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2 stroke water injection.

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 Post subject: 2 stroke water injection.
PostPosted: Tue Aug 10, 2010 5:56 pm 
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ok

so 2 stroke engines do not normally get water injection on the intake side. Water is often injected on the exhaust side to change the temperature of the exhaust gas, and thus changing the tuning of the exhaust chamber, alot like playing with the valve timing of an engine, this lets you shift peak torque around.

BUT i want to inject water on the intake side.

Most jetski engines are designed with intake systems to prevent injestion of water. Generally when water is injested by the engine, it is often highly uncontrolled and often at much greater then safe amounts. When this happens it often causes piston seizures. I beleive this is due to gross and uncontrolled amounts of water causing rapid localized piston cooling. yes no?

NOTE: nothing happens to the crank system. I beleive this is due to the operating temps of the lower end and the fact most 2 stroke marine oils are highly water resistant and the crank is entirely supported by needle and ball bearings.

What i want to do is safely inject water into the intake side of the engine, for its obviously well known benefits.
Can anyone chime in here with technical reasons or ideas why this would not work? Ideas on the seizures?

I also beleive this is why these engines enjoy gross overfueling as the extra fuel is utilized for combustion cooling as in the case of turbo engines without proper intercooling/water injection.

NOTE: i want to use PURE water injection, this is for a jetski so i would have a virtually unlimited amount of available water. no methanol or other additives please.


anyone's help or experience would be welcomed :)

sorry for any spelling mistakes or whatnot, im watching futurama at the same time as writing this

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 Post subject: Re: 2 stroke water injection.
PostPosted: Tue Aug 10, 2010 6:11 pm 
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Well um...as long as its not salt water I spose...and as long as its filtered at least a little.

I know on some racing outboards, they spray nitrous and some are run on straight alcohol (not really anymore due to safety). So I can't see how water could hurt compared to nitrous if you are concerned with the cooling effects.


How much of a benefit will you get from the water with no methanol though? I'm just curious about this one...especially since there is so much gasoline available to do the job in a 2-stroke. This is an honest question...I really have no idea how to think about this one. I know the heat capacity of water is high and all...

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 Post subject: Re: 2 stroke water injection.
PostPosted: Tue Aug 10, 2010 6:15 pm 
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Why do you want to do this? Is this turbocharged? Supercharged?

A few things to consider:

I would not use raw water without going through a filter, your engine won't appreciate dirt, debris, small animals, stray children, fish, or anything else that might get sucked up.

Also by injecting water you are essentially taking up space in the incoming charge that would normally occupied with fuel/air/oil, and water does not add to calorific properties of combustion.

Water injected into a N/A engine won't be as much of a benefit as a turbo engine as the intake temps aren't nearly as high in a N/A motor.

Water will condense in your crankcase and could possibly reduce the effects of the lubricating oil as well as corrosion. Operating temps of most raw water cooled 2 strokes aren't enough to boil off water.

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 Post subject: Re: 2 stroke water injection.
PostPosted: Tue Aug 10, 2010 6:23 pm 
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I know a little about 2 stroke theory. Id stay away from putting anything else in rather than fuel and premix.
My advise: take the motor out and have it ported matched to a certain pipe+carb. Someone must already have experience tuning whatever twostroker you have.

The machine work and parts will cost money but it will net you the results that you want :)

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 Post subject: Re: 2 stroke water injection.
PostPosted: Tue Aug 10, 2010 6:38 pm 
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scottmandu wrote:
Why do you want to do this? Is this turbocharged? Supercharged?

A few things to consider:

I would not use raw water without going through a filter, your engine won't appreciate dirt, debris, small animals, stray children, fish, or anything else that might get sucked up.

Also by injecting water you are essentially taking up space in the incoming charge that would normally occupied with fuel/air/oil, and water does not add to calorific properties of combustion.

Water injected into a N/A engine won't be as much of a benefit as a turbo engine as the intake temps aren't nearly as high in a N/A motor.

Water will condense in your crankcase and could possibly reduce the effects of the lubricating oil as well as corrosion. Operating temps of most raw water cooled 2 strokes aren't enough to boil off water.


Well first off 2 stroke engines are very much like supercharged engines. The exhaust chamber is utilized as a form of resonant supercharging. IF you have ever come across a comprex charged engine, its EXTREMELY similar to that. an excellent example is this image.

Image

The water injection would of course be filtered (duh) and would only be injected under circumstances where necessary (past 3/4 throttle at higher rpms where the pipe is becoming fully effective.)

I am not using the water injection as a intercooling medium or way to cool the intake charge. It is primarily being used as an anti detonant. In this respect it is very similar to its usage as an anti detonant in high compression or boosted engines.

Here is the reasoning for those that arent aware. it is VERY VERY easy to get into a power range where detonation is easily capable of destroying its pistons from heat and detonation with a 2 stroke. Extra fuel is required to keep the combustion temps low enough to avoid detonation.

static compression ratio of the engine is on the order of 6.8 to one. however toss in the dynamic compression ratio and add the supercharge effect of the pipe we are working into the 10:1 to 15:1 compression ratio ranges.

All of this is very similar to boosted 4 stroke engines. An antidetonant would be extremely welcome in a 2 stroke engine.
I have looked around and have seen that nobody is using it though. I want to experiment and see what is necessary to make it work , or even if it can be done.

3B'dB3 wrote:
I know a little about 2 stroke theory. Id stay away from putting anything else in rather than fuel and premix.
My advise: take the motor out and have it ported matched to a certain pipe+carb. Someone must already have experience tuning whatever twostroker you have.

The machine work and parts will cost money but it will net you the results that you want :)


Lol i've done what i can to this engine with what everyone knows. The only thing i cannot do is have it ported further as it would require race fuel, no thankyou...

I cannot get a pipe for this motor, and I have very little interest in making a pipe for this motor. So my best bet is to improve the motors combustion efficiency with better timing and fuel usage, and water injection would allow me to do this, and run ever more aggresive porting.


if you guessed right, the first one to get this is going to be a small 2 stroke similar to a weed eater motor.

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Audi, imprisoning me, all that i see, absolute horror. I cannot live, i cannot die, trapped in my audi, my audi my holding cell..

1988 Audi 5ktq - 10vt Ms&s Extra <- sold then someone killed it.
1993 Audi 90q - 12vt


Last edited by the_natrix on Tue Aug 10, 2010 6:44 pm, edited 1 time in total.

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 Post subject: Re: 2 stroke water injection.
PostPosted: Tue Aug 10, 2010 6:43 pm 
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sweet, I think the only thing to do from here is try it

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 Post subject: Re: 2 stroke water injection.
PostPosted: Tue Aug 10, 2010 7:00 pm 
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I suppose I would be most concerned about it displacing the oil in the bearings.


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 Post subject: Re: 2 stroke water injection.
PostPosted: Tue Aug 10, 2010 7:08 pm 
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natrix, you gotta make a pipe. You know the benefits and how much a difference a pipe alone can make on a twostroke.
You are killing me, save the water injection for after you have the other bases covered.

The effects of porting and timing will not provide as much power as with paired with a pipe.
What kind of motor is it anyways?

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 Post subject: Re: 2 stroke water injection.
PostPosted: Tue Aug 10, 2010 7:25 pm 
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1988 Audi 5ktq - 10vt Ms&s Extra <- sold then someone killed it.
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 Post subject: Re: 2 stroke water injection.
PostPosted: Tue Aug 10, 2010 9:38 pm 
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I have built many 2 strokes, all of which I raced or still ride. The fact that you think you have to run race fuel if you port your cylinders is a misconception... You would only need to do that if you raised your base compression. Porting the cylinders will just allow more airflow in and out of the cylinder. Yes it would benifit if you did have the head cut and rechambered the squish band... but you (may have to run higher octain/race gas). It all depends on how much you raise your compression ratio. I have a friend that has 3 of these ski's and 2 of them are fully ported with recut heads and run on pump gas. The water injection sounds good but would probably end up costing you more time, effort, and possible engine failure till you got it right. Water into the intake no matter what way you look at it is going to displace all the oil it come into contact with. Essentially like pressure washing your cylinder. I have seen a few engines that the head gasket blew in turn it ended up scaring the cylinder wall and taking out the lower end bearing. First because the engine is spinning so fast that when the water entered the combustion camber it cant compress it as easy as the air fuel mix. The lower and upper end bearings are the weak point. They end up getting beat and flat spots, sometimes even breaking the cage. Second when the water hits the cylinder walls, they are so hot it instantly boils and causes detonation.
Just my 2 Cents


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 Post subject: Re: 2 stroke water injection.
PostPosted: Wed Aug 11, 2010 5:01 am 
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Racerguy381 wrote:
I have built many 2 strokes, all of which I raced or still ride. The fact that you think you have to run race fuel if you port your cylinders is a misconception... You would only need to do that if you raised your base compression. Porting the cylinders will just allow more airflow in and out of the cylinder. Yes it would benifit if you did have the head cut and rechambered the squish band... but you (may have to run higher octain/race gas). It all depends on how much you raise your compression ratio. I have a friend that has 3 of these ski's and 2 of them are fully ported with recut heads and run on pump gas. The water injection sounds good but would probably end up costing you more time, effort, and possible engine failure till you got it right. Water into the intake no matter what way you look at it is going to displace all the oil it come into contact with. Essentially like pressure washing your cylinder. I have seen a few engines that the head gasket blew in turn it ended up scaring the cylinder wall and taking out the lower end bearing. First because the engine is spinning so fast that when the water entered the combustion camber it cant compress it as easy as the air fuel mix. The lower and upper end bearings are the weak point. They end up getting beat and flat spots, sometimes even breaking the cage. Second when the water hits the cylinder walls, they are so hot it instantly boils and causes detonation.
Just my 2 Cents


I have to disagree with some of your statements. First of water injection would not promote detonation, any way you can cool the air charge or slow the combustion will prevent detonation from occuring. this is the primary method that water injection uses to prevent detonation in the first place.

water injection does not have to be introduced through the carburetors, and thus the lower end. I could potentially inject water from the transfer ports, just like how some fuel injected 2 strokes inject fuel. This would eliminate water being pumped into the lower end and avoid exposure to the bearings.

lastly with the water injection i am not going to be pumping so much water into the intake as to hydro lock it. just a very fine mist of what is needed to cool the combustion enough.

There are quite a number of tuners who build these engines to certain limits, and past that they are requiring race fuel. Yes they raise the static compression slightly, but the same compression is run on a pump gas engine as it is on race gas engine. It would seem that the ignition timing, and port timing are altered to a point of requiring race fuel.

can someone please explain to me why aside from water in the lower end of the engine, even people here are seemingly against water injection on a 2 stroke where as on a 4 stroke they are gun ho to do it ?!? what is the difference if you eliminate the rotating bottom end? a piston in a bore. why in the world would it be any different from a 4 stroke to a 2 stroke at that point?

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Audi, imprisoning me, all that i see, absolute horror. I cannot live, i cannot die, trapped in my audi, my audi my holding cell..

1988 Audi 5ktq - 10vt Ms&s Extra <- sold then someone killed it.
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 Post subject: Re: 2 stroke water injection.
PostPosted: Wed Aug 11, 2010 7:27 am 
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Water injection has been awesome in any combustion engine I have ever experienced, so I do not see why injecting it in the transfer ports would be any different in the 2 stroke realm. I say go for it.

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PostPosted: Wed Aug 11, 2010 7:34 am 
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I don't see this giving you any performance benefit. It might help if it's used to mask bad fuel control. I'd try to get better control of the A/F ratio of the engine in general and skip the water injection.

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 Post subject: Re: 2 stroke water injection.
PostPosted: Wed Aug 11, 2010 8:01 am 
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I'd look at running an alcohol.water mix it's a far better anti-detonate than just water and it adds to the calorific value of the fuel.

I really don't know if the added ignition timing of less detonation would yield much considering the effort, intake temps won't drop appreciably. I guess more experimentation would be required.

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 Post subject: Re: 2 stroke water injection.
PostPosted: Wed Aug 11, 2010 10:54 am 
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Porting doesnt have to change your port timing, that is unless you want to raise your exhaust and transfer ports. Mainly its just to increase the amount of air the engine can take in. In most cases it will actully make the power broader and smoother than an engine with a real peaked out power band. The main difference with doing between doing water injection on a 2 vs 4 stroke is the lower end. On the 4 stroke the combustion chamber is technically sealed off from the lower end buy the rings. Even if you inject through the transfers your most likely going to have water start to condensate in the lower end pushing the lubrication out of the bearings. If your really gun ho to try it go for it, I just think there are better ways to make power.


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 Post subject: Re: 2 stroke water injection.
PostPosted: Wed Aug 11, 2010 2:28 pm 
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My initial knee-jerk reaction is that the fuel also lubricates the bottom-end, water does not lubricate very well. But I'd love to be proven wrong. :D

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 Post subject: Re: 2 stroke water injection.
PostPosted: Wed Aug 11, 2010 6:15 pm 
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Lord_Verminaard wrote:
My initial knee-jerk reaction is that the fuel also lubricates the bottom-end, water does not lubricate very well. But I'd love to be proven wrong. :D

Brendan



my thoughts exactly, 2 strokes are lubricated by the fuel you put into them(which I'm sure you're well aware of) I can see possibilities of some gains, but also some problems if something isn't done right. oil and water don't mix very well, and if you put too much water in and they whip up into a sludge, I can see possibilities of your bearings getting filled with water and seizing up over time (water being thinner than oil, can seep into smaller pores in the metal)

maybe find a way to inject it into the upper part of the cylinder, so it doesn't have a chance to screw with your bearings and such?

and because of the small combustion chamber, you'd need to be extremely careful to not put too much water in and end up hydrolocking/bending/snapping/screwing up things, so i'd say start off small (very small) and work your way up. and come up with an effective way to measure the gains/losses, last time I checked they don't make a jetski dyno

if anyone can pull it off, it's you.

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 Post subject: Re: 2 stroke water injection.
PostPosted: Wed Aug 11, 2010 7:36 pm 
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Direct water injection? Its a way to avoid water being in the crankcase altogether.
I really want to see what happens, this isnt called motorgeek for nothing.

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 Post subject: Re: 2 stroke water injection.
PostPosted: Wed Aug 11, 2010 7:50 pm 
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Another note... the water molecules will displace the fuel/oil molecules when being compressed during combustion. This will cause a very poor burn when the fuel is ignited. Another point is that water creates (rust) as in your rings, bearings, crank, cylinder walls, basically anything that is chorme plated or bare metal. Even the aluminum will start to form corrosion from the water.


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 Post subject: Re: 2 stroke water injection.
PostPosted: Wed Aug 11, 2010 8:00 pm 
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Yes I suppose you could tap a nozzle in the side of the block (in what I guess is called the transfer port) and have it open onl at the bottom of the stroke, when the air/fuel mix is flowing through the area into the combustion chamber. Interesting to see the outcome of this.

A lot of good points are brought up about what water can do, but WI is used on 4-strokes everywhere without problems. Only new issue would be brought up by water traveling through the crankcase, but that is alleviated with the above solution.


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 Post subject: Re: 2 stroke water injection.
PostPosted: Thu Aug 12, 2010 8:47 am 
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for those so interested, i have yet to see water wash oil off of a coated part with low pressure.

the water amount will be minimal at maximum it will be 70% of what the fuel is consumed by the motor, as dictated by most normal 4 stroke water injection formulae.

the water will be highly atomized. and with combustion chamber volumes of 38CC and cylinder bores of 84.75mm i do not think i have much to worry about with a "small combustion chamber, you'd need to be extremely careful to not put too much water in"

TC-W3 2 stroke oil is highly resistant to being washed away by water and most soaps.

Jetski engines are quite often injesting water either through water in the hull due to intrusion, or from getting sunken. Typically this even is followed by the owner removing the sparkplugs and pumping the engine clear of injested water (large amounts). once the engine has most of the water gone, sparkplugs are reinstalled and the engine is fired up and run the piss out of to dry / boil / pump the remaining water out to prevent internal engine damage due to rusting. again this is after heavy water consumption. we are talking pints of water people, not ounces or mist.

lets see where this goes.

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Audi, imprisoning me, all that i see, absolute horror. I cannot live, i cannot die, trapped in my audi, my audi my holding cell..

1988 Audi 5ktq - 10vt Ms&s Extra <- sold then someone killed it.
1993 Audi 90q - 12vt


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 Post subject: Re: 2 stroke water injection.
PostPosted: Thu Aug 12, 2010 9:40 am 
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yeah, done the whole spark plugs holes shooting water out thing. Runs just fine after that lol

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