water injection

[Anthony]

Hi, having enjoyed a early morning blat to work in the Saab which is a turbo incidentally ( it works much better with cool damp air ! ) I was pondering water injection on the 7

 

Has anyone done this with a non-turbo car ?

 

If so, anythoughts on complexity and benefits ?

 

Dumb question, but how much water do you carry around

 

many thanks A

[Peter T]

Are you bored or something Anthony ?

There really is no serious benefits of water injection on a non Pressurised engine

 

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[Anthony]

Hi Pete

 

yep a bit bored. Just wondered if it would make a difference ! new head plans are progressing gently as well.

 

Thanks for putting me straight

 

A

[Peter T]

Guess what, i am goiung to see another Spiess engine today !

Still it might turn out to be another lemon

Car finished yet, well if not hurry up as SUMMER IS HERE 😬 😬 😬

 

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[Bill Shurvinton]

Yes,

 

Pioneering research done by Sir Harry Ricardo back in the 40's with Merlin engines. Allows you to either

a) make more power

b) Use less fuel

 

For NA engines there are also combustion benefits as the water speeds the reaction of CO to CO2, increasing the power to the stroke when the mechanical efficiency of the crank is higher.

 

Its knock resistance will allow you to run higher compression, and the cooling effect gets you a denser charge.

 

You also have a nice clean engine internally.

 

 

However the gains have usually been considered outweighed by the additional complexity for NA applications. For example some research in the USA showed a 2-3% torque increase using water injection and ion sensing ignition that could correct for the water. Fuel savings would be in the 10-20% area.

[Anthony]

Thanks Bill/Pete

 

Pete, getting there on the car - big target to get car to Curry and Rollers with Ammo, providing divorce does not get in the way

 

Bill, is the water injection a constant or variable amount please ? Assume it is adjusted via throttle pot, but only guessing.

 

Regards

[Foxy Smith]

My physics teacher at high school way back then had a beautiful jaguar saloon car and a "hot" Austin A40 which looked completely standard. The A40 was used as a mobile test bed for all sorts of experiments and oneof these was water injection. To the best of my memory he used hypodermic needles inserted through the thickness of the head gasket. The water injection control was totally passive with non return valve in the lines. Metering the water was achieved by varying a restriction in the feed lines. I'm pretty sure he said that he did not feel there was a significant increase in performance but the full economy was astounding. Happy days!

[Bill Shurvinton]

depends what you are trying to do. At the simplest level windscreen washer jets can be used if you just want cylinder cooling at WOT. If you want to explore the limits then you need a fully mapped system. The ECU I use has 2 tables in, which can either be used for another set of injectors or water injection.

 

And if you want cruise economy you could use the manifold vac and it would work automagically.

[Jason Plato]

On K of course , water injection is sometimes offered as standard although it can often be contaminated with coolant .......

 

 

[Paul McKenzie]

Nice one, Dave 😬

[Joe 90]

David Vizard points out quite succinctly in his books that it's worth remembering that water puts fires out, just ask the fire brigade. As such, it will never give you more power than the engine is capable of anyway. It's best use is as an anti-detonation technique, allowing you to run a higher compression ratio. The higher compression ratio gives an economy improvement, and running closer to detonation can give a power increase. Modern ECUs with knock sensors would really be required to make the best use of it, but they would normally retard the spark to conteract detonation.

 

*thumbup*Back on the roadhere

[Bill Shurvinton]

Oliver,

 

Sorry thats ROT. Please see below a nice summary of what water does during combustion. Dave Vizard is a good bloke, but is no Ricardo, Heywood or Olsen.

-------

Let us take a quick look at ignition. The first thing that happens is a plasma

cloud is formed by the arc consisting of super heated electron stripped atoms.

When this cloud "explodes" a ball of high energy particles is shot outward.

 

The highest energy particles are the hydrogen atoms - and they penetrate the

charge about 5 times as far as the rest of the particles. As they lose energy

and return to normal temps - about 5000 k - they begin to react chemically

with any surrounding fuel and oxygen particles. The effectiveness of spark

ignition is directly related to the availability of free hydrogen. Molecules

containing tightly bound hydrogen such as methanol, nitromethane, and methane

are far more difficult to ignite than those with less bonds.

 

During combustion - water - H2O ( present and formed ) is extremely active in

the oxidation of the hydrocarbon. The predominate reaction is the following:

 

OH + H ==> H2O

H2O + O ==> H2O2

H2O2 ==> OH + OH

Loop to top and repeat.

 

The OH radical is the most effective at stripping hydrogen from the HC

molecule in most ranges of combustion temperature.

 

Another predominate process is the HOO radical. It is more active at lower

temperatures and is competitive with the H2O2 at higher temps.

 

OO + H ==> HOO

HOO + H ==> H2O2

H2O2 ==> OH + OH

 

This mechanism is very active at both stripping hydrogen from the HC and for

getting O2 into usable combustion reactions.

 

Next consider the combustion of CO. Virtually no C ==> CO2. Its a two step

process. C+O ==> CO. CO virtually drops out of early mid combustion as the O

H reactions are significantly faster and effectively compete for the available

oxygen.

 

Then consider that pure CO and pure O2 burns very slowly if at all. Virtually

the only mechanism to complete the oxidization ( Glassman - Combustion Third

Edition ) of CO ==> CO2 is the "water method".

 

CO + OH ==> CO2 + H

H + OH ==> H20

H2O + O ==> H2O2

H2O2 ==> OH + OH

goto to top and repeat.

 

This simple reaction accounts for 99% + of the conversion of CO to CO2. It is

important in that fully two thirds of the energy of carbon combustion is

released in the CO ==> CO2 process and that this process occurs slow and late

in the combustion of the fuel. Excess water can and does speed this

conversion - by actively entering into the conversion process thru the above

mechanism.

 

The peak flame temperature is determined by three factors alone - the energy

present and released, the total atomic mass, and the atomic ratio - commonly

called CHON for Carbon, Hydrogen, Oxygen, and Nitrogen. The chemical

reactions in combustion leading to peak temperature are supremely indifferent

to pressure. The temperatures and rates of normal IC combustion are

sufficient to cause most of the fuel and water present to be dissociated and

enter into the flame.

 

As can be seen above, water is most definitily not only not inert but is a

very active and important player in the combustion of hydrocarbon fuel.

Ricardo and others have documented that under certain conditions ( normally

supercharged ) water can replace fuel up to about 50% and develop the same

power output, or that the power output can be increased by up to 50% addition

of water. This conditions were investigated by NACA and others for piston

aircraft engines. It is important to note that these improvements came at the

upper end of the power range where sufficient fuel and air was available to

have an excess of energy that could not be converted to usable pressure in a

timely manner.

 

[charlie_pank]

This is almost certainly a stupid question, but a genuine one...

 

Why don't we just mix our fuel with water then? - What do we need to mess about with another injector for?

 

 

C

[Peter T]

Oh forgot to say water is very refreshing to drink 😬

Bill are you a scientist 🤔

 

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[Bill Shurvinton]

 

Engineer.

 

Water and fuel don't mix for a starter. the fuel floats on top. Secondly standard fuel injectors tend to not be made from stainless, so rust up in short order when faced with water. Stainless injectors are available.

[charlie_pank]

So the answer is stainless injectors and a method (chemical or mechanical) for emulsifying the solution? - probably mechanical as I suspect some of the advantages of water injection are precisely because of the surface tension etc...

 

Edited by - charlie_pank on 23 Apr 2004 15:47:19

[robbieclark]

I suppose if you use ethanol or methanol you can add water to the fuel as it is miscible with water.

[Joe 90]

But getting back to realistic applications, the situations investigated by Ricardo where there was a significant power increase do not exist in a NA car engine. This is why water injection is a favourite of the snake-oil salesmen. It can produce more power, but only in certain carefully controlled circumstances. If you have to ask the question, then you're not in a position to benefit from it.

 

*thumbup*Back on the roadhere

[Peter T]

Is'nt that what i said in the first place

 

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[Marius]

Peter, if you´re really interested in a Spiess-engine drop me a mail. I know someone who could provide you with a genuine one. The ones I found on the internet or at some engine builders were all not revised by Spiess...

 

Marius

 

[Peter T]

Marius i will do that, located some real JUNK and so called Spiess units, willing to pay the money 😬

 

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[Bare]

Hmmm... I have an Aquamist water injection system in my Saab.. it allows 20psi of boost.. safely... 25 is possible, but my transbox is kinda pricey :-)

As far as I know (or care:-) it lowers combustion temps enough to prevent knock at hi boost levels .. thereby keeping the ECU from turning down the boost.. and really pissing me off.

Best "go faster" Mod I ever made onna Saab :-)

A silly question remains??

IF water is so good in a NA engine, as Claimed.. why is it not incorporated into Auto molbile fuel systems.. There ain't even ONE such available example.. are all those legions of 'engineers' simply educated to a lesser standard ?

[Nifty]

To return to the remark earlier, "why don't we just find a way to mix water and fuel? ", we have......injection in the cylinder to create a fine mist, a suspension mixture of water and fuel.

 

To the remark about David Vizard pointing out that water puts fire out....try lighting a bowl of cornflour... not easy. However, cornflour dust is a great hazard because it can become explosive when created into an electronically charged dust. Mills etc have to take great care to earth all conveyors etc and keep dust levels to an absolute minimum.

i.e. compounds react very differently under varying circumstances and comparing pouring gallons of cold water onto a fire with injecting a fine mist into a very hot and pressurised container would be to compare chalk and cheese.

 

Keep off the straight and narrow 😬

 

Edited by - Nifty on 24 Apr 2004 20:54:10

[Red SLR]

I am sure one particular BTCC team used water injection on their NA engine.........