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Readneck turbo

Discussion in 'XJ Technical Chat' started by Core, Oct 26, 2015.

  1. Core

    Core Active Member

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    I have been reading and studying what turbo charges are and what they do.
    I am also aware that Yamaha did come out with a turbo model of the XJ in the past.

    I had an idea.
    Could it be possible to rig up a small compressed air canister to the carb intake and release a controlled amount of compressed air (say 2-3 bar) into them?
    Would this not be some kind of cheap hybrid between turbo and NOS?
    There would have to be some rig that converts between sealed pressure air and normal aspiration into the carbs. I can see some valve chamber that would open when the chamber is going into normal vacuum. (redneck turbo/NOS is off)

    It could look like this schematic.

    screengrab201510261010-001.jpg

    Would love to hear any feedback on this idea.
    Has it ever been tried?

    I imagined that if such a rig actually worked, one could even up the O2 content in the bottle for more oooomf.
     
  2. Alan63

    Alan63 Active Member

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    Well that's kind of the idea, a turbo is basically an air compressor, the problem with the bottle is that it's a finite supply.. When the bottle is empty after a few minutes it's just extra weight.
     
  3. Core

    Core Active Member

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    Well it only takes a few minutes to kill yourself on an XJ :eek:
     
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  4. MN-Maxims

    MN-Maxims St. Paul Minnesota

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    Pressurize the intake manifold will just blow the air fuel mix from the carbs back into the air box. I don't think your idea would do anything but lean out the intake charge and stall the engine.
     
  5. MN-Maxims

    MN-Maxims St. Paul Minnesota

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    A split second actually
     
  6. Core

    Core Active Member

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    It wouldn't be the intake manifold that is pressurised, rather another "manifold" that sits in place of the air filter, or between the air filter and the carburetors.
     
  7. Stumplifter

    Stumplifter Well-Known Member

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    It may work.
    IMHO, I would not want to be twisting a valve open, which in turn accelerates the bike, while I only have one hand on the handle bars! :eek:
     
  8. SQLGuy

    SQLGuy Well-Known Member

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    If my guestimation is correct, a 750 is going to go through about 20 cubic feet per minute of air at 1 bar and 5000 RPM. With an extra 2 bar or so of boost, that's going to go a lot quicker. A 20 CF welding bottle is small, but still pretty big to be attaching to a bike (6x6x20 inches).
     
  9. Core

    Core Active Member

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    I was thinking the setup would be similar to the classic NOS setups. i.e. an on/off switch on the handlebars would operate the main solenoid, so you keep both hands fully gripped!
    You would dial in the desired boost pressure on the regulator, and open up the tap on the bottle before hand.

    Off course the difference to NOS being that NOS itself only needs to be introduced into the air before the carbs to work because it contains more oxygen itself.
    My proposed setup would require that the air intake into the carbs is a small manifold/chamber that will deliver the higher pressure air to the carbs.
    It would need to be able to fall back to the default normally aspirated mode when the pressure boost is removed - the solenoid to the pressured air is closed.


    I have been doing yet more reading and found that a run of the mill turbo charger boost is about 20-40 pounds of boost above atmospheric pressure. Assuming about 15psi is surrounding atmospheric pressure, we are needing about 35-55 psi, or about 2.5-3.5bar
    A scuba diving compressor can pressurize a tank to 300bar.
    I am not suggesting that we fit a standard scuba diving tank to the bike, but one of these disposable MIG welding gas bottles could be enough. (we´d have to forget the "DO NOT REFILL" label) :oops:

    [​IMG]

    Thought that this updated schematic may explain my idea better....

    screengrab201510261410-001.jpg




    Haven´t done the math on the air intake volume needs yet.

    Maybe a tyre valve (Schrader type) cold be installed on the air tank so you can fill her up at the gas station for some more fun! :cool:
     
  10. SQLGuy

    SQLGuy Well-Known Member

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    I'm guessing you didn't read my response. I did do the calculations. You're looking at a tank half the size of a SCUBA tank to last you about 30 seconds of 2 bar boost. It's not the PSI that's the concern, it's the volume (cubit feet). The bottle you're showing is 110 liters = 3.9 cubit feet.

    Edit: Not to mention the difficulty of jetting for variable boost or no boost at various throttle positions. Carburetors are hard enough to adjust just for altitude changes.

    Edit 2: Not to be negative. If done right, it would work, for a few seconds. The reason nobody does this is that it's not practical to carry around enough compressed air for a worthwhile solution. Pound for pound, NOS makes a much bigger difference than air. There's plenty of air around the bike, which is why forced air through a turbo or super charger is the way to go.
     
    Last edited: Oct 26, 2015
  11. Core

    Core Active Member

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    I saw it but wanted to do the calc myself
    This is what I came up with:

    upload_2015-10-26_15-21-12.png

    I guess if I was intending to drag race, could be a solution :D
    assuming it did not blow up between my legs :oops:
     
  12. Core

    Core Active Member

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    I played with different parameters and for smaller engines, this could be a viable
     
    Last edited: Oct 26, 2015
  13. Core

    Core Active Member

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    I found a mistake in my calc.
    Now looks even worse for my XJ900 example... :(

    upload_2015-10-26_15-41-8.png
     
  14. SQLGuy

    SQLGuy Well-Known Member

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    You can actually knock the needed volume numbers down by quite a bit. The volumetric efficiency of these (or any) engines is not 100%. I actually used 30% for my calculations, though that's probably a bit pessimistic. Still, I wouldn't expect higher than 70%.
     
  15. Core

    Core Active Member

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    I now see the folly of my idea.
    Sounded good while it lasted.
     
  16. XJ550H

    XJ550H Well-Known Member Premium Member

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    red neck turbo would be a can of starting fluid hooked to the vacuum ports with the can taped to the gas tank with camo duct tape.
     
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  17. Core

    Core Active Member

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    hehehe,
    That would be much easier to test as well!!

    mmmmmm?

    Oh shit,
    Why did you give me this idea?
     
  18. ManBot13

    ManBot13 Well-Known Member

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    I think he's being facetious. The problem with getting more fuel to burn in a cylinder isn't the fuel, it's the oxidizer. You need a ratio of 14:1 to 15:1 by mass of air to fuel. Some oxidizers are more reactive by mass (NOx), or you can pump in more air (super charging). Starter fluid would just enrich the mixture.

    Note too that with more boom in the engine, the stress on the components can exceed the yield stress and the engine fails catastrophically. The XJ650 Turbo had beefed up internals to deal with the 12 psi of boost that came from the "Power up Kit." That's less than 1 bar over atmosphere. Some have boosted them up to 18psi of boost, but again, that's less than 1.5 bar over atmosphere. Plus, the compression ratio is 8.2:1, compared to 9.2:1 for normally aspirated engines.

    So if your rig worked, 2-3 bar at peak torque (with necessary fuel to react with it) would probably result in a dis-assembly of the engine before the bottle ran out.
     
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  19. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Everything downstream of the pressure source will be pressurized. The easiest way do do that without needing different carbs is to build a manifold that allows the pressure source to suck from the carb instead of blow through it. Many early supercharged airplanes did just that.
     
  20. MN-Maxims

    MN-Maxims St. Paul Minnesota

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    Ah yes figure out a way to install a supercharger, that will do it.
     

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