          I agree, a small amount of vege in the diesel causes no issues. The main thing to remember IS not to forget to loop on vege.
          I know it sounds easy.....and I thought, oh yeah....I won't forget! But I have forgotten a number of times.....I think 3 times emptying the vege tank to the diesel tank!! Once overflowing it!!
          I have manual ball valves for the switching and the long term plan was to install a micro-switch on the loop valve......connecting that to an idiot light on the dash.

          Another point here is I have a 12v GP heater at the point of loop. It's well worth having the system looped while warming up on diesel as this allows some pre-heating of the IP before change-over to vege. The downside is, as has been commented on before is that a GP heater will accumulate some crust-i-ness, though I''ve not encountered any issues yet.

          Lately I don't uploop the system at all. I just switch fuels. (Has a slightly longer purge time.)

          '98 Hiace Vanola 22000+km and counting
          '90 Hiace Vanola probably over 60,000km now retired

          Comment


          • #6
            Re: valve lag

            In regards to the looped return vegy line. I have a got looped back hose to the main vegy supply hose just before the FPHE in my first car. In the second car I used the main tank for vegy and used a return hose to the tank (It helps getting rid of any air in the system). I noticed there is less roughness in idling comapred to the first car. I guess someone may say you lose heat by sending the hot vegy back to the tank. But I do not think it makes any difference since there are two coils full of hot vegy oil before the IP. It is a very unnoticed amount of vegy oil that goes back any way. Actually adding some vegy oil to start up tank may add extra lubrication to the diesel or the bio. This is one way of looking at it.

            Cheers
            Fitian
            Was here
            Last edited by Fitian; 20 March 2007, 09:39 PM.
            Fitian
            <><

            Comment


            • #7
              Re: valve lag

              While on the subject of purgng and the amount of veggie going to the start tank, I have one 300D which does not like cold starting on veggie blends. (I have not quantified the extent of this, but a 50:50 will not start.) This car has the valves switched simultaneously and could deliver nearly total volume of the IP, and the FPHE and fuel lines into the start tank if purged at idle.

              When I am purging, I try to purge when at full power. At this accelerator setting (flat to the floor) there is little flow back to the start tank, because I can see that the IP inlet pressure is ~5 psi and the IP return line has a >10psi pressure relief valve, so it would be unlikely to open in these conditions. When there is no flow in the return line, there will be no fuel returned to the startup tank. The purge is fairly rapid, as the fuel consumption is highest under these conditions.
              I had a full tank of biodiesel and am now at 3/4 tank, I will report any cold starting issues if they occur.


              Regards,
              Tony
              Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

              Current Vehicles in stable:
              '06 Musso Sports 4X4 Manual Crew Cab tray back.
              '04 Rexton 4X4 Automatic SUV
              '2014 Toyota Prius (on ULP) - Wife's car

              Previous Vehicles:
              '90 Mazda Capella. (2000 - 2003) My first Fatmobile. Converted to fun on veggie oil with a 2 tank setup.
              '80 Mercedes 300D. 2 tank conversion [Sold]
              '84 Mercedes 300D. 1 tank, no conversion. Replaced engine with rebuilt OM617A turbodiesel engine. Finally had good power. Engine donor for W123 coupe. (body parted out and carcass sold for scrap.)
              '85 Mercedes Benz W123 300CD Turbodiesel
              '99 Mercedes W202 C250 Turbodiesel (my darling Wife's car)[sold]
              '98 Mercedes W202 C250 Turbodiesel (my car)[sold]
              '06 Musso Sports Crew Cab well body. [Head gasket blew!]
              '04 Rexton SUV 2.9L Turbodiesel same as Musso - Our Family car.
              '06 Musso sports Crew Cab Trayback - My hack (no air cond, no heater).

              Searching the Biofuels Forum using Google
              Adding images and/or documents to your posts

              Comment


              • #8
                Re: valve lag

                Thank you all for your comments.

                Comment


                • #9
                  Re: valve lag

                  On my landcruiser after running on veg I do 1K on diesel, but returing to the veg tank, and then 4 ks on diesel with the return to the diesel tank.

                  On the merc I have a pollack valve which changes both together, but this generally runs on diesel, or does a 400K trip on oil accasionally.

                  Remember on idling cars to flush there is a difference between flushing the pump and flushing the lines out. The merc idling for ages wont start properly, I think this is beacuse the injectors are still filled with veg.

                  Originally posted by Tony From West Oz View Post
                  I try to purge when at full power. At this accelerator setting (flat to the floor) there is.....
                  Is there any other way to drive a 300D?
                  cheers<BR>Chris.<BR>1990 landcruiser 80, 1HD-T two tank, copper pipe HE+ 20 plate FPHE, toyota solenoids and filters. 1978 300D, elsbett one tank system.<BR>

                  Comment


                  • #10
                    Re: valve lag

                    Yeah, The only time I take my foot off the accelerator setting (flat to the floor) is when I get out of the car
                    Fitian
                    <><

                    Comment


                    • #11
                      Re: valve lag

                      Originally posted by MB300D81 View Post
                      Yeah, The only time I take my foot off the accelerator setting (flat to the floor) is when I get out of the car
                      Classic!

                      And Here I was thinking it was just that my poor 'ol Helga must be all clapped out! I was actually thinking of removing the accelerator pedal and replacing it with a solenoid and an on/off switch that just kept the throttle wide open!

                      I have just got to try winding up the fuel delivery on the pump to see what difference that makes.


                      Originally posted by Captain Echidna View Post
                      Remember on idling cars to flush there is a difference between flushing the pump and flushing the lines out. The merc idling for ages wont start properly, I think this is beacuse the injectors are still filled with veg.
                      I think you have an interesting and highly significant point Chris.
                      Looking at the fuel path on the 300D, the fuel can be purged from the lines and filter completely seperate from the IP and the line supplying it. Obviously there would be an amount of fuel held in the pump but at what rate it is returned I have no idea. It would be interesting to do a test with Tranny fluid after replacing the IP return line with some clear hose to see how long it took the pump itself to clear.

                      I tried Running straight oil in my engine a couple of weeks ago. It ran fine with no heating other than the hot engine and I carefully purged the fuel system ( so I thought) with bio before shutting it off for the day. I was somewhat surprised I had trouble starting it the next morning and did wonder if the unheated oil had clagged something up. Once started it ran fine so I put it down to one of the mysteries of Helga but I think you may have hit on the explaination. The pump may take a lot longer to purge than the lines and Tony's method of change over may be just what is needed due to the fuel possibly being needed to be burnt, rather than purged.

                      Tony,
                      Are you saying that unless the supply pressure to the IP is over 10 PSI, the IP does not return any fuel and presumably just draws what it needs and has used ? This would support Chris's suggestion of the IP taking a long time to purge at idle.

                      I take it the 5 PSI supply pressure you mention is from the stock fuel pump on the ip?

                      Comment


                      • #12
                        Re: valve lag

                        David,
                        I have a 'turbo boost gauge' at the IP inlet which has vacuum and pressure scales from 30"Hg to 20 PSI.
                        I have a copy of the 200D,220D, 240D & 300D Service Manual and the rating for the fuel pump is that it will deliver a pressure of >0.9Bar. I regulatly measure >15 psi (>1.0 Bar) at idle.
                        The IP return line is fitted with a pressure relief valve, set to open at 10 PSI.
                        There is no added fuel pump in the IP, so it requires a fuel pressure in excess of 10 psi for the return line pressure relief valve to open, allowing fuel (and air) to pass to the return line.

                        I agree with Chris but the reason is that the engine uses stuff all fuel at idle, not that it doesn't return fuel. My cars return much more fuel at idle than at full load due to the lower pressure at higher flow rates. At light loads, the return fuel flow is higher than at idle.
                        Many people have a looped return which also extends the purge time.

                        Regards,
                        Tony
                        Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

                        Current Vehicles in stable:
                        '06 Musso Sports 4X4 Manual Crew Cab tray back.
                        '04 Rexton 4X4 Automatic SUV
                        '2014 Toyota Prius (on ULP) - Wife's car

                        Previous Vehicles:
                        '90 Mazda Capella. (2000 - 2003) My first Fatmobile. Converted to fun on veggie oil with a 2 tank setup.
                        '80 Mercedes 300D. 2 tank conversion [Sold]
                        '84 Mercedes 300D. 1 tank, no conversion. Replaced engine with rebuilt OM617A turbodiesel engine. Finally had good power. Engine donor for W123 coupe. (body parted out and carcass sold for scrap.)
                        '85 Mercedes Benz W123 300CD Turbodiesel
                        '99 Mercedes W202 C250 Turbodiesel (my darling Wife's car)[sold]
                        '98 Mercedes W202 C250 Turbodiesel (my car)[sold]
                        '06 Musso Sports Crew Cab well body. [Head gasket blew!]
                        '04 Rexton SUV 2.9L Turbodiesel same as Musso - Our Family car.
                        '06 Musso sports Crew Cab Trayback - My hack (no air cond, no heater).

                        Searching the Biofuels Forum using Google
                        Adding images and/or documents to your posts

                        Comment

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