how to install?

[gualicho]

hi guys im new to the site and new to water injection i own a wrx 2003 stage 4 for all that dont know what this is well is upgraded :turbo, fmic ,injectors, fuel pump, programable eng. management etc . Now i will put a 2d system got some questions on the installation: here it goes, where do i put the jets ,ive been sugested to put it on the inlet side of hot air to the fmic ( keep in mind is a fmic and not a top one , the one i have has more turbo lag and piping ) is this right? they also suggested to use 2 jets instead of one since i have up graded injectors? im not saying that what ive been told was wrong its actually the opposite is informative , but as you all know the info in the instructions is lame, also will like to know wich jet to use , single or twin jets, and at what psi should i start the water injection,also whant to know how to tune , i want to avoid detonation while adding timming and boost on pump gas wish to run 23 psi or so anyone here with experience on wrx or someone that can help i will be greately apreciated

[joeo]

Hi - I drive an MR2 with water injection. I don't think you will want to install the nozzles before the intercooler. I would install them after the IC, but before the throttle body. Is this possible on the WRX?
While water injection has benefits of cooling down the intake charge, a major benefit is if water in liquid for reaches the combustion chambers. When it state changes from a liquid to a gas it absorbs (takes) much heat away from the combustion process. This really reduces the chances of detonation. In general you want to run about 25% of fuel flow as water. When you are calculating the size/number of nozzles to use, keep in mind the pressure of the water at the nozzle and then subtract the amount of boost pressure you are running at that time.
Do you know if you will potentially be running lean with your setup? If so, you may consider running up to a 50/50 mix of distilled water and denatured alcohol. This will help richen the mixture - however to get the most prevention of detonation, nothing seems to beat straight water.
Good luck on your project - hope this has helped.

[Admin edited for link]

[Forum Admin]

With regards to injecting in front of intercooler - the water and charger temperature eventually will reach an equilibrium vapor/liquid/temperature relationship. The difference between equilibrium between the entrance to the intercooler and the valves and the equilibrium from the throttle body to valves would not vary significantly on a WRX. This is due to the long runners from the throttle body to the valves on a flat 4. Equilibrium is reached quickly - despite the very long distance from the entrance to the intercooler I do not think there would be any more evaporation prior to the valves than there would be from the throttlebody - IMO.

There likely will be no real benefit or detriment of putting a single jet at one location rather than another - with the exception of installation. Given the layout of the WRX and the best location for the installation the entrance to a FMIC is logistically a good location. If the throttle body is logistically better then no real reason to not go there.

You may want to see the experience that was had by a tuner in England while running on a dyno with one jet before the intercooler and one before the throttle body -

http://www.turboice.net/forum/viewtopic.php?t=12

[joeo]

Also - another thing to keep in mind when injecting water in front of the intercooler is that this can actually decrease the efficiency of the intercooler. By lowering the temperature of the incoming air with water the intercooler can't remove as much heat as it would normally.
IC efficiency = BI - AI / BI - outside
Where BI = before intercooler temp and AI = after intercooler temp.
I say let the IC do it's job and inject after. :-)

My setup (http://cybrina.mine.nu/MR2_Docs/Description.htm)

[Forum Admin]

I agree that injecting prior to an intercooler reduces the effectiveness of the intercooler itself since it reduces the differential that intercoolers are based on. However, if the net charge exiting the intercooler is cooler and denser I am OK that the intercooler itself wasn't as efficient. Also keep in mind that on some road cars smaller intercoolers are used primarily because in certain uses they become interheaters during long heavy loads at which point injecting before hand provides a lot of help. (Of course this is primarily experienced with TMIC not FMIC as the thread originator is using).

As an example with no thermodynamics behind it whatsoever - if my intercooler normally will drop the charge from 130 degrees to 60 degrees but injecting before the intercooler means the intercooler drops the charge from 100 degrees to 40 degrees - I don't mind that it is only working 60 degrees instead of 70 degrees. I keep or discard a pre-intercooler jet based solely on which method produces the lowest intercooler exit temperatures under the conditions it operates (drag, street, track, road).

Good to get an active thread going. :)

[MISTer MISTer]

How about introducing the mist just before the turbo? In the air cleaner tube?

I read somewhere that squirting a crude jet of water before the turbo eventually caused problems with the turbo compressor but that if one used a misting nozzle there was no bad side effects to the compressor wheel.
The person also recorded a 90 degree (F) drop in intake manifold temp
besides the usual benefit of being able to use higher boost presssures

The question is: is positioning the nozzle before the turbo a good idea? Is it the best idea?

Does the turbo compressor also benefit by the cooling mist it sucks and catapults toward the intercooler or throttle body (Cooler turbo, etc.)?

Have there been tests using this position? I'd be curious to know.


MM

[Forum Admin]

Other than what is I am sure the same reference you are making to one of the older DIY kits on the web - I am not aware of anyone else's experience with pre-turbo injection.

I think the thought of possibly eroding the leading edges pretty much put everyone off to even fiddling with the idea.

The idea is appealing. Water absorbing the heat as it is generated never building up. Not having to worry about pressure differentials at the jet.

I would want to make sure I was getting a real fine mist and only a very small amount meaning a second jet somewhere post turbo. I would also want to meter the amount of water based on MAF (are any MAF sensors linear in their signal or are they all pretty much natural log functions?).

Again it is appealing but neither I or anyone I know has been willing to take a substantive stab at it.

[joeo]

I am aware of one case where someone tried injecting water pre-turbo. It worked, but after a while the compressor wheel developed pitting. I just think it's a bad idea to inject before the turbocharger. On superchargers, I've read (Forced Induction Performance Tuning by A. Graham Bell) that injecting before the supercharger helps to seal the rotors (assuming it is a rotors type supercharger, and not a centrifugal one!), plus you get the added benefits of injecting 'pre boost'.

Keep in mind that water reaching the combustion chamber in liquid form is a real benefit to reducing detonation.

[Egoman]

With regards to pre-turbo injection, has anyone actually seen the damage caused to the impeller and directly associated it with the water injection? Is data such as water flow to cause that damage available? By this I mean seen a "good" impeller run for a while with no appreciable damage then begin to accumulate damage after installing the WI.
I am running a '60 vintage suck-through turbo setup with my injection nozzle located at the head of the system, over the carb throat, getting control input from the coil (RPM) and carb vaccuum. This application is against manufacturer recomendation, but I'm working with what I have. I am still in the process of tweaking it with regards to flow rate and trip point and would like some specifics of others experiences as guidelines. So far, I have noticed no detrimental effect and only limited benefit.
Thanks

[Forum Admin]

The only reference I have is what I read on one site about injecting before the turbo and the description of the damage and the claim of the water injection being the cause. It was sufficient to have discouraged me from trying it myself.

[Forum Admin]

Well I now have a second reference from a guy using a twin turbo that has had no apparent ill effects from injecting prior to them:

http://www.eng-tips.com/viewthread.cfm?SQID=72284&SPID=71&page=1

Towards the very end.