water injection

[maximtaylor]

I know where to put it, and the answer involves hard currency OJ

If the engine bay looks full, and you still have your battery in the front take a looksie inside the nose, just under the bonnet latch. There is a huge space under there with a ledge to secure the pump onto. Only problem is going to be getting tools in there to tighten the fixings!

The holes could be drilled from underneath

Haven\'t done it yet, but I think this is where I\'ll put mine.

Regards

Max

[Archbish]

yeah, i did see that, but figured if there was somewhere else, that may be more convenient...  I might just bolt it to the underside of the bonnet!! *grin*

Cheers sweetie!!

((Now why can\'t rich be more like max - nice accomodating and helpful...  Max, You aren\'t a moderator either are you...  You know, I just got offered moderatorship on another thread, and then it was taken away from me straight away.  But they still have Rich as a moderator and not us...  strange, isn\'t it))

[Fish]

Iwan, the WI kit that Miguel is running is not the ERL system, and I wouldnt want to fit the ERL pump there due to heat from the turbo\'s.

US Non ERL Install

You could always mount the pump in the boot, but they do make a fair bit of noise and not something I would want.

Dan

[maximtaylor]

erm!

Actually I am a FDUK moderator now!

Sorry mate, its you v moderators now - you\'re on your own.

:wave

Max

[bill shurvinton]

A few notes on water injection:

Injecting at the compressor is the best place to do it. It moves the compression from being adiabatic to nearly isothermal. This is more efficient. More efficient =more HP. A fine mist, as a misting nozzle will give will not hurt the compressor blades, but if you are worried then inject into the scroll of the turbine; most of the compression occurs in this area anyway.

To get the most from the technique you should ditch the intercooler altogether and just use water for the charge cooling. This is  against the grain for many and very few tuners have done this, but the theory stacks this up thermodynamically (and tuners get to make £££ selling aftermarket intercoolers). No IC means more power again :-)

Water itself is a great thing. As well as cooling and providing knock protection it is actually very active during the combustion process and helps speed certain reactions along. I can share the chemistry if anyone is really interested.

My favourite method for WI is to use manifold pressure to pressurise a tank of water connected to a misting nozzle spraying into the compressor. Bar a solenoid to turn it on at a preset boost the only moving parts are the air and the water. Because it runs off boost pressure water flow increases with boost as you want it.  And its cheap. I like cheap  :-)

A handy little toy is http://not2fast.wryday.com/turbo/glossary/turbo_calc.shtml . It allows you to play around with water injection and see the effect that is has on power. It does not prevent silly numbers being entered, so you have to think a little

Bill

[Mike]

Bill,

I\'m following what your saying and interested to learn more, so expand further if you don\'t mind.  How do you see the compression being nearly isothermal? (digging up my engineering degree times now!) The compression is done in the housing, so are you saying inject before the housing? Surely it would be better to cool the charge immediatly after the compressor, after the work and heat energy has been put into the air, where the benefit of WI will have most effect?

I\'m confused as to why you say no IC means more power.  I understand that it will reduce lag, but can you explain this in a thermodynamic sense? and also explain the chemistry your talking about and how it can help speed up the reactions your talking about.

Cheers, interested,
Mike

[bill shurvinton]

Sorry for reply lag. Auto mailer seems to be not doing its stuff at the moment.

First off the cooling. If the water is present as the compression occurs then it cools the air AS it is compressed rather than compressing (and therefore heating and reducing the density) followed by cooling. I\'d have to go up in the roof and make my head hurt to be able to get the proof, but enough friends of mine who still do remember their thermodynamics  concur that it is a more efficient way of doing things. If you look at it in CFM terms with WI at the compressor you are gettting the same CFM, but at higher density.

On the intercooler side, there are a number of things to look at. Firstly pressure drop. Even with a big IC there will be some losses. It may be as low as 1PSI, but that is one pound less boost . Secondly you have the \'interwarmer\' syndrome. when you are off boost or at low boost the intercooler as often as not adds heat rather than removing it. Its more an efficiency thing rather than power, but efficiency is good.

ON the water in combstion side, here are some notes from a friend on the subject:

----------

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.
--------------------

What the above actually means is that WI, when treated holistically as part of the system rather than a bolt on at the end gives you more power for less fuel, which can\'t be bad.

Bill

[t2rew]

wow  

[<--rYaN-->]

lol i followed the last paragraph, and thats summed it up for me

[Mike]

Thanks for that Bill, answers some of the questions I had, but opens up many more, so I\'ll look into it further if and when I get time - interesting to apply engineering principles to such things, but I seem to have forgotten a lot since my studies.

Was kinda following the chem bit, but got confused on...

"consider that pure CO and pure O2 burns very slowly if at all"

I dont know about Carbon Monoxide, but I always believed that pure oxygen (O2) is highly flammable.  Its the life blood of an IC engine as IC engines basically burn air with the aid of a small amount of fuel (in comparison).

Anyway, further investigation needed.  Will post if and when I find anything else.

Mike

[iaint]

Originally posted by Mike

Was kinda following the chem bit, but got confused on...

"consider that pure CO and pure O2 burns very slowly if at all"

I dont know about Carbon Monoxide, but I always believed that pure oxygen (O2) is highly flammable.  Its the life blood of an IC engine as IC engines basically burn air with the aid of a small amount of fuel (in comparison).

From what I remember O2 doesn\'t burn (isn\'t flammable) in it\'s own right but is part of the reaction.  i.e. adding alot of O2 to normal combustion will ake the combustion faster (explosive in certain circumstances).

Under most circumstances adding O2 isn\'t safe or affordable but adding a component to the reaction that gives up it\'s O readily will increace the combustion.

I\'d guess that H2O is quite happy to give up the O part in the combustion process although this is counter-intuitive as H2O is very stable under normal temps and pressure and inhibits combustion.

Iain

[bill shurvinton]

Look at it another way. Complete combustion should end up with CO2 and H20. Of course it never works that way. Now reaction with oxygen is called \'oxidation\', its just that as we discovered fire before oxygen we prefer to call it burning. Same process though.

The early parts of the reaction, when things are very hot and at very high pressure tend to promote the reactions that produce CO. This CO needs to be oxidised/burned to make C02. Without WI the water produced in early combustion phases jumps in to help this. However this happens late on in the combustion, resulting in less power being delivered to the eccentric.

With WI you have excess water available near the beginning of the reaction which speeds things up, so that the energy released at a more beneficial time to transfer into the eccentric.

Bill

[Fish]

Here is a discussion that the US guys are having.

After a couple of pages two guys find they dont like each others point of view/idea\'s, but they settle down and it gets back on track.

I will also try and find the thread that is going on with the RX7Club forums.

Dan

[bill shurvinton]

What a funny forum nopistons is. That Dragon really ought to leak off some testosterone and pick up a textbook. If only people put their brains back into gear and thought rather than this chest beating \'you know shit because you only have 300HP\' rubbish.

Bill

[Carl]

Hi Bill and all,
I think that the reason that the water injection makes more power for less fuel is that as you lean out any engine it makes more power as the flame front is more efficient and not dampened down by excess fuel to prevent detonation.
Without the water injection the flame front is less stable in this leaner condition and so can move too quickly through the combustion chamber which can lead to detonation caused by the pressure build up from this front moving too fast towards pockets of unburned mixture and preigniting it.
 The water enables the flame front to be better controlled with leaner fuel ratios as it slows the combustion down and enables it to be controllable so that the flame front travels slower.The water absorbs some of the heat energy in the combustion.
Remember that lean makes more power than to rich but is more volatile. With water injection you can run leaner as you are no longer relying on the fuel to slow down the combustion process to control detonation.
Also the water has to expand in order to absorb the energy that is being produced by the leaner mixture of fuel and so in turn the water in a more controlled way is producing a rising rate of pressure in the combustion chamber which also drives the rotor or piston.
To sum up less fuel means more power with instability,water added to control the instability,water has in turn to expand and thus provides pressure in the combustion chamber which also makes  power.
I hope that this is a little easier to understand.
Kind regards
Carl:)