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Does anyone make a portable CNG tank to use if you run empty?

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  • #16
    Re: Does anyone make a portable CNG tank to use if you run empty?

    Originally posted by rtry9a View Post
    The best solution is a bifuel vehicle I keep my pickup on cng- it automatically turns to gasoline when it its time to refill. We are supposed to run occasionally on gasoline anyway to lube the valve stems.

    One idea to consider... the scba tanks used for diving/emergency (firefighting) operations. They are rated to 4500psi as I remember.
    Then you don't qualify for federal tax credits. Also a dedicated CNG system and engine works better and lasts longer. I also drive bi-fuels as I travel where I cannot get CNG, but the propane bi-fuel would be the way to go if you wanted the best of all worlds...
    2000 Escalade (option 3 conversion) FOR SALE
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    • #17
      Re: Does anyone make a portable CNG tank to use if you run empty?

      The best solution is a bifuel vehicle
      I don't think so. It's always best to design the engine for the fuel it will use the most. I know with my '99 Civic the engine has a 12 to 1 compression ratio to take advantage of the high octane characteristics of CNG. If it was bifuel, I'm sure the compression ratio would have to "dumbed down" to work with gasoline at around 9 to 1 which would reduce power and economy.

      So in this example if your 5gge tank was empty (assuming no pressure at all, I don't know what base pressure to assume here), you would only be able to give yourself a 600 psi fill... so you'd better hope that the station is pretty close!
      Hey professor, if I'm not mistaken, there is a pressure regulator on my Civic that keeps the fuel pressure to 57 psi at the injectors so 600 psi might be good for 40 or 50 miles. Anyone know what a particular pressure in the tank might be equivalent to on the fuel gauge. If full is 3600 psi, what is it near empty?

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      • #18
        Re: Does anyone make a portable CNG tank to use if you run empty?

        You can't use the bit of pressure once it's below what the engine needs to operate. 600psi might take you 20 or 30 miles. I have a little about .2gge test bottle which I used once as a portable tank and it was enough to get me home once, about 5 miles.

        You have to design the engine for whatever fuel needs the lowest compression ratio. So a bifuel car is designed to run on gasoline, and runs fine on CNG (higher 'Octane' equivalent) but just doesn't get the same mileage as the same dedicated CNG engine would.
        02 GX
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        • #19
          Re: Does anyone make a portable CNG tank to use if you run empty?

          Originally posted by freedml View Post
          You have to design the engine for whatever fuel needs the lowest compression ratio. So a bifuel car is designed to run on gasoline, and runs fine on CNG (higher 'Octane' equivalent) but just doesn't get the same mileage as the same dedicated CNG engine would.
          I drive a Volkswagen Touran bifuel. It's designed to run on CNG. To make it run on gasoline requires all kinds of tricks. Modern technology allows engines to be designed for the lower octane fuel. Fuel consumption is horrible on gasoline compared to gasoline Tourans even though most of the parts are the same. Most bifuels are still designed to be able to run on gasoline.

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          • #20
            Re: Does anyone make a portable CNG tank to use if you run empty?

            Building one isn't a problem. I've been driving CNG's for nearly 30 years. My current version uses a new style 8 GGE honda tank, 3way connector form GM (available part number in GM cavalier service man), relief valve from cavalier, P36 fill receptacle from ebay, manual shut off from honda, and dispensing hose from fuelmaker, but available on ebay. Keep your eye open for cheaper parts and it will cost you between $1000-$1500. Keep in mind a 8 GGE tank will only give your empty vehicle tank 4 GGE. I used mine to drive our GX from LA to Vancouver BC, as there's a dry gap between Northern California and Portland Oregon.
            CH-4
            2009 GX
            2000 K2500
            2002 Cavalier
            1998 Contour
            Phill powered by solar power

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            • #21
              Re: Does anyone make a portable CNG tank to use if you run empty?

              Umm CNG tanks are rated between 10,000 and 13,000 psi and the corrosive nature of natural gas would destroy a breathing tank. Not a good idea.
              2009 GX
              2000 K2500
              2002 Cavalier
              1998 Contour
              Phill powered by solar power

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              • #22
                Re: Does anyone make a portable CNG tank to use if you run empty?

                Originally posted by atikovi View Post
                I don't think so. It's always best to design the engine for the fuel it will use the most. I know with my '99 Civic the engine has a 12 to 1 compression ratio to take advantage of the high octane characteristics of CNG. If it was bifuel, I'm sure the compression ratio would have to "dumbed down" to work with gasoline at around 9 to 1 which would reduce power and economy.
                In my experience, using both fuels in the same vehicle, the difference between cng and gasoline power output (and presumably efficiency) is minimal, with whatever power advantage to gasoline. The mileage on a dedicated vehicle out of fuel is 0.0 (unless you a lucky enough to stop on a downhill slope) FWIW, an adjustable boost turbocharger would make both options more efficient in a bifuel.

                reasons:
                1. The range of all cng-only vehicles is somewhat limited- compressing a gas simply is not an efficient way to store energy. My truck has approx 12 gge, good for 150 miles under most conditions and ~200 under ideal circumstances. The ~20 gal of gasoline in reserve is good for another 350.

                2. The CNG availability (outside of socal) is not good enough to gamble on a rare fuel source being available and ready to serve. Bifuel is the only practical solution to a very serious problem. The real question is which fuels make the most sense. Propane is less available, more expensive, and has a significantly lower fuel value than gasoline.

                3. Bifuel provides the opportunity to travel outside a tight local perimeter. I use my bifuel pickup, among other things, for towing a travel trailer anywhere and anytime I want to go, only much cheaper when cng is available- ie, SLC to LA, Denver, Phoenix, where cng is mostly available, but questionable or not available in some stretches (Victorville/Barstow to Las Vegas to St George, Green River to Cheyenne, St George to Las Vegas to Phoenix).

                My 2 cents: Because I don't want to be stranded alone in the boonies, I would not seriously consider any vehicle set up to be cng only, but I really like the cng option!
                Last edited by rtry9a; 04-21-2009, 02:29 PM.

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                • #23
                  Re: Does anyone make a portable CNG tank to use if you run empty?

                  Originally posted by CH-4 View Post
                  Umm CNG tanks are rated between 10,000 and 13,000 psi and the corrosive nature of natural gas would destroy a breathing tank. Not a good idea.
                  It is not a good idea anyway... but I don't think methane (1 carbon+ 4 hydrogen atoms, chemically stable) is corrosive unless it has a lot of moisture (which is supposed to be removed) that might form small amounts of methanol or carbonic acid- the "co2" fizz in soda pop?

                  There are some reports of ethanol attacking fiberglass resins in fuel tanks. I doubt methane would come in direct contact. Most lightweight tanks have thin metal or plastic liners reinforced with composites.

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                  • #24
                    Re: Does anyone make a portable CNG tank to use if you run empty?

                    Originally posted by rtry9a View Post
                    It is not a good idea anyway... but I don't think methane (1 carbon+ 4 hydrogen atoms, chemically stable) is corrosive unless it has a lot of moisture (which is supposed to be removed) that might form small amounts of methanol or carbonic acid- the "co2" fizz in soda pop?

                    There are some reports of ethanol attacking fiberglass resins in fuel tanks. I doubt methane would come in direct contact. Most lightweight tanks have thin metal or plastic liners reinforced with composites.
                    That would be true if natural gas was pure methane, but about 15% of it is nitrogen, hydrogen sufide, and Carbon Dioxide. Sitting in the tank with a little moisture and you get corrosion. Add some microbial action and biggabaddaboom.
                    2009 GX
                    2000 K2500
                    2002 Cavalier
                    1998 Contour
                    Phill powered by solar power

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                    • #25
                      Re: Does anyone make a portable CNG tank to use if you run empty?

                      Originally posted by CH-4 View Post
                      That would be true if natural gas was pure methane, but about 15% of it is nitrogen, hydrogen sufide, and Carbon Dioxide. Sitting in the tank with a little moisture and you get corrosion. Add some microbial action and biggabaddaboom.
                      I don't think there's much difference between breathing air and CNG cilinders.

                      Most natural gas contains much less than 15% nitrogen, hydrogen sulfide and carbon dioxide. Pipeline gas does not contain significant amounts of sulfides. Check your local specifications. Dutch natural gas is really shit (L-gas), but it's not even that bad. (max 12% N2+CO2) Nitrogen is inert, so that's not a problem for the cilinder. Some countries have 2% max for CO2. More CO2 is not a real problem if you never refuel on wet gas. If your gas supplier can not guarantee a suitable dew point at 200 bar (at the minimum ambient temparature for your location), use a suitable drier.

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                      • #26
                        Re: Does anyone make a portable CNG tank to use if you run empty?

                        The following might be a solution to get you at least a couple of miles further.
                        The cylinders are made and available for CNG cooking applications for boating and are filled in an exchange program. The max pressure however is only about 2200psi.
                        But again if you are looking for an emergency 'push' to the next station..
                        http://safgas.com/index.php?action=w...70&ItemID=4058

                        for locations to exchange:
                        http://www.safgas.com/index.php?acti...ebPageID=14067

                        As mentioned earlier the only missing parts is the connection from bottle to the car.
                        Maybe by just calling this place, they may see an opportunity and come up with a solution.

                        Update:
                        Those bottles are for boating use only, not for a vehicle. NOT DOT approved.
                        Last edited by OhMyGas; 07-04-2009, 07:52 PM.

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                        • #27
                          Re: Does anyone make a portable CNG tank to use if you run empty?

                          The chicken or the egg. What should have come first? I am adament in my belief that OEM CNG vehicles should have had a dual fuel option (preferebly Propane) in the early stages of vehicle production. It is unfortunate that this discussion must even take place after having AFVs from the former big three in the market place for so long. I do feel everyones pain when it comes to the lack of fueling infrastructure, which this discussion is really about. With that being said, I cannot in good conscience support the idea of carrying a spare CNG bottle for use when your vehicle runs out of fuel. This is an inconvenience, NOT an emergency! Carrying loose bottles of compressed gases of any type, in a vehicle without identifying placards could prove to be a death sentence for any first responder who arrives on the scene of a vehicle accident. If you need extra vehicle range, then please consult a qualified technician and have an extra tank installed.

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                          • #28
                            Re: Does anyone make a portable CNG tank to use if you run empty?

                            we keep coming back folks dont want a car that cant make it to the next fuel stop and worrying about running out my mom would not even thik about cng only car and she is your average consumer and this is who we have to sell to get cng as the main fuel for cars in the usa and she is a green freak so until we mandate 500 mile range for alt fueled cars we will keep sending cash to folks that dont like us and they will hold our {vulgarity removed} in there hands and can just jerk them anytime they like and that hurts my pickup will go about 900 miles and I have never had to switch to gasoline because I could not find fuel and have traveled all over the usa so dont tell 500 miles aint doable until we do this cng will remain a joke for all but the few who think outside the box like us here and from what I can tell here most of us here cant even find the box ( what box) LOL
                            Last edited by John Mitton; 07-06-2009, 08:05 AM.

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                            • #29
                              Re: Does anyone make a portable CNG tank to use if you run empty?

                              Why don't we just go for practical? Install as many approved tanks as you want or have money for and when the fuel gauge gets down to about 1/4 tank, fill up the stinking tank -- and don't take a chance on running out of fuel.

                              Let the auto club mount a tank on their vehicle and provide fuel for those who chose not to watch their fuel gauges or are not good gamblers.

                              Larrycng

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                              • #30
                                Re: Does anyone make a portable CNG tank to use if you run empty?

                                Originally posted by larrycng View Post
                                Let the auto club mount a tank on their vehicle and provide fuel for those who chose not to watch their fuel gauges or are not good gamblers.
                                Larrycng
                                Back in 2002 , one of the rep's at EV rentals told me the Auto Club towing operator in palm springs did just that. I don't know if they still do.

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