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  • Convert CNG car to propane/etc?

    Put in other alt fuel because thats the most appropriate place (I realized my other CNG questions here should have been in another forum, sorry :P )

    Since the tank is the hugest expense of a CNG car it seems when it runs out of life, and the CNG only vehicles are basically useless at that point, would it be feasible to simply convert them over to propane somehow? Propane wants the higher compression anyways and it's also a gas to mix... perhaps the computer wouldn't work or perhaps you'd have to replace the whole fuel system entirely, but say a propane Honda GX might be one way to drive it a bit longer at end of life just as a car even if it no longer has the same fuel savings/reduced wear of CNG.

  • #2
    Re: Convert CNG car to propane/etc?

    I have thought of this to I would think that a heated propane regulator set to the fuel presure spec or just a little lower as the btu is higher for propane might work you would have to feed it in after the hp regulator. also might find the fuel presure sender and find the resistance spec at normal pressure and replace it with a fixed resister of that value than you could control the lean rich by changing the presure to the fuel rail. or a ajustable resister? this could be used as a limp home deal to but would have to be valved and checked to pervent back flow from one system to the other and out there on the shaky side the dmv guy might end up in the nut hut trying to get his little tiny mind around it

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    • #3
      Re: Convert CNG car to propane/etc?

      It has been done on a mid '90s CNG Dodge caravan. It was done "right" and worked very well.

      The only problem was the DUMMY that tried to put CNG in the LP tank in the back of the van --- couldn't tell the difference between the two tanks.

      Although Lp operates at a lower pressure that CNG, the CNG tanks are NOT certified for propane

      Larrycng

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      • #4
        Re: Convert CNG car to propane/etc?

        Do you mean the other way around, that the CNG should not be put in the propane tank?
        Or propane shouldn't be put in the CNG tank?
        Or both?


        I'm wondering if computer changes are necessary or if the computer could adapt to things... I know for stoves and such (unrelated) you just use a different jet size to go from CNG to propane apparently and back again so I assume the air/fuel ratio must be different. If different injectors/carb, different piping, etc etc...

        ----

        The idea has more than just 'end of life' extended use of a CNG car, propane is available everywhere, CNG is not, in a pinch a 20lb cylender of propane might be all you need to eek a few more miles out if you could connect it up and make it usable without excessive modification to limp the vehicle somewhere.

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        • #5
          Re: Convert CNG car to propane/etc?

          "Do you mean the other way around, that the CNG should not be put in the propane tank?
          Or propane shouldn't be put in the CNG tank?
          Or both?"


          And the answer is : Both.

          Closing thread now. Stillsearching, please check your pm in box.

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          • #6
            Re: Convert CNG car to propane/etc?

            I have been toying with a tri fuel GX for some time now. We have already converted several tri fuel vehicles already, but in every case the donor vehicle already had an Auto-tronics kit in it. We have indentified that this kit doesnt car if the system is running LPG or CNG. What gave me the idea for the GX is those that talk about a rescue tank of propane. say a 5 gallon jug in the trunk that can be plugged in once the CNG ran out. But this idea to reconvert to LPG makes just as much sense. Once I get fully staffed again and we have some down time I may start this and see where it leads.
            sigpichttp://WWW.CNGMOTORS.COM
            SAVE TIME. SAVE MONEY. SAVE THE ENVIRONMENT.

            2003 Hummer H2 bi-fuel
            2000 GMC Yukon XL bi-fuel
            1999 International 4700 dual-fuel
            2007 Chevy Avalanche bi-fuel

            FMQ2-36 Fuelmaker w/ 24 GGE cascade

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            • #7
              Re: Convert CNG car to propane/etc?

              Originally posted by stillsearching View Post
              I'm wondering if computer changes are necessary or if the computer could adapt to things... I know for stoves and such (unrelated) you just use a different jet size to go from CNG to propane apparently and back again so I assume the air/fuel ratio must be different. If different injectors/carb, different piping, etc etc...
              In a vehicle fitted with carburettor it's way easier to do, but a vehicle with EFI would need some chip-tuning to avoid failures.

              As I said in a recent post in my blog, it's easier to convert a carburettor-fed vehicle because there's no need to perform electronic workarounds while an EFI-fed would require...

              Another point worth mentioning is the question of the use of biofuels , becomes even easier to adapt an old model with carburetor to run on biofuels due to less mechanical complexity, both ethanol and natural gas (in this case without the need for all those auxiliary modules designed to modify the signs that the injection control unit receives from sensors around the engine). Meanwhile, in a modern vehicle of plastic to use a different fuel specifications injection sensors were continuously shooting error codes ...
              - translated from Portuguese by Google Translate

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              • #8
                Re: Convert CNG car to propane/etc?

                I travel to Mexico, Baja California (Mexicali) about once or twice a month and I have been unable to take my 2001 CIVIC GX due to the fact that there are no CNG stations. They use what they call LP liquified propane. I'm looking into purchasing the nozzle for my vehicle and adapting the fitting that they use to fill propane tanks.

                My question are: 1. Will my fuel system be affected by the LP?
                2. Will the car run properly?
                Ps, I have throught about expanding my tanks but I do not want to alter my car with extra tanks. And that still won't solve my problem, I can easily get there and back, but after I fill in El centro I can only do minimal driving in Mexico because I can only fill in el centro and I need to do plenty of drinivn in Mexico. (Don't want to run out of gas in Mexico)

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                • #9
                  Re: Convert CNG car to propane/etc?

                  Originally posted by Lome1232 View Post
                  I travel to Mexico, Baja California (Mexicali) about once or twice a month and I have been unable to take my 2001 CIVIC GX due to the fact that there are no CNG stations. They use what they call LP liquified propane. I'm looking into purchasing the nozzle for my vehicle and adapting the fitting that they use to fill propane tanks.

                  My question are: 1. Will my fuel system be affected by the LP?
                  2. Will the car run properly?
                  Ps, I have throught about expanding my tanks but I do not want to alter my car with extra tanks. And that still won't solve my problem, I can easily get there and back, but after I fill in El centro I can only do minimal driving in Mexico because I can only fill in el centro and I need to do plenty of drinivn in Mexico. (Don't want to run out of gas in Mexico)

                  CNG is compressed CH4 methane, about 130 octane. LPG is liquid C3H8 propane, about 106 octane. Do not mix the two fuels in the same tank. To do dual fuel, for starters, suggest two complete separate fuel tank systems.

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                  • #10
                    Re: Convert CNG car to propane/etc?

                    Your regulator is set up for 200-3600 PSI. I don't thing LP would even register as it only pressurizes by gas vapor pressure going from liquid to gas in the holding tank. Also note that LP tanks are generally upright, with the valve at the top, CNG tanks are generally horizontal, so there is no way to prevent LP liquid from filling up past the height of the valve. There are also entirely different PRD's and safely devices for CNG tanks vs. LPG tanks. Not a very good combination. You really would want a Bi-Fuel CNG/Gasoline vehicle to do Mexico and back.
                    '11 Fusion Bi Fuel & FMQ2-36 VRA
                    (Former owner '09 Civic GX)

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