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Old 11-26-2011, 11:15 PM   #1
ontic OP
 
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water injection on an airhead.

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

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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Old 11-27-2011, 05:52 AM   #2
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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.
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Old 11-27-2011, 07:14 AM   #3
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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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Old 11-27-2011, 08:04 AM   #4
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Old 11-27-2011, 03:03 PM   #5
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Originally Posted by bereahorn View Post
Yup.

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

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

They had large air-cooled jugs sitting out in the breeze, just like BMW flat twins.
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Old 11-28-2011, 02:02 AM   #6
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Yup.

Just so the OP knows what he's getting into, here's how the big boys used to do it.
LOL, yeah, um, I was thinking something a little lower tech

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.

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Originally Posted by Rucksta View Post
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.
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) 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...

Quote:
Originally Posted by Lornce View Post
"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.
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.
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Old 11-28-2011, 05:38 AM   #7
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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
That will do for tonight.
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Old 11-28-2011, 09:38 AM   #8
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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
That will do for tonight.
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!
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Old 11-28-2011, 09:42 AM   #9
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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.
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Old 11-28-2011, 09:51 AM   #10
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Originally Posted by Wirespokes View Post

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.
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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Old 11-28-2011, 10:02 AM   #11
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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.
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...

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Old 11-28-2011, 11:12 AM   #12
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That sounds like an idea that might work fairly well.
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.
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Old 11-28-2011, 11:40 AM   #13
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Old 11-28-2011, 01:44 PM   #14
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Originally Posted by Airhead Wrangler View Post
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.
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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Old 11-28-2011, 04:25 PM   #15
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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

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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
That will do for tonight.
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