compression ratios

[mercutio]

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How It Works and FAQs
The main benefits of water injection are:
1. Will significantly help to prevent detonation.

2. Will raise the octane of the gas you are using.

3. By reducing detonation, this will allow you to increase boost or run lower octane.

4. Lowers air intake temperatures which keeps the engine cooler from the inside out.

5. Will literally steam clean the carbon deposits from within the engine.

What is Water Injection:

Water injection systems are predominantly useful in forced induction (turbocharged or supercharged), internal combustion engines. Only in extreme cases such as very high compression ratios, very low octane fuel or too much ignition advance can it benefit a normally aspirated engine. The system has been around for a long time since it was already used in some World War II aircraft engines, which allowed them to produce more power and therefore fly at higher altitudes.

A water injection system works similarly to a fuel injection system only it injects water instead of fuel. Water injection is not to be confused with water spraying on the intercooler's surface, water spraying is much less efficient and far less sophisticated.
A turbocharger essentially compresses the air going into the engine in order to force more air than would be possible with the atmospheric pressure. More air into the engine means automatically more fuel has to be injected in order to maintain the appropriate stoechiometric value of the air/fuel ratio (around 14:1). More air and fuel into the engine leads to more power. However by compressing the inlet air the turbocharger also heats it. Higher air temperatures lead to thinner air and therefore an altered stoechiometric ratio which can lead to a lean mixture and detonation. Detonation, an effect also known as engine knock or pinging, occurs when the air/fuel mixture ignites prematurely or burns incorrectly. In normal engine operation the flame front travels from the spark plug across the cylinder in a predefined pattern. Peak chamber pressure occurs at around 12 degrees after TDC and the piston is pushed down the bore.

In some cases and for reasons such as a poor mixture, too high engine or inlet temperatures, too low octane fuels, too much ignition advance, too much turbo boost, etc., the primary flame front initiated by the spark plug may be followed by a second flame front. The chamber pressure then rises too rapidly for piston movement to relieve it. The pressure and temperature become so great that all the mixture in the chamber explodes in an uncontrolled manner. If the force of that explosion is severe some of the engine's moving parts (pistons, rods, valves, crank) will be destroyed.
Detonation, in any engine, should always be avoided by either lowering inlet temperatures, using higher octane fuel, retarding ignition (hence lowering engine output), lowering engine blow-by (a situation in which high crankcase pressure sends oil fumes back inside the combustion chamber), running the engine a little richer than at the stoechiometric ratio, lowering the compression ratio and/or boost pressure, ... .
Water injection is used to lower in-cylinder temperatures and burn the air/fuel mixture more efficiently thus helping avoid detonation.

In high pressure turbocharged engines the air/fuel mixture that enters the cylinders can, in some cases, explode prematurely (before the spark plug ignites) due to the extreme engine environment conditions. This situation is extremely destructive and results in severe engine damage (piston piercing). To avoid damaging the engine by detonation or pre-ignition phenomena, water is injected, along with fuel, in the combustion chambers in order to provide a water/air/fuel mixture which not only burns more efficiently and avoids detonation or pre-ignition but also provides additional inlet air cooling and, hence, denser air. The sole functions of water injection is avoiding detonation by lowering air charge/cylinder temperatures along with increasing the effective octain of the air/fuel charge, so the ECU can advance timing and take advantage of the increased boost.

There are mainly three variations of water injection systems. They are dependent of the location of the water injectors. The first technique consists of injecting water at the entrance of the intake manifold. The second injects water at the exit pipe of the intercooler. The third technique injects water at the entry of the intercooler and is only used in competition vehicles. In this latter variation most of the in-cylinder detonation prevention is done by injecting additional fuel which is then used as coolant (i.e. is not burned) and runs the engine above the stoechiometric ratio (i.e. rich).

Frequently Asked Questions

Will water injection increase my horsepower?

Yes, but not directly. Water injection works to eliminate detonation, also known as knock. The big gains come from the ability to increase boost as well as the full ignition advance allowed by the ECU when it does not detect knock. While the cooling of the intake charge will produce some power increases, those increases are cancelled by the charge space occupied by the water vapor. In other words, there is slightly less room for air and fuel. However, by using up to 50 percent alcohol with the water, additional cooling takes place before the turbo, and the alcohol works as a fuel in the charge. This results in an increase in power.

Is water injection new?

No. Water injection was used during WWII to suppress detonation in fighter aircraft and increase their service ceiling.

What size injector do I need?

Every engine is unique, however the general formula is 1.0 - 2.0 gallons per hour (gph) per 100 horsepower. It is recommended to start on the lower end, and then increase from there if needed. Keep in mind when buying or building a two stage system that both injectors are running when at high boost, so your total flow is the rating of each injector added together.

Does the water "burn" in the engine?

No. The water simply converts from a vapor to a gaseous state which absorbs huge amounts of heat, due to the energy required to transform it.

What if my engine has an intercooler?

Most turbos do. Just install the nozzles right after the intercooler. We do not suggest injecting water before the turbo in an intercooled application, as most of the water will condense out at the intercooler. Also, alcohol and aluminum react when together.

Do I need an extra "tank" for the water?

Not necessarily. The systems are designed to use the original washer fluid tank (most have a built in level sensor), but you may choose to add a separate tank which you supply if you need something larger.

How often do I need to fill the tank?

It all depends on how often you use the system (it's only active under boost) and how big the tank is. Even the smallest tanks will last for 8 full 1/4 mile runs or so. In around town driving (agressive driving) a windshield washer tank that is a gallon in size should out last a tank of gas.

I have both of the hard pipes, the uppipe from the intercooler and the one from the airbox to the turbo. Where is the injector to be installed that would be the most efficient? Should it be installed in the pipe just before the turbo/throttle body or in the uppipe?

The injectors should most definitely be placed in the uppipe. If they are before the intercooler, it will eventually fill it with water, not allowing air to pass, or at the very least restricting it.

I have Stage 1, the AGP WGA, and I plan to install the diode to clamp the map sensor (conservatively). I don't plan on getting a boost controller at this time. Does this have any bearing on which kit that I should purchase? Which kit would you recommend?

No. However, the purpose of water injection is to keep the compressed air temperatures down, eliminating the need for the clamp. This way, your computer still has total control over the engine, just incase something fails.

Is a 100 psi pump enough? I see that the ones on Ebay are 140 psi.

The 100 psi pump is more than enough if you are running less than 20 PSI of boost. If you put out more than 20 PSI, then you must have the 150 PSI pump so the injector nozzles are pressurized enough for a completely atomized mist (pump pressure fights boost pressure). The 150 PSI pump produces an extremely fine mist. The more pressure the pump puts out, the finer, and more atomized the mist. The more atomized the mist, the more surface area a given amount of injected water has, and therefore getting better results.

Is the nozzle brass, high grade, and can it be installed on the outside of the pipe?

The nozzle is brass, definitely high grade, with a filter that is removable. As for mounting it, the other company sells this fancy sound nozzle set up, which I bought, and all it does is take up space in the uppipe, preventing airflow. The way I have them mounted now is just the injector head is on the inside of the pipe, which is only about the size of the tip of a Q-Tip.

Is there a high current relay switch?

Yes. There is a 30 amp relay switch. The relay and harness comes with all the kits, or is available separately for $7.99.

Is there an adjustable pressure switch for boost activation? Or is it pre-set for our Stage 1 boost levels if I don't have a boost controller and a boost gauge?

The pressure switch is adjustable from 1-25 psi. It takes a simple allen key to adjust the pressure, which is included with all of our kits. It comes preset to about 10 psi. The Vari-Cool Controller is adjustable with a start point as low as 1 psi, and a maximum point of as high as 30 psi.

Does the kit include the wire needed, and what gauge is the wire? Are there crimp terminals for wire hookups and a fuse assembly?

They will include red and black 14 gauge wire along with insulated crimping connectors and an inline fuse.

Any recommendations about the placement of the pump? Someone on the forums said that there would be one place under the hood where it could be mounted. Or do you prefer another location, and why?

Every car is different. On our car, we mounted the pump in the area available where the hood cowling meets the windshield. Another common place is inside the front bumber. The closer to the engine the better/easier/cheaper. If you need to/want to mount the pump in the trunk, there are no problems with this as the pumps are plenty strong enough to draw, and pump, any length that any car/truck could possibly have. The only difference with mounting the pump far from the engine is the extra wiring and tubing that will be required. Although not required, it is recommend to mount the pump lower than the tank, so if you do run the tank dry, priming is much quicker this way.

Is there a way to tell when the injection system is working?

There can be. All of the Stage 2 Kits have the clogged nozzle/flow detector switch. It is a pressure switch (solid brass and rated at 250 psi) that is placed between the solenoid and the injector. When the system activates and the injector is pressureized, the pressure switch will trigger and illuminate a small led light (included in all Stage 2 kits), which is usually mounted in a gauge pod. Also, when you let off the gas, the pressure should bleed off, therefore the light will go out. The light should go out immediately, but if the injector is clogged, the pressure will remain between the water solenoid and the injector, and the light will stay on, telling you there is a clogged injector. There is one detector per stage, so dual stage systems will have two.

[NafemanNathan]

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