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Lakewood's non scientific CNG GGE capacity estimator

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  • Lakewood's non scientific CNG GGE capacity estimator

    Not an automotive engineer , this is from 11 years , 4 vehicles and over 200k miles on cng. Example is 100L liquid volume cylinder , cylinder mfg stating 8 GGE @ 70 degres F. and 3600 psi. Real world usable capacity about 80% (6.5 GGE) on a fast fill , The vast majority of fills were 6-6.5 GGE , driving up to 20 miles after the low fuel light went on. The largest fill I ever got on a Honda was 7.2 gge, towed in after running out.


    http://www.afdc.energy.gov/vehicles/...ing_tanks.html
    Last edited by Lakewood90712; 01-07-2017, 07:24 PM.

  • #2
    how many psi would you have to fil a civic to to get a true 8 usable gallons out of it?

    i think 4000 psi time fill @ 70F may actually yield 8 gallons of usable fuel
    Last edited by trdscfjc; 12-21-2016, 03:19 AM.

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    • #3
      Originally posted by trdscfjc View Post
      how many psi would you have to fil a civic to to get a true 8 usable gallons out of it?

      i think 4000 psi time fill @ 70F may actually yield 8 gallons of usable fuel
      The key words here are "time fill". Probably due to a stable temperature throughout the fill. I seem to get more range on my Civic GX will a slow, "time fill".

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      • #4
        TRD and HYPER I think you are both right on target on getting the rated amount of fuel into the cylinder.

        The main reason for posting the thread is for folks new to cng to grasp the concept of rated capacity and typical fast fill. The new cng driver needs to know how rated capacity of cng should not be used in the same way as liquid fuels. When a driver fills with gasoline and diesel, you know almost exactly how full the tank is, and can use until the pickup sucks air. With cng , we all know the variables on fills, another variable is how much of that last GGE is useable before the vehicle quits.

        One of the times I ran out of fuel with my older civic GX , I waited about 20 minutes, and to my surprise, the car started, ran about a mile down the freeway, and quit. I waited a few minutes and did it a second time. The cooling effect of drawing off was lowering the pressure below the fuel rail needs Some fuel still remains. I don't recommend doing this.as lean mixture is not good for the car.
        Last edited by Lakewood90712; 12-21-2016, 09:12 AM.

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