water injection on an airhead.

Discussion in 'Airheads' started by ontic, Nov 26, 2011.

  1. ontic

    ontic

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    Who's done it already, who's thought about it, who wants to think about it now?:D

    The issue came up in a discussion about it potentially stopping pinging in higher CR top ends running on low octane or poor fuel. That is primarily my interest, but having googled around a bit it seems interesting in and of itself for a lot of reasons. I am not talking about the method of de-coking by water injection, but rather general running with water-injection for a range of potential benefits (may want to argue these?)

    If you haven't tried it or know of anyone who has feel free to discuss and theorize on some good possible systems to get it working on a bmw airhead (aside from talking higher CR top ends, pretty much stock with Bings in my example, but no need to limit to this). I'd be quite interested in running a little experiment or two myself but don't feel like trying to reinvent the wheel- being such an old technology certainly this has been well figured out already by people much more mechanically skilled knowledgable than I.
    Simple, effective, elegant, reliable, maintainable and reversible might be good starting points for a system...

    I don't know much about this other than what I can google and other than what I stumbled across years ago looking into my old 4x4 diesel engine, so I'll just leave it at this for the moment rather than making an ass of myself:

    Have at it,
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  2. Lornce

    Lornce Lost In Place

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    "Water Ingestion" would have been a more accurate description.

    Worked pretty well and had the side benefit of steam cleaning the combustion chambers. Not the sort of thing you can "fit and forget", mind. Requires fairly constant attention and fettling.
    #2
  3. Rucksta

    Rucksta SS Blowhard

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    Windscreen washer components and fish tank supplies would be a good place to start looking for parts
    Water can be injected upstream as far as the air filter and high pressure is not required.

    I've never done it or seen it done on a normally aspirated engine but it works well on turbo motors but they generally have much more sophisticated engine managenment systems than you'll find on an airhead.

    I'm not sure how you would determine when, how much or how long to inject water on an airhead.
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  4. bereahorn

    bereahorn Long timer

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    :lurk
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  5. Tosh Togo

    Tosh Togo Long timer

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    Yup. :D

    Just so the OP knows what he's getting into, here's how the big boys used to do it. :eek1

    Start with page 7, and see if you still want to press on... :1drink

    They had large air-cooled jugs sitting out in the breeze, just like BMW flat twins. :rofl
    #5
  6. ontic

    ontic

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    LOL, yeah, um, I was thinking something a little lower tech:lol3

    Have no worries, at the moment this is firmly located within the 'thought experiment' phase, a phase it may very well never leave.
    I was originally curious about water injection when I was looking into running my diesel 4x4 on recycled oil (two tank system), but didn't even look into the water element properly due to giving up on the whole idea because of the huge messy hassle of it all. No thanks, I'll just buy my diesel, I don't use much of it anyway.

    As has been noted by others, I have also noticed how much an engine seems to love running in a good thick heavy mist/fog.

    Cheers,
    So far I've come across two low tech versions which I've had a brief scan of, both using very different approaches, one that seems to let the vacuum in the carb suck water up a tube then out through a hypodermic needle into the carb, and the other that seems to let the vacuum in the carb suck air through an (aquarium) air stone, bubble it through water (like a bong:lol3) and then continue sucking that 'moist' air into the carb.
    In one you probably get a variable amount of small drops of water sucking straight into the combustion chamber and in the other you probably get a very tiny amount of moister air getting drawn in (along with the regular fuel air mix). Both of them seem pretty rudimentary, but are interesting for this difference being at opposite ends of the spectrum- a tiny tiny bit of slightly wetter air, or water straight in there..

    It seems that most good examples injecting water do it only at high power. (and as this is where pinging occurs for me when it happens this would be the goal)
    I wonder if it could be as 'simple' as having (kind of) a seperate carburetor- basically just another float bowl for water and another main jet for water. Would water even work like gasoline through 'another' main jet in the carb venturi? Or is it just too thick and errr... unvolatile...Would we aiming for proper vaporisation, or is fine droplets OK?

    The above example, of a main water jet, is trying to think of developing something whose on/off and stages between is basically managed by the carb (and tuned I suppose through the float level and jet size, etc.)

    Lets say that water won't be sucked out of jet comparable to fuel, another possible element could be a gravity fed system (without a float bowl) run first from a tank above the carbs, through a basic flow regulator, then to a valve that was controlled by another throttle cable (via a splitter). This could then feed into the water main jet at the carb. The idea being that at (or near) full throttle the valve starts to open, and the slightly pressurised water flows out of the main jet and is vaporised/dropletised in the venturi... things to tweak now would be, the flow regulator, when/where on the trottle position the valve starts to open and how much, and the jet size...

    For the sake of the thought experiement it would be nice to try to think of something that was: fit, turn on or turn off, and maintain... constant attention and fettling sound slightly less appealing (at least in the long run).




    cheers guys,
    don't feel shy to throw some ideas around here, I'll be the idiot in this thread.:nod
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  7. ontic

    ontic

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    Just thought I would say, this is such a funny topic to research. Cars that run on water, the '100mpg carburetors', insane efficiency and power claims, conspiracy theories and mad scientists:D
    That will do for tonight.
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  8. Wirespokes

    Wirespokes Beemerholics Anonymous

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    People thought the Wright brothers were kooks, and that crazy inventor - what's his name? Oh, Tesla - one of his minor inventions was the system that fires our spark plugs - they all thought he was nuts...

    Wonder what they thought of the guy who invented the wheel?

    Water injection isn't silly at all. And it's proven to work. It also leaves the combustion chamber spotlessly clean.

    However, it doesn't have to be complicated. We have vacuum ports for tuning purposes and water can get sucked in easily enough right there.

    My idea is a small tank tucked in behind a side cover with a solenoid valve to open or close the flow from it. Run lines to the vacuum ports. Then, at those times when pinging is most likely, open the valve.

    I've attempted to clean the combustion chambers with water in this fashion but suspect it takes a bit more than a cup or two. But from that experience I do know the engine will run this way. And it sure pumps out a lot of steam! :lol3
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  9. Airhead Wrangler

    Airhead Wrangler Long timer

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    I'd try using a pressurized water tank with a VERY fine mist head blowing into the airbox. Some of the REALLY fine mist heads consume very little water and a little bit goes a long way for cooling. Just a little will give you the cooling effect you're looking for.
    #9
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  10. mykill

    mykill odd

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    That was my initial thought as well. Maybe the installation of a restrictor/ jet/ orifice in the tubing would reduce the water sucked into the vacuum port getting it to an acceptable amount, would be the easiest and least maintenance. If this was at all worth doing.
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  11. Lornce

    Lornce Lost In Place

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    That sounds like an idea that might work fairly well.

    I hung a sports bottle in the fairing of my old '83 RS with a single line leading to a T-junction. Lines either side of the T-junction lead to the vacuum ports on the underside of the carbs. A pinch valve on the single line off the bottle controlled the flow. Adjust to suit while underway at a good clip. Too much and it'll shut the motor down.

    My initial objective was simply to come up with an easy way to keep airhead combustion chambers clean and operating efficiently. It worked really well.

    Re-routing the horrible oil-dumping crankcase vent hose out of the airbox hadn't occured to me...

    :lol3
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  12. Airhead Wrangler

    Airhead Wrangler Long timer

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    Now that I've thought about it a little, spraying into the airbox (after the filter) would still probably get the air filter wet. It might be better to spray directly into the intake tubes, but would it be ok for mist to go through the carbs? You could even use those two holes that are already in the side of the rubber bellmouths.
    #12
  13. Solo Lobo

    Solo Lobo airhead or nothing

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    Stolen from MNSTY's images:

    [​IMG]

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  14. crampfan

    crampfan Banned

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    Mounting the nozzles in the air filter box get water into the carbs also, so after the carbs is the only way. Rather than water, use cheap windshield washer fluid (alcohol/water) I have methanol injection set up on my turbocharged Subaru, the system that I use has a two stage pump that only works under heavy load (med/high boost pressures). the amount of meth injected is controlled by nozzle jets. You need to be careful not to over do it, as I have seen rings broken, and oil fouled. In extreme cases piston and con rod damage as water does not compress. My worry with an N/A carburetor engine would be pulling fluid into the intake under high vacuum, so a check valve would be needed along with a pump strong enough to overcome the check valve. I don't know about a motorcycle, but my scoobie goes thru 2 gallons in about 100 miles of spirited mountain driving.
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  15. JMforPres

    JMforPres Been here awhile

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    At first glance this seems like a crazy idea, burning water. However it does work in that you spray liquid water into the combustion chamber, then the heat of the fuel combusting converts the liquid water into steam causing expansion and thus power. You get the extra power at the expense of exhaust gas temperature, not a bad thing. This technique was used extensively in WWII airplanes as emergency power.

    Jon

    #15
  16. BikePilot

    BikePilot Long timer

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    Sucking heat out of the combustion chamber by vaporizing water might not increase power in and of itself because by reducing heat you reduce pressure in the combustion chamber. But if it lets you cram more fuel and air in their and squish it up tighter before you light it off then there could be more power to be had. If there were power from the water itself then we could all get a lot better mpg in our cages with water injection. Maybe we could, but I doubt it.

    don't turbo guys use a water-alcohol or straight methanol mixture? I'm pretty sure straight water isn't the typical way to go.

    I believe the water/emergency power thing on WWII aircraft was accompanied by more fuel, more rpm and more boost, but I could be wrong.

    It seems like it would work well on hot running air cooled motos. I've also pondered adding a methonal or water/al setup to my buell.
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  17. Lornce

    Lornce Lost In Place

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    It's used to control detonation, which enables power production. It's not actually "adding power".

    Had an old Luftmeister trubo unit that fearured an alcholol ingestion reservoir for the exact same purpose. (i think someone added photos of the Lufty set-up a few posts back?) Alcohol however, probably adds to the burn and power in addition to controlling detonation.

    As I understand it.
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  18. Lornce

    Lornce Lost In Place

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    Modern engine management of FI and ignition, in co-ordination with anti-knock sensors, have made it a little more redundant.

    Be interesting to see if they could work together?

    :dunno
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  19. HighwayChile

    HighwayChile greetings from Wa state

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    i bought a add on kit from a friend ran on a 4 barrel 327 chev, he had good results with it, I cant remember the details ( CR/octane etc) I gave the kit to another friend who has a '66 vette, sold mine , I never installed it, but it was very simple.

    those old Rolls merlin WWII engines were pretty cool, I worked on an unlimited hydroplane early 70's, ( 15 yr old oil line boy, when changing engines, i crawled inside and connected the oil lines, slimly job) the boats owner Bob Gilliam had a shit load of those still in NOS surplus crates laying about his nick name "bothell junk man " was accurate, man, 427 ford side oilers laying in the dirt, its now a high tech campus, if I only had the brains to buy some of that "junk"
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  20. crampfan

    crampfan Banned

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    With the meth set up on my Subaru, I am able to run 7-9 degs more timing at 27 lbs of boost pressure, without it I am limited to 21 lbs, and have to taper off to 17 lbs near red line, adding bunches of fuel to keep knocking in check. It works well when tuned for it.
    #20