Water Injection for NA Engines, any benefit? 6

[zimbali]

Hi,

Could anybody let me know if water injection can help to reduce the intake air temperature significantly in NA engines? I heard that it is mostly used in Turbocharged engines.

And if it is useful Practically, is there any way to make a DIY version on a low budget?

Engine: 1.6L, 112 BhP, compression ratio: 10.5



Cheers


You can live in your car, but you can't drive your House!

 

[patprimmer]

There have been a number of previous threads on water injection.

Please do a site search so we don't all have to do it over again.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
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[EngJW]

Go to the NACA website and dig into those great WW2 technical papers. It was widely used back then.

 

[zimbali]

Thanks Pat,

I went through the topics. As you suggested, most of the effect of WI is the story happening INSIDE THE COMBUSTION CHAMBER, where it helps to have more compression (or more advance) due to less knock.

There were also some suggestions to mix water with Methanol or Ethanol and then do the injection. Now I have a question based on these two factors:

Can I add methanol to my fuel tank instead of injecting it into the intake manifold, as we are not mainly using WI to cool down the intake temp but for knock resistance improvement.

Will there be any corossion issue with injectors by doing that?



Cheers


You can live in your car, but you can't drive your House!

 

[Warpspeed]

Water injection is not going to reduce induction temperatures, assuming the water temperature is at ambient. There is no mechanism to remove any heat from the system.

As Zimbali says, it can reduce the chances of detonation, but that is not what is being asked.

 

[patprimmer]

Water does reduce the intake charge temp, even if only slightly, and the degree depends a lot on design and length of the inlet tract.

The mechanism is latent heat of vaporisation. Alcohol, especially methanol in the water greatly increases this.

Methanol and ethanol both mix well with water, but poorly with hydrocarbon fuels, so maintaining a homogeneous mix in the tank is a problem along with corrosion in the tank and other components unless all components are of materials that resist water, the basic fuel and alcohol.

Alcohol in the fuel tank will also upset the tune of the engine as alcohols require a different air to fuel ratio than does normal petrol supplied as motor car fuel.

Regards
pat pprimmer@acay.com.au
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[kmccut]

I wrote an article about five years ago that contains many details about the development and use of water injection during WWII. If you are interested, you can find it at

http://www.enginehistory.org/Frank Walker1.pdf

Water injection works best in supercharged engines by reducing charge temperature thereby lowering the detonation margin, allowing greater manifold pressure, which results in more power.

While Frank Walker's experiments used practically no special equipment, production aircraft water injection systems were integrated with the injection carburetors and were fairly sophistocated.

Kimble D. McCutcheon
President
Aircraft Engine Historical Society

 

[Warpspeed]

While the benefits of water injection when used with forced induction are very well known, I still question if it is going to be of any real advantage in an n/a engine.

Another factor to consider is that where there is water vapor, there can be no free oxygen. In other words an engine simply would not run on pure 100% water vapor (steam) plus fuel.

As volumetric efficiency is limited, introducing an excess of water vapor may very well reduce power, even if the induction temperatures are reduced as well. None of this is an issue with forced induction because more available oxygen is being forced into the engine under pressure. An n/a engine does not have that luxury. I have never seen any test figures for water injection on normally aspirated engines, but my feeling is, that it may possibly do more harm than good to power.

Put another way, if it worked well on n/a engines, it would already probably be in fairly widespread use by now.

 

[patprimmer]

If you read the previous threads, you will see why OEM are reluctant to use water injection.

Water injection does increase power on an NA engine IF, AND ONLY IF, THE COMPRESSION RATIO IS TO HIGH FOR Available FUELS, as it reduces the tendency to detonate and allows optimum spark advance.

Regards
pat pprimmer@acay.com.au
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[zimbali]

Dear Pat,
I got your point very well. As I said at the to p of this topic, I run an engine with 10.5 compression ratio and 89 to 91 Octane. The engine is equiped with knock sensor and I strongly believe that increasing knock resistance will improve the ^performance in this case.

Anyhow, I can think of two solutions, Octan Booster kind of thing and water injection. I really don't know which can have more effect. I think Octan Booster has at least less side effect

And the longest path I could imagine for injecting point of the water, is spraying it on the air filter, but I think it might obstacle the air flow by filling the small holes of the filter. Any suggestions?


Cheers


You can live in your car, but you can't drive your House!

 

[Lou Scannon]

There was a report on work done by GM in the early 50's on various internal coolants, EGR and water among them. The work was done with a normally aspirated Olds 303 engine, and as I recall, compression ratio was one of the independent variables. They found some benefit, in terms of greater power and specific fuel consumption, with optimized spark timing for each of the coolants I believe, especially as compression ratio was increased. Still greater benefits are available for supercharged engines, of course. Judicious use of an internal coolant will permit use of a lower octane gasoline with no other changes to the engine; some loss of performance will occur in this case however due to the delaying effect on combustion, just as retarding the spark would do.

 

[irvin13143]

There is a way to demonstrate to yourself the effects of water vapor on the normal small gasoline engines , used on todays midsized sedans or trucks .
You will have some positive results, but remember these results will not happen all the time . Like many have mentioned,, Winter months can freeze water and you will not get things going again until the system thaws out .
Simply install a small Ultrasonic water mist generator upstream of the intake manifold , behind the sensors and air filter .. They vary in size and this will take some calculations , and/or engineering data to determine the best Mist generator to use . In other words engineering data along with experiamentation will determine how much Distilled Water can be used without hurting the engine .
Ultrasonic Miss Generators are Pizeo Electric Transducers ,, typically Steiner and Martin type , (Out of Florida) They have a long life of 3000 or more hours. They atomize Water ,, and it can be installed in such a way to be sucked into the intake manifold .. No re-condensing occurs in the Manifold , due to it is too hot ,a Baff plate or Mistermat can be used to be sure not to put too much Water in the system ..
The idea is to keep the manifold hot enough to super heat the atomized water , this is easily done in summer months, but not so easy in the extreme colds of the north . Down here in the south ,or Texas we use Atomized Distilled water, Mixed with ambient Air .
We do not turn on the switch to atomize the water until temperatures are up in engines , We do not run it on rainy days ,, or Extreme cold conditions .
A simple level control system Keeps the Ultrasonic Pizeo Electric Transducers covered with about 1.5 inches of water ,, so this may not work to well in severe inclines .. The system automatically shuts down on a lack of water level .
Results normally are from 10-20% increase in fuel economy, with a slight increase in Power .. Nothing is changed on the engine , except maybe making sure you have a 195 or better engine coolant thermostat .. A system like this will cost about $70-$100 to manufacture at home ,, and a few hours work .
Results vary depending upon many factors ,, and we are not PHD engineers , but back yard Novice inventors .. We simply try and find simple cost effective ways to improve Fuel economy While not destroying our expensive machines .. Atomized Distilled water cost about 50 cents a gallon , consumption ranges from 1 liter-- 4 liters per hour, on the highway. I have a 2000 Buick Lesabre , and I get ruffly an average of 35 MPG on the highway using atomized Distilled water as an aid to Regular unleaded fuel . I combine the gasoline volume , and Water volume , in liquid gallons , to come up with the correct figure .
I am employed by Shell Oil, Shell will not give me a Patent release to Patent my device , due to it will hurt their bottom line . ( though Shell Oil has had nothing to do with this invention ) Ultrasonic Mist generators can work to atomize water and increase fuel economy without hurting the engine . But it must be installed at the right location in the intake manifold . And used under the correct conditions. WE ( myself and other professional Machinist/technicians ) have done extensive research , along with engineers and are convinced the technology exist to perfect this system . Hopefully real PHD engineers one day will accept Water injection as a simple means to increase Fuel economy .
The water droplets are 1 micron in size ,, and quickly split even smaller when heated. Expansion is 1600 times .. Also we have experimented with fuels using Ultasonics for atomization , also producing 1 micron or smaller size particals , small enough to pass through Fuel injectors , then the cavitation bubbles collapse ,and aid in mixing better with Oxygen .
We are just stubborn Technicians , and are still looking to Improve our system .

 

[Warpspeed]

If anyone wants to do a search on this Google "nebuliser".

That is the medical application for creating cold "steam" by smashing up water drops using ultrasonics. Chronic asthmatics know all about these things.

 

[Deathscythe556]

Going back to the original question, is it practical on a small NA engine and can it be done on a budget, id have to say yes. I became interested on this subject several months ago and managed to construct a simple, vacuum-controlled system that is able to vary the water injection rate dependant on engine speed, using a simple vacuum-regulator valve used to control waste fuel gases to a coke chamber and several one-way and flow valves found in the local gardening centre.
System works like this:
water is first passed through a one-way valve from the tank to prevent back-flow, then to a manually operated flow valve to control the overall system, then through a T-section with another manual valve controlling air intake. I have found that the water must be mixed with air before the regulator valve so that it can be controlled accurately. Anopther one-way valve stabilises the flow into the regulator, which is itself, controlled from a vacuum take-off from the brake servo check valve. From the regulator, a short hose (2 inches long with a T-section in the centre and a reversed one-way) joins the system to the manifold intake under the throttle plate.
The water can be controlled using the manual valves to achieve certain results, either improved power, low-end torque or simply improved mpg.
The engine ive tested it on is my own workhorse of a 1.2l, and set to max torque, it can carry a 200 kilo toolbox in the boot up a steep incline as easily as if there was none!
The water in my opinion does not require to be finely dispersed in the manifold, as when the water hits the piston crown during the intake stroke, it will boil away into steam as the piston is around 500-700 degrees C before combustion and will produce intake swirl and improve fuel atomisation before ignition during this boiling. larger volumes of water will extend the flame duration, although it can under extremes prevent the engine from revving up freely, the tacho in my car will not exceed 3000rpm when set to max torque.

 

[MGaberik]

Water Injection was "popular" in the '70's when engine knock was a big problem because of low octane gasoline combined with lean factory mixture settings. Today, electronic engine controls have solved the problems.
Then you could buy water injection kits that worked off a provided engine manifold vacuum switch to introduce the water above the carburator at a predetermined engine loading(manifold pressure).
Spearco was one kit that was available if I remember correctly. The orifice installed in the aircleaner lid above the choke plate. Ads were in the back of magazines.
There was an article in Pop Sci magazine or the like with a 13:1 N/A 4 cylinder car runnning on regular unleaded using water injection to prevent detontation.
Just to clear things up:
The water injection works by the water evaporating in the intake air and cooling off the intake charge. Once vaporized, the water does nothing after this except take up room in the cylinder, hence, somewhat reducing the volumetric efficiency.
Presumably, this would allow you to add more timing or increase compression ratio and run on the same fuel under heavy load. I doubt it is worth the trouble today for anything with digital fuel injection as their are better approaches to making more WOT power.
Adding methanol to the water supply, as was done for the 1962 Oldsmobile turbo jetfire, is to prevent the supply tank from freezing in the winter, and doesn't really change or improves the effectiveness since the latent heat of vaporization for methanol is less than that of water.
Hope this helps......

 

[patprimmer]

MGaberik

If you follow my advice earlier in this thread, you might broaden your horizons a little

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MGaberik]

Sorry Pat,
However the Latent Heat of Vaporization for Water is 540 cal/gram
The Latent Heat of Vaporization for Alcohol is typically 204 cal/gram.

That is why I wanted to point out that adding alcohol to an SI engine water injection system will generally reduce it's effectiveness.

It will, however, prevent freezing. Use the smallest amount of alcohol that will keep the water injection supply from freezing to maximize the water (and intake cooling) for the lowest expected ambient temperature in service.

 

[patprimmer]

Alcohol in the water has several advantages.

It is a fuel and will slightly enrich the mixture, which might be good or bad, depending on lots of other variables.

It lowers the freezing point.

It evaporates easily.

It prevents the formation of algae in the water. The algae can block nozzles if allowed to grow.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[PEW]

Electronic engine control obviously DOES prevent detonation but it does so by retarding the ignition timing when necessary via knock sensors and/or altering fuel mixture strength by mapping.

This may not be strictly the most effective way for power; almost certainly not couple with economy where an engine should be able to run a more advanced igition/leaner mixture but detonation precludes it.

From my own research (I run a road/off road car at 12 to 1 CR) it seems to me that the way forward for best power combined with good economy is to use a very high CR, advanced ignition settings and water injection to help prevent detonation, irrespective of NA or Forced induction.

Another advantage is a cleaner engine interior; the process prevents carbon build up. I'm not a chemist but I believe emissions are improved too.

Presumably car designers don't like water injection as it overcomplicates the vehicle and needs more owner input/effort (to fill up with water as well as fuel).

Maybe in a few years we will see a water filler point next to the fuel filler cap. The price of fuel will ultimately change the way we look at things that we take as the norm today.

 

[DMan1]

Water injection is getting serious attention these days in the aftermarket (but mostly for non-NA applications).

However, if you wanted to run a high compression, high timing NA engine, I think water injection would be helpful in controlling in-cylinder peak temperatures.

MANY people have created DIY water/alcohol injection systems, including me, for use on street/drag vehicles. Simple 12V pump, lines, nozzle, and a manifold pressure switch.

Resources:
Here's a vendor with a good grasp on things. I use their nozzles.

http://www.aquamist.co.uk

Denis Kefallinos