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  • would it work

    since most cng powered cars will not go 200 miles why not mount a propane tank and run a line from the liquid draw to a vaporiser than valve it in between the high and low pressure regulaters with check valves for emergency fuel as propane can be gotting most anywhere and would it comply with epa and would say a new honda car pick up the higher btu and lean the fuel rate just a thought go ahead and kick me and tell why we cant I dont mind someday I might come up with something you all cant shoot down LOL

  • #2
    Re: would it work

    Propane has almost 2 1/2 times more energy content per cubic foot than that of natural gas. You might be able to get something like this to work on one of the older fumigation cars (Cavalier?) by tricking the electronics into reducing the gas flow into the engine--most likely more trouble then it's worth. If you are going to carry CNG and propane, why not just add an additional CNG tank for the range you need? It also might upset O2 sensors and you would need to provide a fake pressure and temperature signal to the computer along with a load to simulate the coil in the HPL solenoid so that the car won't switch to gasoline. Anything is possible if you throw enough time, effort and money at it .

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    • #3
      Re: would it work

      Cowboy,
      You hit on another good one. I walked down that path with our 2005 E350 dedicated fleet to give them a limp home. I first started it as a joke, to see if I brought a dedicated-bifuel to the DMV, would the agents head explode trying to figure how to register it. I figured if you have a dedicated cng engine, just add a propane kit as a bifuel option.
      The trick is having two different fuel maps and/or ECUs. If you run it right, you could probably use the same set of gasious injectors for both. Or you could do a dual fuel rail setup like the 2003/4 Ford bifuels (post compuvalve).
      Keep up the "what ifs" bro.
      Your Friendly Nazi Squirrel Administrator

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      • #4
        Re: would it work

        I have seen your proposal run on a vehicle successfully. It was done on a mid 90s dedicated Dodge Caravan which I believe was an OBD I system. The person that did the install was one of my professors, and he claimed that he could drive from Southern CA to Santa Fe NM without stopping for fuel at all. This was accomplished with both fuel systems CNG & LPG full at the beginning of his travels. I can not remember if the LPG fuel system was a stand alone system. I know that he was quite happy with the addition of the LPG system. Back in the early conversion days this was alot easier to do because of OBD I. There were many modules that could be purchased to trick the ECU with dummy signals. I do not think this would be as easy with OBD II, and I am certain that CARB would not issue an exemption for that type of system today. If is a shame that the vehicle manufacturers never caught onto this type of system, as I think it would have changed the entire landscape of the Alternative fueled vehicle industry. It would have allowed CNG vehicles to imediately replace gasoline as the predominate fuel in the US, without having to waite for the CNG infrastructure to be put in place.

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        • #5
          Re: would it work

          OK Wellarmed, who are you, send me a PM

          I had dinner with Colin a couple of months ago, and the Caravan would have been still running except that there are some mechnaical problems with the engine. Colin is doing well and Mateo is growing like a weed.

          The short version of the CNG/LPG Dodge. It was factory CNG system. An LP tank and vaporizor was installed and the low pressure line was "T" into the low pressure cng line to the injectors. I believe a manual 3 way valve was installed to direct the gas flow. The manual low pressure LPG regulator was adjusted to get the engine running on the CNG injectors to get the proper A/F mixture on LPG.

          There was phony signals sent to the ECU; rail pressure being the main one.
          Once the cng rail pressure voltage signal was stabalized to reflect normal cng rail pressure voltage the thing ran good. As long as changes in LPG pressure change with the proper change in voltage the fuel trim will work.

          This is the simple version there is more to it .

          Take care

          Larrycng

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          • #6
            Re: would it work

            What about just hosing it in via the air intake manifold? I've seen guys that mod the pedal linkage to operate a valve for a secondary fuel as well as the intended fuel.

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            • #7
              Re: would it work

              If you go to that trouble, you might as well use of the "off shore" kits, it would be cleaner

              You would not have anywhere close to accurate fuel control and emissions would go down the tubes. The old air valve systems provide better control. They are based on air flow which is really the key; specifically the mass (weight of the air to be crude) of the air.

              Larrycng

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              • #8
                Re: would it work

                The fact is that a liquid is a better carrier of energy than a compressed gas. You can get more btus in lpg than cng, but not more than lng because ngas has a higher fuel value than propane. Given the scenario you mention, Id rather take one more step and add lng storage to your cng system.

                Still think a bifuel gasoline/cng is the only way to go... just wish there were a few more bifuel vehicles to choose from- dont like contours or cavaliers much.

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                • #9
                  Re: would it work

                  The scenario I'm talking about would be for an emergency back up. Only to be used to get back to the pump. But if there is a better way I would appreciate getting pointed in the right direction.

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