Why does everyone use a 6 port and a 3 port?????
a 6 port will enable you to keep the return fuel flowing which is good for keeping the air bled out of the system and the additional 3 port will enable the back flush to open a clogged filter until it can be changed or cleaned. I plan using two 3 ports, one for fuel selection and one for backflush with the running position return line being looped into the draw line and the backflush connected to the filter before the veg tank.with the selector in the diesel position and the flush in the flush position, the return fuel will backflow thru the veg filter into the veg tank. good for bleeding and quick flushing the system for shutdown
Is there a diagram of the of the setup which you describe?
I ask because the same thing can be accomplished with two 3 port valves and 6 connections rather than 9.
now chris you made me think about it again! You are right and so was I in my last post to this thread. BUT if we use your way of thinking we can have full return to both tanks without the looping in to cause possible air pockets and lots less chances for air to be sucked in or fuel leakage.And you can still hook the veg return in to make it backflush the filter if you feel the need. Just goes to show, when i put something on paper i tend to over design it! But i never did see why a 6 port AND a 3 port!
Exactly! this is what i have done with the system I have designed. I have 1/3 less hose connections, 1/4 the wiring, no return modifications, easy install with full flush and return functioning the way it was designed (Mercedes still requires some return mod but the return is not looped). Also makes electronic control and safety issues much simpler.
I am not following the ability to back flush with only 6 connections instead of 9. Unfortunately, before reading this post, I bought the 6 port valve and plan to get the 3 port in the near future.
I see how the main return line can be purged back to the veg tank with diesel by not switching the return over at the same time as the supply. I have not been able to come up with the configuration the allows the return diesel to back flush the veg filter on the supply.
What am I missing?
Why would you need to backflush the filter and supply? Anything you backflush from the filter would only return to the tank and once again end up in the filter. If your lines and filter are heated what gain would be seen from backflushing? With my set-up the feed line has a final heat exchanger just before the IP, the return line does not. The engine coolant heats the VO enough to flow in the tank and lines, the heat exchanger is very efficient and allows the VO to be heated to 180F quickly and there you go. Flushing the return line is done to more rapidly clear VO from the IP, injector lines and injectors.
When running on VO, everything after the valve is filled with VO, if you simply switch the feed to Diesel and the return line is looped the VO past the valve must go someplace in order for Diesel to take its place, since the return is looped, it must be consumed by the engine, this takes time.
If you can control the feed and return lines, you simply change both to Diesel at temp, when you want to clear the VO from the system you switch the feed line (supplying diesel) and leave the return line on VO just long enough to flush the VO out of the pump and injection system then switch it to diesel as well and shut down. The point is not to backflush, which I see as pointless, but to rapidly make the transition from VO back to Diesel. The heat exchanger makes the transition from Diesel to VO rapid. You see the pump provides much more fuel than the engine can use, this excess fuel is normally returned to the fuel tank, if you loop the return it just feeds back into the pump. (see thread on "fault in looped return design")
To this end I use two 3 way valves and have no need for a manual "backflush" valve. My system is automated and at heat exchanger temp, switches to VO and upon pressing a "purge" button clears the injection system of VO and returns to Diesel operation automatically... I have one button and all I need do is press it before shut down, if I forget I get a warning buzzer for 10sec which I can ignore (if I will be restarting shortly) or I can restart and purge which is very fast.
I follow you. This is what I got when I layed it out with two 3 port valves. I was confused about the previous post that said this design would allow the back flush of the filter.
I am glad to hear you say that this is not a desirable thing to do. I was wondering why you would want to push the trapped particles back to the VO tank, but, being new at this, I thought that there may have been a need for this feature.
I use only a single 6- port valve on my 1.6 volkswagen with a seperate tank and have no idea what all this talk about backflushing is even about? When the filter gets dirty I change it! why in the world would I backflush the crud back to the wvo tank?When I flip the switch from one tank to the other it's like nothing even changed?I have put on 1750 miles this way and have had no problems this way.Maybe my mind works to simply to understand all this backflushing garbage, but I installed this all myself, designed my own 22 gallon aluminum tank, heat exchanger,etc. and it works for me.
That's great bobo, where did you put the tank? what part of the country are you in and is the tank heated and if so, how? What is your heat exchanger like? What kind of fuel temps are you getting?
Always looking for good ideas from creative people!
I personally am still dragging on tank design. The best option seems to be an alum tank with a 1/2" pan on the bottom with coolant flowing through it. The whole coil thing leaves me a bit cold :-), what I mean is that I am not sure I like the idea of a copper coil vibrating around in my fuel and one day leaking at the connectors. Have thought about a "Hotstick" style but just does not seem like it would work in really cold climates.... The again, who shuts off a diesel in really cold climates unless they have a block heater and a electric tank heater is an easy option for severe climate use I suppose.
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