Water Injection

[Deleted member 12676]

thanks for the much needed info.
What was your setup on the CR250? (I used to own an '89 CR250 that I completely fixed up in good condition after being totally trashed.)
I have a Suzuki 100 with an overheating problem in the summer. I'd like to put a system on it. It's battery is 6 volts.
What RPM range benefits the most from the water droplets?

 

[sbest]

The bike projects (74CR250, 74XL250, 67Dream150) were all tests of the concept after water injection showed so much promise on car engines. All were a gravity fed system with an on/off valve and a flow control valve. The point was to test compression and timing changes with the water. Not a lot of success was found with the bikes. Interestingly, water will stay in the bottom end of the 2 stroke a long time after the water was shut of. The cylinder was pulled and still contained beads of water. Timing and/or compression were increased and water was added manually to see the effect. No real gains were found. I didn't try it for cooling but I think it might have promise.

On car engines, at full throttle, full load, a 351 cid engine will take all the water a washer pump can move, no nozzle, just the hose.
It was restricted in practical use to prolong the water. Just enough was used to stop the detonation.
A 600 cid turbo diesel tractor motor can go through 4 gallons of water in a 30 second pull.

Mid-range rpm gains the most, right where you would hear spark knock.
On the 7500rpm 351C the water worked best from 3500-5500 but it wasn't turned off after 5500.
Just not really needed.

 

[HeadSmess]

so the best method on a two stroker is to get the spray bars on the transfers.... bypass the case. about the only reason to mist it first i guess.

gotta agree with water in the case... it hangs around for ages. never does any good. works fine on 4 poppers. theres something odd about watching the washer bottle spraying straight into a four barrel carb...

all the same applies regards detonation...when does it occur most? at peak load... usually at peak torque.

so when would water help? at peak load...

when you lug the thing at two thousand rpm in top gear...

it wont happen when you pull the clutch and drop to second or just rev the thing unloaded.

why doesnt it work much on a bike?

the cylinder is tiny, the flame spreads fast, woomf. combustions over before you blink. theres no little trapped pockets of hot flammable gas sudenly pressurised to the point of self ignition... especially if the head and cylinder have the perfect squish band. remember with squish bands that too wide a gap is far worse for detonation than not having one at all. or the wrong shape of gap... completely useless if they kiss the piston near the inside but leave two mm at the outer edge...

dunno each bike specifically but im guessing they were all singles or twins...

not quite the same thing happens in a four or five inch bore... that can only run at a certain rpm before disintegrating... and have far more cylinders.

more rpm cures detonation.

this still deosnt explain what happens when you go adding hydrogen peroxide to the water just a touch so the easily liberated oxygen is subdued by the excess of water left...

 

[butre]

I'd like to try hydrazine on one of these bikes. I've been studying up on hydrazine synthesis. just don't know how I'd store the stuff.

 

[sbest]

I remember watching a video of a scooter on nitrous that blew the head off when the go button was pushed.
Adding straight oxygen without some sort of buffer tends to act like a cutting torch, although I like the idea of the hydrogen peroxide. Heat buffered by cold. These little engines are a wonderful testbed for new ideas if you want to experiment. Until the head blows off!

Headsmess, you explain the theories and ideas well. The big thing is for us to just get out and try it!
These engines make it affordable to do so.

Steve

Experimenting on a well worn piston and cylinder. Things were learned.

 

[lazylightning@mail.r]

How about oxygen in an aerosol can? For 1 - 2 second bursts so nothing melts, maybe this is where water would be really important. We got 80% oxygen cans at the local drug stores for about $10. These are like 95%, but I don't know how much they cost. https://boostoxygen.com/

 

[Deleted member 12676]

sbest, it is possible that your using a drip system negated the possible added benefits of using a misting system. My thoughts on that is a drip system would only be of benefit for cooling and that it probably lowers overall power by lowering the power of the cycles that have the excess water of each drip. Better to evenly distribute the water amongst all the combustion cycles by evenly misting the water into the intake tract.

 

[sbest]

I experimented with various pour, spray and mist systems on several car engines, including "bubble bottles" that worked with vacuum to keep humid air going into the engine. Maybe it is rude to call that system useless so I will say negligible result. On the diesel imagine a 3/4" line with a hydraulic pump pushing 4 gallons of water and cutting oil into the engine in less than a minute. The 351C pictured here had a 1/4" line with no nozzle IIRC. Misting not needed if the airflow is there.

Steve

 

[HeadSmess]

even a mere wiff of pure oxygen will cause serious damaging detonation. the reactions too fast, the free radicals prior to ignition too volatile. boom. you have to seriously lower the compression ratio or change fuel to something less volatile...

nos works by adding 2/3 nitrogen. energy to break the nos up is required. the extra nitrogen cools the flame. its easier to inject a measured quantity as you need 3 times the amount.

adding water will offset the increased detonation if using pure oxygen. (or have a turbo, or run high compression ratios...or run crud fuel... or use nos... etc...)

and there you are back at peroxide being easier... no regulator, easily adjusted percentage of water to oxygen content...

remembering there needs to be some extra fuel to compensate for the increased oxygen content or youre going to melt holes in everything regardless... if it keeps firing consistently, which it wont if its already hinting on lean and your mix goes past the point of flammability...


now, as a rough bit of maths...say half a litre/min into a 5 litre engine at 5000rpm...

100ml/litre at 5000rpm.

100/5000=.02 ml, per litre of swept volume, every revolution.

its a four stroke so double that. 0.04ml.../L/rev

so now we have a 50cc engine...

thats .05 litres.

0.04ml/l x 0.05 litres...


it sounds like ive missed a few decimal places somewhere...

0.002 ml of water, every revolution.

so at 5000rpm, you should get through approx 10ml water/min....

which still equals 500ml/5L...

now that takes some precision to measure!

its easier to do on the big engines. and more worthwhile.



wow. REAL photos! done with emulsion! oh my!

 

[Deleted member 12676]

sbest, the motorcycles did not have a misting system, right?
I'd like to see for myself what the benefits are on my 100cc since it needs both extra cooling and extra power.