Water injection jet location points or where in the intake tract should I locate the water jet.
Starting from where the air enters the intake tract and ending at the intake just prior to the combustion chamber.
Location 1
Pre-Turbo water injection jet location. Jet location here is a little controversial and 99% of the WI users will not be using this location..but since the thread/subject is about water injection jet location points, it needs to be included.
Why water at this location? Water introduced here chemically alters the turbo compressor map. In other words it dynamically shifts the compressor map of the turbo so that it has the compressor map characteristics of a larger turbo. Injecting water here to achieve above has been proven...it's not speculation, boogey man stuff, or legend.
The main issue with pre-turbo......is what can happen to the compressor blade. For some, possible damage to this part makes this injection point very prohibitive.
What has been shown, is that damage can happen when having a jet location here and it's agreed that the issue is the water droplets (not misted or atomized enough) are hitting a piece of metal that is moving very fast which some would say is equal to injecting dirt/sand into or past the compressor.
Some have agreed that in order to do pre-turbo correctly you need a high quality low volume/size jet and high enough pressure to get the water as finely misted as possible. The smaller jet allows for smaller/finer water droplets = more like a fog.......think of or remember of riding a bike in the rain or the wind blowing the rain into your face, It kind of stings. Now think of riding a bike in the fog and you get the idea of what you what to try and do with a jet located here.
The one thing that is still unclear is proper placement of the jet. One thought is that if the jet is far enough away from the inlet the water mist from the jet has more time atomize and mix with the air. But, some have done this and have claimed damage. So the other thought is that water droplets are reforming in the intake prior to the turbo and it's these droplets that are doing the damage. All images of damaged compressors that have been shown show damage near the outer edges. Currently at this this time, the commonly agreed concept is to aim the finely misted water directly at the compressor nut.
IMO for SRT-4's or on other cars where stock used turbo's seem to be reasonably priced and are readily available people who are running the stock turbo could consider pre-turbo. Because of the price of a used replacement center section IF theres compressor damage, it is not that detrimental to trying it out for results that can be gained.
Also, the turn on point might need to be where the stock compressor map starts to be limited. It might be more important so it sprays only during the high boost, high heat load part of the boost cycle. Since I have not done more then reading about it I do not actually know the BEST control method for pre-turbo injection.
Richard L from Aquamist has worked on this pretty closely and has designed some jet holders that locate the jet to be directly in front of the compressor nut....really cool stuff.
Location 3
Pre-Intercooler water injection jet location. At first pre-intercooler seems like a logical jet location. The thing to think about is if the air entering the IC is pre-cooled, the ability of the IC is diminished because the smaller temp difference. The other problem is that there's a possibility that the hot air from the turbo might unnecessarily vaporize the water and take up some of the volume built up by the turbo that was supposed to be for the charge. Pre-IC does work for some track cars (road racing) that operate at a more constant higher RPM. For the daily driver, weekend racer, the pre-intercooler location should not be considered.
Location 4
Intercooler exit tank water injection jet location. The intercooler exit tank injection point is the IDEAL jet location for intake charge air temp reduction. The IC exit tank location takes advantage of the cone spray pattern of the jet...the water molecules are hitting more of the air flow then at any other point in the intake tract that the user could place the jet.
Above image shows Aquamist hard pipe adapter located in the stock SRT-4 intercooler exit tank
With Post IC jet location the idea is to cool the intake air charge as much as possible. Water molecules from a jet located here have more time to be broken down and be more fully absorbed by the charge exiting the IC before making it into the combustion chamber. This location allows for the most heat to be removed due to time and distance. Intake air charge cooling IS part of the knock problem (= high intake air charge temperature), and as most WI kits can do this simply, and other tuning methods do not need to be employed to take advantage of this location such as fuel trimming, this jet location should be the primary jet location to be considered for most WI users. Stock turbo cars CAN enjoy the benefits of a WI system with a jet here.
Location 5
Post intercooler charge pipe water injection jet location. Jet location in the cold side charge pipe is usually an easier or less intrusive jet location for most user's then the IC exit tank, but still closer to IC the better. As far as why a jet here = same as for reason given in above (location 4) other then the cone pattern of the jet is hitting air in a smaller diameter tube/pipe/hose/coupler.
Location 6
The possible issue with jet location #6 as I understand it is that water molecules here might not get evenly distributed within the intake manifold and then into the combustion chambers....meaning one or more but not all cylinders get the same amount = might be hard to tune WI properly to get the best results with this jet location. The plus of this location is that you may get bigger water molecules into the combustion chamber and get the benefit of bigger water molecules without the complexity and maybe the cost of going to port injection, plus a modified cold side pipe might be easier to replace if going back to stock, plus its easier to hide this injection point versus a port injection setup.
When my WI system was installed on my car I initially intended to just use location #4 but with just that I was not holding HOM, when I added another jet to the #6 location I was able to hold HOM. After doing this I concluded that ideally two possibly three things need to be done in order to hold HOM using WI (outside of proper tuning = plugs, wires, no boost leaks etc..). One, was to better cool the intake air charge temps down as much as possible, using a combination of toys IC sprayers and IC exit tank jet location. Two, bigger water molecules introduced into the combustion chamber. Three, reducing the amount of fuel being dumped so as not to drown the combustion chamber with liquid cooling agents (fuel, methanol, water).
A bigger IC will drop temps down but I doubt it will drop it more then the 32 degrees drop that I data logged with with IC exit tank jet location (now I could be wrong with this = I do not know this for fact). I had a full size AIS IC to compliment my setup when I was using stage III this (with a jet installed in the exit tank).
To get around possible poor water molecule distribution with jet locations close to the intake like #6 (= not in the individual ports), I have heard that a more knowledgeable tuner who is familiar with WI use one of those el cheapo tornado (forgot the exact name) devices near where #5 jet would be (inside of the cold side hose/pipe). The tuner mentioned that although the tornado device did not make power as is it is intended to do, it did help in this instance because of the way it altered the airflow, he also said that it did not negatively effect the airflow when considering the benefit it gave. So its clear I'm not saying to go out and get one of those tornado devices to be used as its been advertised................I know that a tuner did see a change reflecting what this did with the water injection.
EDIT: The image posted makes it look like the jet would be located very close to the throttlebody. In fact the jet location in the image is just to show its past the IAT sensor. A jet located too close may result in poor cyl distribution. The typical FI intake manifold is designed for dry flow not wet. If you need or want to inject closer to the combustion chamber because of the better knock suppression capabilities, then go with port injection. no closer then approx 6" is a good rule to follow and this is backed up and well documented in the nitrous community.
Location 7
The intake manifold or intake port injection jet location. Here water is being injected in a manner much like port fuel injection and it is the bigger water molecules being injected here that have a more direct effect of in cylinder cooling and injection here has more of an effect of altering the flame front of the combustion charge in a manner much like a higher octane fuel. To take full advantage of this jet location it is suggested that trimming away some of the factory dumped fuel be done. In other words, in order to take advantage of the better properties of water over fuel for cooling and injecting water at this location, you want to remove the dumped fuel and actually REPLACE this with water. This injection point with a pretty sophisticated WI control method allows for the most advantageous use of water injection. The drawback for jets located here is kit/component complexity, install complexity, additional labor, possible machine shop costs, and possible additional parts costs.
Thoughts with location close to IAT sensor
After or before the IAT is not resolved 100% at this time to say which is best or which should be done over the other hands down.
Given above, I think theres a very good benefit with a jet located at #6. I also think that this location shines when used in conjunction with a jet located at #4. Jet location #4 is better for intake air charge cooling and #6 is better for knock suppression due to the bigger water molecules. #5 IMO is for those not wanting to tap the IC at #4.....its not really because its better because of the IAT location. IF it were me and I was using only one jet it would be #4 or #5 only because I think #6 is like using a sledge hammer to get effect if used on its own. This does not mean if you or anyone else is using a single jet at #6 you should change.......what kind of system your using, what size jet, and how its tuned also comes into play as well as mixture.
Even though the PCM on the SRT-4 will make corrections to make a target point regardless of charge temp I think its good to have the PCM see the colder charge and adjust fuel, timing, and boost according to the colder charge. IMO try and keep the PCM in the loop as much as possible and use the advanced technology with in it.......in other words just improve things its working with when you can. This is my opinion and not professional tuner experience.
At some point given how low cost factory cold side pipes are around here, get another cold side pipe and try some experimenting to see if your results show a change in behavior. If you need a stock cold side to try this look in the F/S section they pop up alot. You only lose time to make the hole and swap the jet and pipe.
Altering locations to see what may work best
It's a plug for sure, but one of the benefits of the Aquamist system is the jet adapters that come standard in all of the kits, they allow you to pretty easily add in jet mounting points at a couple or several locations. The jet adapters come with blanking plugs so that moving jets around or swapping them only takes a couple of minutes.
Water injection jet location points
Linear Mode
