There are plenty of write ups that go into detail about the pros and cons of alky/meth/water injection, but none that explain how to choose a kit... so I thought I'd take a stab at it. I wrote this before Richard of Aquamist wrote his In-depth study of WAI injection systems (http://forums.nasioc.com/forums/showthread.php?t=1413320), so naturally it will overlap and go much more in-depth in some areas than I will. For further reading, please refer to that thread. My goal here is to provide you with a basic, unbiased understanding of how these kits work, what the major differences are, and what each manufacturer has to offer. Fyi, I’ll be using the word “water” here interchangeably with meth, alky, or whatever you plan on injecting. Please feel free to let me know (gently) if I've made a mistake.

STEP 1: single vs. dual stage.
1. Single stage (on/off): using a boost switch,
http://www.coolingmist.com/instructions/09largeimage3.jpg
these kinds of kits simply come on at a certain manifold pressure, and spray at a set flow rate until pressure drops below a certain psi. If you have your kit set up to spray 5 gph at 15 psi, you’ll spray 5 gph at 15 psi and above, and not spray at all below 15 psi.
Cons: water delivery will not adapt to changes below or above the preset pressure. It will not provide you with the knock prevention you’ll need at anything below the pressure you’ve set, and will not provide increased knock prevention as rpm and pressure rise passed the set pressure. The effects of this varies with different setups (further explained in "MAP based controller").

Single stage kits:
Coolingmist (http://coolingmist.com/pagedisplay.aspx?feature_key=standard)
Aquamist System 1s (http://www.aquamist.co.uk/cp/sys1/sys1a.html)
Aquamist HFS-1 (http://forums.nasioc.com/forums/showthread.php?t=1223950)
Devil's Own (http://www.alcohol-injection.com/water-injection-kits-1/universal-19/base-alcohol-injection-8.html)
Snow Performance (http://www.snowperformance.net/product.php?pk=6)

2. Dual (progressive): these kinds of kits have variable flow rates, increasing and decreasing flow in accordance with your car's activity. These kits have controllers that vary flow in different ways, which I will explain in the following section.
MAP based progressive controller: These kits determine when to inject water based on manifold pressure (just like single stage). The difference is flow rate is not static; it rises and drops in accordance with manifold pressure. The start and end points can be adjusted by the user.
SMC’s MAP-based controller:http://i138.photobucket.com/albums/q247/WReXd/smccontroller.jpg
Cons: Flow should increase and decrease based on the volume of air ingested. Unfortunately, pressure is not always a good indicator of that. The volume of air at a given pressure increases with rpm, which pressure does not account for. If you hit your max pressure set at 20 psi and it tapers to 16 at 7k rpm (which is typical), you’ll be spraying LESS water when you actually need MORE. Ideally, your engine should be combust twice the amount of air at double a given rpm. Fortunately, this is not always the case due to a decrease in volumetric efficiency. Smc, devil's own, snow performance and coolingmist all have MAP based kits.
FIDC-based controller: Fuel injector duty cycle is arguably a better way to determine flow, since it rises and falls in accordance with total volume of air ingested. This solves the MAP problem I mentioned earlier. Labonte MotorSports, Aquamist, and Perrin (whose kit is made by Aquamist) make fidc based kits. They monitor IDC and determine how much water to inject based on that. Labonte's is actually 2d (see below).
Here’s a pic of Aquamist’s:http://www.aquamist.co.uk/cp/806-009/amp.JPG
MAF-based controller: Since the ecu determines how much fuel to inject based on the MAF sensor, MAF-based controllers also have the same advantages as FIDC. Fortunately, Subaru's MAF sensor works just like the MAP (varying 0-5v analog signal), so some MAP-based controllers will work with the MAF sensor.
2d Mappable Controller: Some progressive controllers can determine how much to inject based on multiple (2 or more) inputs. Aquamist's MF2 (http://www.aquamist.co.uk/cp/mf2/mf2.html), Coolingmist's Smart Injection (http://coolingmist.com/detailmain.aspx?pid=1099), and Labonte MotorSport's VC3G (http://www.labontemotorsports.com/store/ccp0-prodshow/VCS3G.html), Fjo's CWI0010 (http://www.fjoracing.com/products/waterinjection/parts.php) all have the ability to inject based on 2 or more variables. Any controller that includes on of these controllers will be able to inject based on multiple inputs.

There are additional possibilities depending on what other hardware/software you have, but these are the most common.

Dual stage kits: (For Aquamist and Fjo, scroll down)
AEM (http://www.gruppe-s.com/Subaru/subeng.htm)
Coolingmist (http://coolingmist.com/pagedisplay.aspx?feature_key=controllerkits)
Devil's Own (http://www.alcohol-injection.com/water-injection-kits-1/universal-19/progressive-alcohol-injection-12.html)
SMC (http://www.smcenterprises.com/subaru.htm)
Snow Performance (http://www.snowperformance.net/product.php?pk=8)
Labonte MotorSports (http://www.labontemotorsports.com/store/ccp0-prodshow/ISG-10.html) (Controllers (http://www.labontemotorsports.com/store/ccp0-catshow/InjectionControllers.html) sold seperately)

STEP 2: failsafes
You need to find a good way to prevent damage in case of an emergency (aka your kit fails). Engine management can help, but only to a certain extent (again, I won't go into detail). It’s highly recommended that you buy a kit with a good failsafe, or buy one separately. The reason is simple; if your meth kit fails and you're not adequately prepared... BOOM! There goes your engine! Imo, the failsafe is THE most important thing about a WI kit.
Coolingmist's smart injection:http://coolingmist.com/products/images/1099large.jpg
How a failsafe works:
A failsafe is a device that monitors an engine's and/or WI kit's activity through the interpretation of one or more inputs. Using these inputs, the failsafe device will determine whether or not the WI kit is working properly. Common inputs include flow sensors (offered by Aquamist, Labonte) and clog detectors (coolingmist). Upon sensing a fault, the failsafe will activate one or more outputs, which stop the engine from running under aggressive settings.
The most common approach various companies have taken is boost cut. They use some sort of device to monitor flow, so if the line gets clogged or the tank empties, power to the boost control solenoid is cut, reducing boost to wastegate pressure (which is ~7psi stock). There are other methods, but I’ll be here all day if I go into too much detail. Instead, here are some links. Fyi, smart injection is my favorite, with the DDS3 following in second place.

Smart Injection (http://www.coolingmist.net/instructions/smartinjection.pdf)
Aquamist DDS3v8 (http://www.aquamist.co.uk/press/DDS3-v8-web.pdf)
AEM kit w/ failsafe (http://www.gruppe-s.com/Subaru/subeng.htm)
Snow Performance Safe Injection (http://www.snowperformance.net/product.php?pk=13)
Labonte MotorSports IFS-10 (http://www.labontemotorsports.com/store/ccp0-prodshow/VC-IFS-10.html)

STEP 3: flow precision/dynamic range
If you plan to go progressive, you'll have to consider how well the kit will respond to varying flow demands. Most progressive kits alter the speed of a pump's motor to vary pressure and flow. There are 4 main concerns with this method:
1. Speed: Many are doubtful of the common shurflo pumps' ability to respond to the fast-changing demands of WI kits (pic below).
http://www.snowperformance.net/product_images/product-large_image-38.jpg
The concern is that the shurflo's rotating internals generate too much inertia to be able to respond quickly enough to drastic changes, as demonstrated here (http://forums.nasioc.com/forums/showthread.php?t=1199190).
2. Dynamic range: unfortunately, flow and pressure do not increase at the same rate. This means a drastic increase in pressure will only result in a minor increase in flow.
3. Atomization: a decrease in pump speed results in a decrease of pressure, which results in poorer atomization. Small droplets are needed to ensure the vaporization of all water injected.
4. Longevity: obviously, a pump whose motor speed is continually increasing and decreasing will not last as long as one that is used at a consistent rate.
There are two ways companies have tried to remedy these problems: the high speed valve,
http://www.coolingmist.com/products/images/S-HSVlarge.jpg
and the electromagnetic piston (aka race) pump.
http://www.turbobits.co.uk/acatalog/erl_aquamist_2001grey_320.jpg Because of the speed and precision of their lightweight moving parts (which are kept to a minimum), both the hsv and the race pump can dramatically increase or decrease flow within moments. They also operate at full pressure 24/7, so atomization is not an issue. Here are some examples of kits with HSVs and race pumps:

Coolingmist (HSV):
Coolingmist S-HSV kits (http://coolingmist.com/pagedisplay.aspx?feature_key=s_hsv_kits)
EDIT: Coolingmist's valve is quite different from other hsv's and injectors. It is a proportional valve, which works like a variable restrictor instead of a simple on-off solenoid valve (like Aquamist's and FJO's).
Aquamist (HSV):
System 2c (http://www.aquamist.co.uk/cp/sys2c/sys2c.html)
System 2d (http://www.aquamist.co.uk/cp/806-009/806-009.html)
System 2 (http://www.aquamist.co.uk/cp/sys2/sys2a.html)
HFS-5 (http://forums.nasioc.com/forums/showthread.php?t=1183963)
Perrin (Race pump):
PWI-1 (http://www.perrinperformance.com/products/show/287)
Fjo Racing (HSV):
Water Injection System (http://www.fjoracing.com/products/waterinjection/)

To conclude, there really is no “best kit for the money.” If you spend less, you’ll get less. That’s even true (to a certain extent) between different brands. It may seem like I favor Aquamist and Coolingmist (which I do), but their "premium" kits are almost double the price of everyone else’s. You can get another kit that is stupid simple, costs much less, and get 80% of the benefits. You could even build your own if you want (which is actually what I’m doing). However, alky/meth/water injection is no joke. If you don’t do things right the first time, you might not get a second chance. This isn’t the typical “plug and play” mod for your typical suby folk. Yeah, it’s a great power-adder, but proceed with a plan, proceed with caution, and above all, proceed with knowledge. If anyone has questions, feel free to reply to this post or pm me.

Thanks for taking the time to put this together, I think its a great idea and definitely should be a sticky...

Its a good start but I don't think its quite yet "sticky" worthy. How about some common examples of brand name "on/off" kits and progressive controller kits, as well as their retain prices? I know AEM released a kit that is very affordable, but how's it compare to brand x, y, or z? Just do a quick comparison chart of the common kits: SMC, Aquamist, Coolingmist, Snow, DevilsOwn, etc..

An explanation of a true failsafe is necessary for people just learning about meth kits. Showing a picture of coolingmists smart injection and clog nozzle detector might confuse a noob into thinking that a CND is a failsafe. When its not.

yes - your write ups really help out.

Thanks for the compliments and suggestions, guys. I will take them into consideration and continue to edit the original post.

Its a good start but I don't think its quite yet "sticky" worthy. How about some common examples of brand name "on/off" kits and progressive controller kits, as well as their retain prices? I know AEM released a kit that is very affordable, but how's it compare to brand x, y, or z? Just do a quick comparison chart of the common kits: SMC, Aquamist, Coolingmist, Snow, DevilsOwn, etc..

An explanation of a true failsafe is necessary for people just learning about meth kits. Showing a picture of coolingmists smart injection and clog nozzle detector might confuse a noob into thinking that a CND is a failsafe. When its not.

It is actually part of a failsafe. Smart Injection was designed to be as simple or as complex as the customer wants/needs. Smart Injection can be user defined, this is one thing that seperates this failsafe from others. When mated with the Smart Injection the CND (Status Monitor) can do the following:

Detect a clog
Detect a harware failure
Detect a nozzle that popped off
Flowing when it should not be
Not flowing when it should be.

The status monitor will at all times indicate line pressure to the smart injection, the smart injection knows if your system should or should not have pressure at the nozzles and can based on that provide decision support for failsafe activation.

The status monitor option gives someone an economical way to provide 95% of what a flow sensor will at a fraction of the cost.

We do have a flow sensor option that will be available shortly for it, also those that have a flow sensor from a different company can integrate it into the smart injection unit as well.

Just wanted to clarify when mated with Smart Injection, the CND (status monitor) does perform failsafe functions quite well.

CM

Thats some good info.

Just wanted to clarify when mated with Smart Injection, the CND (status monitor) does perform failsafe functions quite well.

CM

I agree 100% with Coolingmist. I just wanted clarification in the sticky of what a true failsafe is. Obviously the CND alone, is just a status indicator. It isn't a failsafe until mated with a monitor that will cut boost.

Agreed. There are different levels of "Failsafe" available.

At bear minimum a failsafe needs to have the ability to perform atleast one action (activation/deactivation) based on atleast 1 input. Just an LED or Just a gauge is just a visual indicator.

What we wanted to do with Smart Injection was give the customer unlimited customization. 7 inputs, 1 programmable 0-5V output, 1 5V output and 5 on/off channels and 3 visual leds that can all be activated/deactivated based on as many or as little conditions as you can think of. While failsafe must be setup with your computer, it has far better potential than the others on the market as you can customize it.

Post updated. Comments and suggestions are welcome.

how can we connect the fail safe (smart injection) to cut boost then?

Smart injection has 5 ground activation outputs as well as a programmable 0-5V and of course 7 inputs.

You have many, many ways to do what you are seeking. For example, our smart injection failsafe has an optional status monitor that can detect a problem in the line. If it detects a fault, one of the outputs can activate a wastegate solenoid. Thats option #1. Option #2 which may work for some of you...If you have an aftermarket electronic boost controller..use one of the smart injection outputs as the ground to your electronic boost controller. Any problems in the line, hardware, out of water, de-activate the ground. This SHOULD disable the boost controller and bring you back to wastegate pressure. Again, you will need to make sure your boost controller works in that fashion, if not you can do option #1.

CM.

Snow Performance offers a non-progressive injection system. It is our most basic, entry level system and is recommended for low boost or WOT applications.

We also offer injection systems that read Mass Air Flow ouput. MAF referencing is typically the most accurate way to manage injection for applications that build boost quickly. This is usually the case with small, quick spooling turbos or positive displacement superchargers. A majority of the Subaru vehicles will use a MAF referenced system so I suggest making this a part of your guide.

Nate

thanks for the input. I will edit my post.

WReXd:

Labonte MotorSports now offers a complete line of Injection Controllers, Injection Kit, Fail Safe, Flow Gauges and more. Our new VCS3G controller is an advance fueling computer for water methanol injection. Also - we have been manufacturing the Injection contollers that Snow sells since 2002.

Best regards,

Dan

Yeah, you guys just popped out of nowhere when I started writing this, so I didn't get a chance to include your products. I questioned your credibility at first since I didn't know much about you guys, but I do now, so I'll edit my post.

Thanks WReXd,

Just some FYI on our products:
Our MAP based controllers (VC-25, VC-100, VC-25D) all have an internal MAP sensor. The VC-MAF is of course for connecting to Mass Air Flow sensors. Our VC-A10 is for Naturally Aspirated Engines, Internal Vacuum sensor and programmable RPM switch for activation.

The VCS3G does not just mirror FIDC. It actually uses IDC to calculate fueling into the engine and then uses Boost to determine to correct amount of fluid to inject.

It was our VC-25 controller back in 2002 that first came out with the Start and Full dial adjustments based on boost pressure.

We also have the ISG-10 which is an universal injection kit (pump, tank, hose, nozzles etc) similar to what everyone else has.

Otherwise good summary on what is on the market. I would like to see a shoot-out done by a third party that compares performance of various systems/controls on a standardized vehicle. I would donate some parts for such an effort.

Best regards,

Dan

Our MAP based controllers (VC-25, VC-100, VC-25D) all have an internal MAP sensor. The VC-MAF is of course for connecting to Mass Air Flow sensors.

Do your MAP controllers have mechanical (rubber line) or electrical (0-5v) inputs? Also, what kind of input does your MAF controller need? They don't always work the same way. On our cars it's a 0-5v signal.

The VCS3G does not just mirror FIDC. It actually uses IDC to calculate fueling into the engine and then uses Boost to determine to correct amount of fluid to inject.

Sorry about that. I first wrote this before I knew about your controller, so Aquamist was the only manufacturer I knew of that used idc.

Otherwise good summary on what is on the market. I would like to see a shoot-out done by a third party that compares performance of various systems/controls on a standardized vehicle. I would donate some parts for such an effort.

I would love to host a test like that, but I don't think I'd have the necessary time, resources and knowledge. Now, if other locals were willing to help out, and you sent me a complimentary gift (hint hint... VCS3G) that might change things.

All our controllers with MAP input have an internal sensor. There is a hose barb fitting on the back of the controller to connect a rubber hose from a boost pressure soruce (Or vacuum source in the case of the VC-A10)

The VC-MAF can work with 0-5v hot wire MAF type sensors or karman vortex frequncy based MAF sensors. There is a 3 position switch on the controller that lets the user select the type of MAF sensor.

Best regards,

Dan

I would like to update ours. Our smart injection now offers 2D grid mapping programmable output. You can use any 2 inputs (air temp, rpm, map, maf, egt, tps, etc) and enter the dutycycle in the cell for exact programming. This will make injection very precise.

http://www.coolingmist.net/images/rpmmap.jpg

YAY! I've been waiting for this!

http://www.coolingmist.net/images/rpmmap.jpg

FYI, I have been doing research in making my own water injection kit. I have heard that WWII aircraft had water injection, and the setup was a progressive system

The components are:

Sealed reservoir tank
Hose from pressure side of intake system to tank (after turbo)
Hose from tank to low pressure side of intake system (before turbo)
Spray nozzle on low pressure side of intake system
Bleed valve for tankAs boost pressure rises, the pressure in the tank rises, forcing water out through the injector. Adjust the bleed valve to change the boost level at which the nozzle starts spraying water. Adjust the nozzle sizes to control the amount of water injection. More boost equals more water injection when you need it.

I have not tried this system myself yet, but plan to within the next month or two. Thoughts?

Brian

Search on the internet for the Mr. Freeze system. What you discribe is how it works.

Best regards,

Dan

Sho' nuf. Thanks for the tip.

http://www.andersonfordmotorsport.com/mr-freeze.html

Thanks! This is a HUGE help!

is there a system i could turn off from within the car? with the new Si drive, i could say run WI in 1 mode and a non WI map in another mode. if a problem arrived, turn the system off from within the car and changes maps wi the Si drive. this is basically what i am looking for in a WI system.

thanx, mike

Any of our kits that have our Smart Injection unit have the ability to turn on/off any device including a water injection kit. To switch MAPS if that is simply sending a 12V, Ground or 0-5V, our system can do that. We have 5 outputs that can be used for things like this.

You forgot one big player in the meth injection scene that has a great standalone and utilizes a HSV: FJO Racing www.fjoracing.com

I apologize, I don't think I've heard of Fjo before. Looks like they have some pretty cool stuff. Their controller can do a lot, and their HSV is affordable. Original post is updated, with a question for Coolingmist (Look for red font).

EDIT: I'm not sure Coolingmist's hsv works the way I thought. After doing some reading, it seems to me like their valve may be a proportional valve (works sort of like a variable restrictor) instead of a high-speed on/off valve. Maybe Coolingmist will chime in.

You can run this valve several different ways, its easily one of the most flexible valves on the market.

Option #1 is you can PWM the valve with a fixed frequency, increased current=increased flow. You can think of this as dutycycle based. This is identical to they way most progressive controllers PWM a pump except the valve is much faster, hence high speed. The term high speed refers to the fact that it can change the flow rate, very, very fast with low hysterisis.


You can use a 0-5V. Your 0-5V signal MUST be able to produce 5 Watts at 5V. This can work using NO frequency at all. No PWM signal. 5 volts means it opens all the way, 0 volts=closed, the orifice opening will be relational to the voltage. This is a very fast way to work the valve and the valve will not buzz like a bumble bee. If your circuit cannot handle 5 W at 5 volts you need a driver board (we can supply them for you). This driver board will take your 0-5V signal and amplify it.


You can increase the ontime of the valve and run it dutycycle wise. for example.

at 1000 HZ you can run 5 volts for 1/2 ms, go to 0 for 1/2 ms to obtain 50% dutycycle.

Program your circuit for how you want it to work.

We have this working on a Haltech as low as 30 HZ. Its max frequency is 15,000 HZ

David

They call it a water injection system, but the pump is 100% methanol compatible. I am running the HSV and pump on my 240z build and controlling it via PWM with my engine management system (Wolf V500).

Hi, I'm using an AEM kit (trunk mounted) and I'm having horrible lag issues with it :confused:. I don't know if it is a controller or pump problem. Any thoughts? Thanks.

By "lag issues," do you mean the pump takes too long to reach peak pressure? I don't understand.

Sticky this mods.