Audi Man

I have not seen anything on water injection for rx7's. has anyone used it, and dose it work well on rotorys? I know that the rotoys are veary sinsitive to detonation and all, so i thought that it whould help out, anyone??

jspecracer7

Yes it's used on Rotary's. I myself run the Aquamist 1S.

ijneb

look in the archives- zerobanger has an excellent writeup.

Audi Man

cool, sorry did not know that there was archives tell now. thx anyhow.

Maestro

www.pinz.co.nz

Best W I System (Only one that tells you when you run out of water. Simple I know but 9 out of 10 systems don't)

Check out the site !!!

Audi Man

Cool system, but i have the aqua mist on mine, and i am kinda in love with the quality of it all. but i like the idea of it telling you when it is out.

ZeroBanger

whats water injection?

rotarypower101

iTrader: (1)

correct link

http://www.pinz-online.com/

sillbeer

by Julian Edgar


Water injection is a technology that is nearly as old as the car itself.
However, like many automotive technologies, it has waxed and waned as
fashion has dictated. Water injection has the ability to suppress
detonation, allowing the use of higher cylinder pressures. It is easy to
control and relatively simple to install. In times of tight emission
controls, decreasing fuel octane and rising petrol costs, water injection is
one of the best ways of controlling detonation. And it has another major
advantage over taking other approaches - the 'fuel' is available at almost
zero cost!

How it Works
Water injection is used to suppress detonation. Detonation occurs when the
flame front does not burn progressively across the combustion chamber but
instead explodes into action. This causes a massive and sharp increase in
combustion pressures which can damage pistons, rings and even heads.
Detonation can sometimes be heard as a 'tink, tink' sound coming from the
engine. The piston and head shown here has suffered severely from
detonation.

Water injection works in three ways. Firstly, when the water is injected
into the intake system prior to the cylinder head, the small droplets absorb
heat from the intake air. Water has a very high specific heat rating (it can
absorb lots of energy while only slowly increasing in temperature) and so
the intake air is initially cooled. Next, the small drops of water start to
evaporate. Water has a very high latent heat of evaporation (its change of
state absorbs a lot of heat) and so the intake air charge is cooled still
further. Finally, when the remaining water droplets and water vapour reach
the combustion chamber, steam is produced. This acts as an anti-detonant and
also keeps the interior of the engine very clean, so preventing the build-up
of carbon "hot spots".

Water injection was first experimented with in the 1930s. At the time it was
discovered that detonation could initially be prevented by enriching the
air/fuel ratio. As cylinder pressures rose still further and that approach
ceased being effective, the injection of water into the intake air stream
was found to prevent detonation. Interestingly, the detonation remained
suppressed, even if the air/fuel ratio was then leaned-out. This occurred
because the excess fuel was being used to cool the combustion process. When
water replaced fuel in performing this function, less fuel was then
required.

This has major implications for both emissions and fuel economy at high
engine loads. In fact Saab on some of their recent turbocharged cars has
used water injection at high loads in conjunction with leaner air/fuel
ratios to reduce emissions output and improve fuel consumption. To put this
another way, at high engine loads it is possible to reduce the amount of
fuel being used, replacing it with water without sustaining any loss of
power!

Always Water?
While I have referred to 'water' injection, many systems add a 50/50 mix of
water and methanol, or water and methylated spirits. Research carried out
during World War II indicated that pure water is best at suppressing
detonation, while a 50/50 mixture of water and methanol permits the greatest
power output before detonation occurs. One reason for this may be that the
alcohol burns more slowly than petrol, so causing peak cylinder pressures to
occur at a later crankshaft rotation, increasing torque.

The question of whether a water injection system can increase engine power
is a contentious one. While the intake air will be lower in temperature (and
so denser) when a water injection system is operating, the presence of an
increased amount of water vapour in the air means that there is less room
for oxygen. It is for this reason that dry air (that is, air with a low
relative humidity) can allow an engine to develop more power. So when the
air is cooler but its water vapour content is higher, will more power be
developed? If no changes are made to air/fuel mixtures, theoretically the
two factors almost exactly cancel each other out.

This means that if water injection is used without any changes made to the
tuning of the engine, improvements in power are possible but not probable.
However, if the engine air/fuel ratio is leaned out, or boost is increased,
or the ignition timing is advanced, more power is very likely. Supercharged
aircraft engines using water injection had mechanisms that leaned out the
air/fuel ratio simultaneously with the operation of the water injection.
However it is very important to note that making random changes to the
air/fuel ratio and ignition timing at high engine loads can be very
dangerous for the health of the engine. Such changes should be made with
care - it is very easy to blow up a forced induction engine with random
leaning of the mixtures and/or ignition timing changes!

Both methanol and methylated spirits mix well with water when it is required
that a mix be injected. However it is important to note that both of these
mixtures are inflammable and so the anti-detonant injection system's storage
container, pump and lines should all be designed and installed with the
carriage of an inflammable liquid in mind.

Note that it has been suggested in some circles that the water can be
directly added to the petrol by using a solvent such as acetone. However, I
have not heard of anyone actually doing this!

Water Injection Systems
A water injection system should:


Distribute the water equally to each cylinder;


automatically start the water flow prior to it being required;


have positive shut-off (eg via a solenoid valve) when water injection is not
required;


either warn the driver or decrease engine power (eg by dropping boost)
should the water supply be exhausted;


be very reliable.

Many aftermarket water injection systems do not satisfy any (let alone all!)
of these criteria.

To be most effective, a water injection system should add water in
proportion to the changing airflow. In other words, the flow of water should
match the flow of air, with small amounts of water being added at low loads
and high amounts at high loads. If very accurate control of the water
injection quantity is available, maximum water flow per cfm of induction air
should occur at peak torque when cylinder pressures are at their highest.

The water should be injected in as fine a spray as possible. Doing this
results in each drop being smaller, increasing the surface area to volume
ratio and so promoting evaporation. The smaller drops are also less inclined
to fall out of the air, wetting the intake manifold walls and perhaps then
being distributed unevenly from cylinder to cylinder. A small droplet size
means that a high-pressure pump and a well-designed spray nozzle are
required.

UK company URL at www.aquamist.co.uk produces some very sophisticated water
injection systems - probably the world's best. The company has developed
their own pumps which work at high pressures and low flows. The pumps use an
approach a little like a bicycle pump. Water is drawn in during the
induction stroke of the solenoid-like pump, then pushed out past a valve by
internal spring pressure. The stainless steel armature pulses in this way 50
times a second, delivering up to 160cc a minute at over 70 psi. The pump has
built-in electronics to control this pulsing, with a 0-12 volt input control
signal able to vary the flow. While URL use a sophisticated ECU to control
some versions of the system, the availability of the control signal input
means that the output of the airflow meter or MAP sensor could probably be
adapted for the same purpose.

An alternative to a pump is to use boost pressure to force the water through
a nozzle. If this system is adopted, the spray can be used only in a forced
induction car with the water introduced prior to the compressor. A very
special nozzle is also needed if the spray is to be sufficiently fine to
pass through the compressor without long-term damage occurring. People using
coarse droplet water injection in front of turbos have reported that over a
period of time the edge of the compressor blades develop a serrated edge -
presumably from the impact of the water droplets.

The injection of water can occur at a number of different points within the
intake system. In a naturally aspirated car, the nozzle is usually situated
prior to the throttle body. In a forced induction car, the nozzle can be
situated:


before the compressor,


after the compressor


after the compressor but before an intercooler


after an intercooler.

URL suggest a nozzle position just prior to the throttle body for road cars,
while the supercharged aircraft of many years ago used up to 18 nozzles
positioned around the supercharger exit diffuser. Testing of the two systems
discussed below indicated that the best nozzle location should be found
through experimentation. The amount of water that needs to be added to an
engine is also best assessed through trial and error. If the flow of water
is initially high and then is slowly reduced, this approach can be done
quite safely. However, testing on aircraft engines indicates that the mass
of water required to suppress detonation is 20-30 per cent of the weight of
the total liquid charge (that is, the water plus the petrol) being consumed.
The system should be configured so that water is only ever injected when
there are high intake airflows.

Boost Pressure Water Injection
A good quality boost-pressure controlled water injection system can be built
using off-the-shelf components. The system gives an extremely fine spray and
can be used with water/methanol as well as pure water. While the injection
of water is not proportional to load (it is proportional to boost pressure),
there is a variation in the supply of water which is still better than many
systems provide. The best part of the system is that it is maintenance-free,
other than requiring the refilling of the water tank as required and the
occasional cleaning of the filter.

The nozzle used is an air atomising design produced by US company Spraying
Systems. It has two connections - one for compressed air and the other for
water. The compressed air is directed out of two orifices so that it
collides with the water stream, scattering it into the tiny droplets. The
pressure to supply both the water and the compressed air comes from the
turbo or supercharger. The part number for the nozzle is SUE18A and it is
available from agricultural irrigation and spray suppliers.

Unlike many air atomising nozzles, the SUE18A works effectively at pressures
below 50kPa (7psi). Around 200 ml/min flows through the nozzle when it is
supplied with water and air at around 20 psi (1.4 Bar) boost. If this flow
is too great, a ball valve can be placed in the water supply hose to allow
easy adjustment of the flow. If the ball valve is closed down to restrict
the water supplied, the remaining water will then be even better atomised!
If more than 200 ml/minute of water is required I suggest that you use two
or more nozzles.

The water supply for the nozzle should be through a small water filter to
avoid filter blockages occurring. An appropriate filter is available from
the suppliers of the nozzle or a small garden irrigation filter can be used.
The nozzle must be mounted so that it flows into the intake system before
the compressor and the water should be injected after the airflow meter (if
present) to prevent the water droplets upsetting the air metering.

The fluid storage container must be pressurised if the water is to be forced
through the nozzle. A custom tank can be made or a large pressurised
radiator header tank pressed into service. Preferably the tank should be at
least 5 litres in volume for each nozzle used. Note that the tank must be
capable of handling the constant cycling of internal pressures up to the
peak boost level. A low fluid warning buzzer should be fitted.

Plumb the system using a ball valve to adjust the supply of water and a
boost-pressure triggered solenoid (pictured) to give a positive starting and
stopping behaviour. An alternative to the use of the solenoid is to install
a vacuum-operated valve (such as the EGR valve) to vent the tank back to the
inlet system, causing the tank pressure to more closely follow boost when
the throttle is lifted. However, the solenoid valve is the safer of the two
approaches: if the water ever flows into the intake when the engine is
stopped, very major engine damage can be caused when it is attempted to be
re-started!

Pumped Water Injection
If you require that the water be injected after the turbo or supercharger,
or a large pressurised tank is unwieldy, a pumped system is a better option.
This type of system is also suitable for a naturally aspirated car.

The pumped water injection system again uses Spraying Systems nozzles. The
SF2 and SF3 Fogging Nozzles are designed for humidifying the air in chook
sheds, amongst other agricultural applications! The nozzles require only
pressurised water to produce a fine spray, although note that the droplets
are not as fine as those produced by the air atomising nozzle described
above. The nozzles can be equipped with in-built filters and check valves
that prevent them dripping.

The electric pumps used in for agricultural crop spraying or in good quality
windscreen washer systems can be used. If the spray nozzle is located after
the throttle butterfly, a solenoid valve should be inserted in the water
supply line so that there is no possibility of water being sucked through
the pump during periods of high manifold vacuum. The easiest activation
technique for the pump is to use a manifold pressure switch that simply
turns on the water injection when the engine is on boost, though of course
this then does not give proportional control. Another approach that will
give slightly earlier switch-on is to use a throttle microswitch (pictured).

Another entirely different way of varying the water injection rate is to
drive the pump with a trailer electric brake controller. These devices are
available from caravan and similar suppliers and are designed to energise
the electro-magnets that are located in the brake assemblies of some
caravans and trailers. One class of controllers does this by measuring the
braking force that the car is undergoing and increasing its output voltage
proportionally. I envisage the controller reversed in orientation so that it
measures acceleration. If it was then connected to the water injection pump,
the harder the car accelerated, the higher would be the pump speed and so
the greater would be the addition of water into the intake air!

Water Injection versus Intercooling
So which is better if you are running a forced aspirated car - water
injection or intercooling? Each has its own advantages and disadvantages.
Intercooling is a reliable means of reducing intake air temperatures and
depending on the approach chosen, it can be a very simple system. However,
it should be noted that while air/air intercoolers have few component parts,
water/air intercooling is more complex than water injection. Intercooling
systems require little or no maintenance, and a good intercooling system
will provide an engine power increase in addition to preventing detonation.
However, intercoolers are much larger than water injection systems and are
generally harder to package. Finally, all intercoolers cause a restriction
to intake flow.

Water injection is very effective at preventing detonation. It is not
subject to efficiency drop-offs through heat soak and causes no restriction
to intake flow. It is easy to fit as an add-on to an existing system, and
because its components can be spread around the car, it is generally very
easy to package. Unlike intercooling, water injection will not necessarily
give a power increase. However, the biggest disadvantage is the requirement
to carry a relatively large water tank - and to keep on filling it!


Advantages

Intercooling
Reliable
System can be very simple
Always improves power
System break-down usually immediately recognisable
No ongoing maintenance

Disadvantages

Weight
Bulk
Major underbonnet changes
Usually poses a flow restriction

Advantages
Water Injection
Very effective at preventing detonation
System components can be spread around car
Can be used to inject octane booster
Generally low cost
No intake flow restriction
Reduces emissions


Disadvantages
Requires regular filling of water tank
System breakdown can be difficult to recognise
Large filled water tank is heavy
Variable flow systems are complex
Effectiveness will vary depending on weather

911GT2

He was kidding sillbeer. He (Zero) was the one who wrote up the how to based on his own WI system for his car.

radkins

Holy **** thats the longest post I have seen on the forum.

ZeroBanger

I gots to learn how to use the smiley thingy, huh?