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Dirt bikes and diving? Is it possible?

Discussion in 'Non-Diving Related Stuff' started by James Casteel, Nov 5, 2020.

  1. lowwall

    lowwall Contributor

    # of Dives: 200 - 499
    Location: Chicago
    1,619
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    I thought about that, but let's take a KTM 350. It's a single cylinder 4 stroke. Lets assume an average engine speed of 6,4000 rpm (half the redline), thus 3200 fill strokes per minute and an average air:fuel ratio of 13:1, so about 92% of each fill is air:

    .35 x 3200 x .92 = 1034 liters of air per minute

    Since we have liters, let's take a Euro-standard 10l 232 bar tank (which is very close in capacity to an AL80) = 2320 liters of air.

    So a bit over 2 minutes at half throttle. Don't forget to leave some reserve for the ascent :)
     
    OTF likes this.
  2. JohnN

    JohnN ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Oar--eee---gun
    2,395
    1,225
    British Columbia, either the sunshine coast or Vancouver Island. Real mountains and world class cold-water diving.
     
    D_Fresh and James Casteel like this.
  3. apenland01

    apenland01 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 25 - 49
    Location: Tucson AZ
    245
    156
    You are describing a two stroke if you use 3200. A four stroke would be 1600. Down1 = intake, up1 = compression, down2 = combustion/power, up2 = exhaust. So every 4th rpm would be an inhalation lol.....
     
  4. lowwall

    lowwall Contributor

    # of Dives: 200 - 499
    Location: Chicago
    1,619
    1,649
    The R in RPM is crankshaft revolutions. As you correctly described, an intake stroke occurs on every 2nd turn of the crankshaft.

    It's a little unintuitive because it seems like "four strokes" would take 4 revolutions rather than two. But you have to keep in mind that full trip through a piston's range of motion is two strokes (up and down), not one.

    In a two-stroke engine, a piston goes through each of its operations with every revolution of the crank.
     
    apenland01 likes this.
  5. lowwall

    lowwall Contributor

    # of Dives: 200 - 499
    Location: Chicago
    1,619
    1,649
    I just thought of an easier way to estimate air usage. Note all the following numbers are reasonable approximations. 1 gallon of gasoline = 6 lbs. Air in an Al80 = 6 lbs. Normal air:fuel mixture is around 13:1 (they tend to run a little richer than stoichiometric).

    So to burn 1 gallon of gas, you'd need to burn 13 cylinders of air. 350cc dirt bikes typically use around 2 gallons of gas per hour of riding. That's 26 tanks per hour, or just over 2 minutes per tank. Which nicely matches our earlier estimate.

    Edit: Not corrected to Note at the start of the second sentence. Lol.
     
    OTF likes this.
  6. OTF

    OTF Contributor

    # of Dives: 200 - 499
    Location: same ocean as you
    483
    658
    Will an open tank with a normal valve even drain fully in two minutes? Seems to take longer. And icing is an issue. Might need to port the valve for this. Worth it though for a two minute ride on a 50 horsepower fire-spitting DPV. Wonder what it would sound like.
     
  7. lowwall

    lowwall Contributor

    # of Dives: 200 - 499
    Location: Chicago
    1,619
    1,649
    I wonder what you'd have to do to make a gasoline DPV work? You'd have to keep water out of enclosed spaces, keep your electrical paths from shorting, keep the air in the fuel tank pressurized to ambient... We know that they've run submerged engines using snorkels so it's obviously possible.

    Once you get this all figured out, the next step is obviously nitrox to increase range. :)

    Edit: Jeep with snorkel. They swapped in a diesel which simplifies the electrical issues. You can skip to 20:00 if you just want to see and hear it drive around under 12' of water.

     
    Brett Hatch likes this.
  8. D_Fresh

    D_Fresh ScubaBoard Supporter ScubaBoard Supporter

    846
    529
    This is a great suggestion. Cold-water diving year round, plus riding in the summer and skiing in the winter....
     
    Ben_3 and James Casteel like this.
  9. Mrs. B

    Mrs. B Solo Diver

    84,223
    73,916

    Some crystal clear lakes in Westalpen? (at altitude, etc)

    A guide to scuba diving in our local lakes - The Leipzig Glocal



    beautiful-shot-crystal-clear-lake-snowy-mountain-base-during-sunny-day_181624-5459.jpg
     
  10. Mrs. B

    Mrs. B Solo Diver

    84,223
    73,916

    Lake Mohave?
     

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