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900 psi= how many more miles

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  • 900 psi= how many more miles

    i have a 2010 Chevy impala 3.5. How many miles can I expect out of 900 psi

  • #2
    It depends. Most GM cars stop with some residual pressure (around 200 PSI) in the tank. In addition to prevent cycling from CNG to gasoline and back, many will not restart on CNG if there is less than around 500 PSI in the tank. So if you are driving and the changeover occurs, you will get more miles of CNG range then if you have to stop and restart the engine below 500 PSI. This assumes you are discussing a bi-fuel car. The pressure in the tank is not a linear thing. There are charts to show the actual pressure in relation to percentage of tank volume.

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    • #3
      Sorry this is a dedicated aftermarket Cng car. I’ve never gone lower than 900 just want an approximate milage if possible.

      emergency kind of thing

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      • #4
        Cannot give you a good answer. Is your fuel gauge just pressure only? If it is, can you actually see the pressure? Or is it just a series of lights that tell you when you have 1/2, 1/4 etc. of fuel. Pressure is only one component of the actual volume of CNG you have in the tank. The other is temperature. Both items need to be known (pressure and temperature) to get an accurate range. The best fuel "gauges" calculate the volume based on these two values. In essence, you have more volume of fuel in a cold tank then a hot tank at a given tank pressure. If you can read the pressure accurately, check how many miles you go for each 100 PSI pressure drop you see and make a chart to give you a rough idea of how far you can go. In addition, you need to see if the aftermarket installer has any information on the lowest pressure available pressure in the tank will allow the car to run. CNG fuel rail pressure can vary between installation types. Some vehicles have lower rail pressures around 35 PSI, some have higher like 175 PSI so that would also have a bearing on the minimum pressure you could operate at. I would think in most cases you should be safe down to about 200 PSI before the vehicle shuts down, possibly lower.

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        • #5
          Hi Flavillio,

          I think you have one of the NatrualDrive dedicated Impala conversions, including the optional electronic psi dial gauge near the shifter? If so the fuel rail requires 120 psi so that is where the engine will stop. And as siai47 indicated, psi is a function of fuel in the tank along with ambient temperatures. So 900 psi will get you a tad farther if it is showing this in cold weather conditions vs. on a hot day. Note also that a nice thing about CNG is that typically the engine gives you about a 1/4 mile notice by way of lugging the engine before it completely stops.

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