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Anyone here ever tried it? I worked at a place in the mid seventies and the MD had it done on his car which was a Daimler Sovereign 4.2 and surprisingly it was very good.

I've looked on tinternet at modern systems and they all seem to pipe cold water straight to the inlet manifold, they put some form of jet in the pipe to limit the flow and use inlet vacuum to suck the water into the engine. The idea is the high vacuum and small jet size combine to vapourise the water as it enters the manifold.

The bloke who modified the Daimler used a different technique altogether. He used an old BL plastic header tank (Marina I think) The water was then piped into an old SU carb float bowl. From there he used small bore stainless tube and removed and drilled two holes in the Daimler exhaust manifold. He then tapped the holes and used some type of plumbing fittings which screwed into the prepared holes. He then pushed as much pipe into the exhaust manifold as he dared, in one fitting and out the other and simply tightened the fittings onto the pipe to produce a gas tight seal. The business end of the pipe was simply fed into the air cleaner downstream of the filter. The result was a superheated steam fed more or less straight into the engine. Emissions were virtually nothing and performance and mpg were greatly enhanced.

He even contacted Leyland at Longbridge to try and get them interested but they didn't want to know. He used to run round in a Mini Countryman (remember them?). He had also done the mod on the mini and the local paper, The Express and Star actually did a full page spread on this fellow and road tested the car. He picked up their motoring correspondent early one morning filled it to the brim at the nearest petrol station (£3.20 I think! rolleyes.gif ) then the guy from the paper took over. He drove it hard to the coast and back then did some mixed town and country driving around Stratford and Warwick then came back through the middle of Birmingham and onto Wolverhampton then topped the tank back up to the brim. He was totally amazed that this car had been doing nearly 100 mpg and also noticed that power was way up on the standard car.

Now that I've bought a petrol BX I've been toying with the idea of trying it out. I wouldn't go so far as drilling the exhaust manifold but maybe wrap some cupro nickel pipe around it for similar results.
I do remember this type of system in several different forms, the water injection shortly gave way to the steam injection system, the idea being, I seem to remember, that the water vapour rapidly expanded after ingnition to increase the compression pressure. I do seem to remember some test done by the motoring magazines of the time with quite favourable results. Whether it was abandoned because of unreliability or purely the relativly low cost of fuel then, I don't know, but it might well be worth experimenting with.

BL not being interested reminded me of something. I used to do diesel conversions using Perkins 4/108 engines, all sorts of ingenuity was called for with different vehicles. One of the problems that arose when power assisted brakes arrived was the provision of a vacuum for the servo. The few diesel cars that were then made used a purpose designed vacuum pump, that was out of the question for me, so I devised my own system. As you will know, there is no air input restriction on a diesel, so no vacuum from the manifold when the throttle was closed, the usual way of providing it for a petrol powered vehicle. I made up a butterfly valve and fitted it in the air intake to the manifold, this was linked by a cable to the throttle, so when the throttle was closed, vacuum was supplied to the servo, directly the throttle was opened the butterfly valve would open fully. This worked brilliantly with the added bonus of quieter and smoother tickover as the compression was reduced.

When the diesel Sherpa van was introduced it uses almost my exact system, with the addition of a carburetter advance capsule to hold the valve open when the vacuum was sufficient - pity I didn't patent it! mad.gif


Very interesting. I'm not sure I understand the working principle though? What water does that improves mpg?

I have a question though, was the amount of steam sucked by the engine just self-regulated by vacuum (by the thickness of the tubing then)? Is there no need for a control system?

This reminds me the things I was reading and seeing on youtube lately -they even sell those "devices" on ebay now- where people hydrolise water to get hydrogen (or hydroxy?) which they then drive in the manifold, also by vacuum. Supposedly the optimum amount of hydroxy for improving combustion is no higher than 4% (by volume, I think). So how do these people know their engine is not sucking more than that? I have no idea because I didn't find anybody that tried to measure it. But I guess their devices produce actually much less than that, so all is fine. Very interesting though. I guess what they do though is overwork their alternator, so they will later pay back any gains in petrol. And from what I read, it is simply more efficient (from the energy point of view) to simply use the current available from the battery to drive an electric motor connected to the engine -just that electric motors are more efficient than hydrolysis-. But in general people that try hydrolysis cannot get that fact...

Please expand on the water issue, it's quite intriguing, even more if it can be easily applied.


Some marks of Merlin and Griffon aero engines, and the American Packard versions, had water injection. This only came into play at high throttle/boost settings when the water (actually a water/methanol mixture) was injected into the manifold after the second supercharger; the principle was that the latent heat of vapourisation was taken from the compressed air, thereby reducing the charge temperature and increasing charge density. The methanol was added to prevent freezing at high altitudes but it must have added to the power output during combustion. The object of the exercise was simply to increase power, fuel economy was not a factor.

This does not apply of course to unsupercharged/non-turbocharged car engines where the induction temperature is ambient - on the other hand of course we actually heat the inlet manifolds.

As water is not a fuel, it cannot release energy by burning so how can it reduce fuel consumption? Similarly, any increase in power can only come from releasing more energy which means burning more fuel.

I can't help feeling that if it were so simple and effective it would be fitted to every engine in the country, particularly with the current emphasis on fuel economy. Unfortunately, as with every mechanical process and especially hydrolising water to produce fuel, entropy rears its ugly head. ie you only get out a proportion of the energy you put in. Can anyone explain how water or steam injection gets out a higher proportion?

Hi George,

Bearing in mind this was over 30 years ago I seem to remember the stainless tubing was about the same diameter as standard brake pipe (3/16"?). The system worked well because I witnessed it. One header tank of water lasted quite a few hundred miles. No control system at all, once the water boiled it ran itself. The amount of water entering the tube was controlled by the float in the SU float chamber.

It took about 4-5 hours to install including removing the exhaust manifold to drill and tap. I should think by winding the pipe around the manifold it would be much quicker and still be able to boil the water. The idea comes from the fact that the steam or moisture does in fact make the charge more dense thereby increasing the compression. It was used extensively in Formula One. I don't know if it still is.

Interesting Peter I like your logic in fitting the butterfly.
With my Morris Minor conections I have seen this done in an even simpler way:

A second washer bottle was arranged to drip water down a copper pipe (2-3mm bore). This pipe was simply wrapped around the exhaust manifold where the water is heated to steam. The open end of the pipe is then arranged to squirt the steam into the mouth of the carburettor. I don't know how well it works but looks OK.

As the mouth of the pipe is above the water level when there is no heat (engine off) the water (steam) flow stops.

I understand also that in high boost situations on Turbocharged engines water injection can be used to prevent detonation.

biggrin.gif (Quote)As water is not a fuel, it cannot release energy by burning so how can it reduce fuel consumption? Similarly, any increase in power can only come from releasing more energy which means burning more fuel. (Quote)

Surely water, when heated in an engine, is a fuel, as water is two atoms (?) of Hydrogen and one atom of Oxygen isn't it? Are they not fuels for combustion?
Otherwise please explain why my diesel-engined cars run so much better in damp, misty weather than on a dry day! biggrin.gif
On a wet misty day the air is cooler thus more dense, so for a given volume you have more oxygen, similar in principle to an intercooler on a turbo. Maybe that's the principle on which the water injection works?

Hydrogen technology doesn't work. Its contrary to the laws of physics. You cant get something for nothing, its always going to use more energy to extract the hydrogen/oxygen from water than it can generate. As a means of propulsion, yes, its good, but only if you can produce the hydrogen from renewable sources. The only way you can get energy from matter is by a chemical reaction - oxidisation (burning) or by changing its atomic structure - dangerous - Chernoble?

terry g
a little ,ot, but regarding the (mini countyman) i make the ,ash body kits for them,
Do you do Morris Minor Traveller wood?

A bit different to the mini as it is structural.

Back to the main subject. The water doesn't add any energy but enables the engine to extract MORE of the energy produced by the petrol/ air reaction as useful power. The exact mechanism I don't know, but may be because of better expansion of the water compared to the air or it may stabilise the reaction giving a more effective burn.


There's also this whole story of "burning water". Plently of these stories around for ordinary inventors that have "dissapeared" or "been poisoned" "from the multinationals" because they had achieved and were ready to put into production systems that would make petrol useless, you know how it goes. I've read the principle of those applications, the baseline is they use special "sparkplugs" and huge voltage to burn water. So it is a not-to-difficult engine modification. There are even some videos on youtube where people manage to ignite water mist for a moment or two....

I wish I was a chemist to be able to say "that's total crap" or "this is possible if, if, if, if...".


The water itself cannot release any energy as there is no chemical change, water doesn't react with Oxygen to form a new compound, it stays as water. If you burn hydrogen then you get energy plus water, this is what all the politicians get excited about, sadly Hydrogen doesn't occur naturally in it's pure state and has to be made by splitting water which uses energy, a lot more than you get back when you burn it. Unless they can find a cheap, low carbon way of making energy to electrolyse water then the hydrogen car is a non starter.

XM v6 sadist

As a scientist but alas not a chemist - I'll have a quick go at trying to explain this.

The water cannot be split to provide extra energy - fusing water too is basically what people have been trying to do for years with nuclear fusion (Ok deutrium rather than hydrogen if you want to be picky). Which is above and beyond the abilities of most engines, yet.

The only way you can get better mpg is by burning the petrol more efficiently and this requires more oxygen from air to get absolutely the best stiochiometric mix. More oxygen is produced by injecting cooler and/or denser air. This is why engines work better in cooler foggy mornings. Why turbos work. Why turbos +intercoolers make turbos more efficient etc... I guess that this is what water injection is trying to emulate. Alternatively direct injection engines can do this by increasing the compression ratio since they run cooler and can have a greater compression ratio than normal engines. There is a Mercedes (diesoto) engine that combines a conventional petrol engine at start up with a ultra high compression (diesel like) engine at higher revs that is ultra economical due to the high compression ratio efficiency. Oh and of course diesels do all these things too but more efficiently.

I wonder whether injecting water has never caught on simply because oil and water don't mix. Imagine having a water injection system that leaks a bit of water into your cyclinders when it's not on - not a great reciepe for long term engine reliability.

Hopefully I've explained this correctly. I'm a scientist but molecular genetics rather than chemistry is my thing.


I did say that the only reason for water injection is to reduce charge temperature and thereby increase charge density, which in turn increases volumetric efficiency. I also explained that every process, and that of course includes every mechanical process, involves energy losses and that we call these losses "entropy". Perpetual motion is a myth, you always, always get out less than you put in. All this is (or was) simple 5th Form physics.

Unfortunately, hydrogen released all its reaction energy when it combined with oxygen to form water, so water has no releasable energy and is not a fuel. This same release of energy happens when fuel, essentially a compund of hydrogen and carbon, is burnt. With a stoichiometric mixture (14.7:1) the hydrogen in the fuel combines with the oxygen in the induction air to form water and the carbon combines with oxygen to form carbon dioxide, both with a commensurate release of energy. It's rare to get a true stoichiometric mixture so there is often carbon monoxide formed. The high combustion temperature also causes nitrogen compounds to form, usualy nitrogen di and tri oxides. Oxygen is not a fuel, it cannot be burnt but it does support combustion.

Assume you are travelling along at, say, 50mph in your turbocharged XM and you switch on water injection. This will induce a greater charge per cycle, presumably the ECU will increase the fuel proportionally and you will produce more power (Note. At the expense of more fuel). This will cause you to accelerate, but you want to travel at 50mph so you reduce the throttle opening and reduce the charge and the fuel back to where it was before you initiated the water injection.

The idea of the water turning to steam and helping to push the pistons down is a no-no, the heat taken from the burning fuel to produce steam is greater than the energy released by the steam, our old friend entropy again.

I realise this is old hat to many of us, but it may help to explain why I can't see any increase in economy arising from water injection. There is only one way to improve economy, and that's to reduce entropy. That means converting more of the heat released by the combustion process into useful work.


PS. I've just gone through this process with my oil fired central heating. My old boiler used to throw out enough waste heat to keep a large douple garage/workshop at a comfortable working temperature on the coldest winter days. With the new boiler that I've installed, I can rest my hand on the stainless steel flue pipe as it leaves the boiler and it's just pleasantly warm, in fact the internal flue in the boiler is plastic.

The result is a 35% reduction in fuel used, but I've now got to find some way to heat my garage.
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