ERL Aquamist Water Injection SystemsThe Aquamist HFS3 Water Injection System
The concept of injecting water into the internal combustion engine has been around for over 50 years.
But the desire to extract more power from the standard production engine has increased at a neck-breaking speed.
Aquamist has revived this old principle, and applied the latest techniques in both electronic and mechanical engineering to take water injection into the next millennium.Aquamist's website reads ... "to be more precise: 7,124 of these water jets have been sold. Ford motorsport was responsible for consuming over 5,000 of them."
Who uses water injection ?
Water injection has been seen on everything from Ferrari Formula One cars, Renault Formula One cars, circuit racing cars, a wide range of World Rally Championship cars and modified street cars.
Click here to view a range of racecars, rally cars and street cars running water injection systems:
- Renault Formula One water injection info
- World Rally Championship Toyota
- World Rally Championship Ford
- World Rally Championship Hyundai
- Rally Saab water injection info
- Road cars water injection info
Why water injection ?
When we apply heat energy to water and it turns into a gas, a great deal of heat is absorbed during this process.
This is due to water's specific heat capacity - approximately 4.2kJ/(kg.K).
When the water changes from the liquid to gas state, a large amount of heat energy is consumed in sustaining the process. The latent heat of evaporation is 2256kJ/kg, approximately six times more than gasoline.
Because of its huge specific and latent heat capacity, water is the perfect liquid for regulating excess heat under certain engine-operating conditions, for example induction charge air cooling.
But water's biggest contribution is inside the combustion chamber where, under excessive loading, pre-ignition and detonation can otherwise occur. Such abnormal combustion is particularly common in force induction engines, where exhaust temperature can exceed 1100°C.
What chance has a piston got under these conditions, given that aluminium melts at 660°C?
The dangers of fuel dumping
Some people tuning their cars keep exhaust temperature below 850°C by fuel-dumping (dumping extra fuel into the engine to lower the combustion chamber temperatures).
And hold crown temperature below 550°C (by conduction to the underside and skirt of the piston, which is constantly being quenched by engine oil).
But the hidden drawback of using excess fuel / an overly rich air fuel ratio to try to manage combustion and exhaust temperatures is that even more fuel is being dumped -- as a coolant.
As you richen your air / fuel ratio by adding more fuel to try to address the combustion chamber temperature issues, you will get to the point where the air / fuel mixture becomes so rich, and the flame is burning so slowly, that power is being lost rather than gained.
Worse still, your piston is no longer being lubricated properly because the excess fuel can wash down the piston wall (bore-wash) and eventually contaminate your engine oil with fuel, which prevents your engine oil doing it's job properly.
We saw a car a few years back which had been incorrectly tuned with an overly rich air fuel ratio - the result was the premature failure of two very expensive engines with bottom end bearing failure.
The Aquamist solution
The Aquamist system, using sophisticated electronics to process engine data, injects a precisely-metered quantity of freely available water into your engine's intake tract.
Aquamist eliminates the need for fuel-dumping:
- leaving your air/fuel ratio unaffected
- enabling maximum power to be extracted from the engine.
To ensure that each cylinder receives exactly the same dosage, the Aquamist system delivers the water in a fine mist.
How water injection increases the knock limit of the engine
Knock primarily occurs under wide-open-throttle (WOT) operating conditions. It is thus a direct constraint on engine performance. It also constraint engine efficiency, since by effectively limiting the temperature and pressure of the end-gas, it limits the engine compression ratio or boost pressure on a forced induction engine.
Apart from using higher octane fuel or additives such as alcohols, lead alkyls, another factor affecting the engine's tendency to knock relies upon the ability of the engine designer to achieve the normal combustion behavior while holding the engine's propensity to knock at a minimum.Cylinder pressure versus crank angle diagram - click to enlarge
The figure above shows cylinder pressure versus crank angle traces of cycles of different operating conditions. As suggested the above figure indicated four consecutive plots of cylinder pressure against crank-angle, ignition timing is three degrees apart between each trace.
As seen on the figure, the green trace represents the normal combustion cycle.
If the ignition is advanced by some three degrees, a slight knock occurs on the yellow trace, indicates the engine has reached its limit.
Further timing increase produced severe knock (red trace), this level of knock is audible to the human ear, it should be prevented from happening for prolonged periods, as permanent engine damage can occur shortly afterwards.
The blue trace is placed approximately between the red trace and the yellow trace, ignition timing is around 6 degrees advanced of the normal green trace, but this time water is being injected into the engine.
Before TDC, the blue trace followed a predictable path except soon after the TDC, the pressure begins to flatten.
As the water within the combustion chamber started to evaporate and absorbed a large amount of the heat and prevented the pressure and temperature reaching the point of detonation. The trace now follows the green trace until the next cycle.
Note the area under the blue trace is much larger than the green trace indicating torque increase. More gains are to be expected on the turbocharged engine.
The Tuners Group is a dealer for Aquamist systems.
We can supply two system from Aquamist, the Aquamist HFS-3 Water Injection System, and the top of the range Aquamist HFS-6 Water Injection System.
Please click on the links below for info on each system: