Dark Lightning

I'd try to have the water injection activate at whatever pressure you see at redline. So, if you have a K26 hitting 18psi but falling to 12psi then I'd set your pressure switch to 12psi. If you look at datalogs for 944 Turbos with that boost curve (basically pushing the stock turbo to the wall) the airflow for 3500 to 7000rpm is straight and level enough to play billiards on, and the injector duty cycle mirrors the airflow.

jasoncoker

Hey Guys,

Thanks for the feedback. The system is a Snow stage one which uses an on/off pressure switch rather than a true MAP sensor. The switch is adjustable. The Stage two kit is the same as mine except that it has a completely variable controller that varies the amount of water injected according to boost pressure. I assume that it uses a MAP for this.

Initially, I left the switch setting as is. I think that it was injecting at about 4 psi or something ridiculous. It still did not stumble or anything which I found surprising. For the dyno runs I think it was injecting around 7 psi. I increased it now to about 10 psi. It seems to work well.

That sounds like good logic, Lightning. I may try it out. I doubt I will notice any difference, but I am going through so much washer fluid right now.
I think that my jet is too big. I went on an aggressive canyon run Sat. morning and went through about 1/2 tank of gas and a gallon of washer fluid. I think about 10% water to fuel (MAYBE up to 15%) would be good. Obviously, I was not on boost the whole time, so I think that I am injecting too much.

I do not know the exact size of my jet, since I did not buy the kit new (although it was new). The stupid jets are not labeled, but I think that it is a 225ml jet. I also do not know the pump output pressure which also changes the amount. So, basically I just threw this all together and it seemed to work okay.

Sincerely,
j

FSAEracer03

I don't see why you'd wait until the a/f leveled off... it would never be in use! The water to fuel idea isn't a set in stone concept that needs to have X.XX% water for fuel. Remember, the "water" injected isn't making it into the chamber as droplets! The purpose of water injection is to quench the intake charge and combustion chamber's temperatures in order to reduce knock, allow a more effiecent, turbulent burn and get more air into the chamber.

I'd say have it set at boost threshhold. It really should be throttle with boost and rpm, but if you can't give it a little extra window. 3500 to redline should be a good range and might even help to cure the wild a/f range. It sure cleaned up a 930 under development by my buddy. www.heibar.com

Don't be foolhearty with water, but my all means, don't be bashful. Good luck on the system.

-Kevin-

NZ951

You would want it when its levelled because you are trying to maintain a ratio of fuel to water. Though its not set in stone as you suggest, you would not want to add what is proportionately a LOT more water at say 1-5psi of boost over 10-15 for example. Why do you think the Stage 2 has the controller to vary flow? As do most all other advanced systems such as Aquamist.

Only the Link computer I am going to get, you can have up to 3 variables to contrl a PWM output. Ie boost at X with TPS at Y and RPM at Z, then A will occur.

eclou

Resurrecting this thread since I am getting ready to install my Snow kit. Has anyone else had any new issues with injection? I am thinking about tapping into the hardpipe rather than the outlet of the IC just incase since it is cheaper to replace a hardpipe

jacklet

you can tap it at the hardpipe

tedesco

Hi, interesting subject. If I see right on the pictures, you put the water injector behind the intercooler. Wouldn´t the cooling effect be bigger if you inject directly at the turbo outlet, means well infront of the intercooler? First stage of cooling would be the water injection where the evaporisation can give you the best cooling effect due to the air temperature beeing highest directly after the compressor outlet (and high enough to realy evaporate the water). The second stage would be the intercooler that just does the last bit to come as close to ambient as possible.
The old F1 cars proceeded in a similar way where the first stage was an air to water intercooler and the second stage was an air to air type. This was an advantage even due to the additional wheight and compexity of the setup but got banned after some time. The reason it worked so well is the superior heat transfere from air to water compared to air to air. Still the boundarys were quite different than for a modded 944 with boost beeing set to around 6bar and all kinds of "special" ingredients beeing injected.

toddk911

"You actually made HP by adding water and not boost or timing? Thats pretty interesting,"

Cooler charge air = more hp.

toddk911

"EDIT: I can't see the torque increase (the good stuff). My buddy's system got ~15hp gain from just water (no, it's not a cheap system) but saw a torque gain of almost 60lb-ft just from water addition on a bone stock 951!"

AWESOME!! he have the dyno for that?

Maybe people in here will finally admit water/alch/meth works and is no joke.

I have said PLENTY of times. I would rather spend 200-300 on WI then new IC or splitter which yield little results. At least in cost vs. results.

toddk911

"I am injecting into the intercooler endtank on the "air out" side. Injecting before the intercooler creates a problem with the water vapor recondensing inside the intercooler as the air going through it is cooled."

But then that acts as a IC sprayer/cooler as well.

Best results are twin injection, 1 before IC which cools the IC and 1 after.

jasoncoker

Hey Guys,

In my opinion, the hard pipe is too thin to tap and mount the nozzle into and not have it leak. To do it right, I would have a bung welded into it. Nevertheless, it would be easy enough to try it first and then, if it leaks, put the bung in. If not, cool--you're done.

Injecting water before (and after) the intercooler on F1 cars in interesting, but I am not sure that we can directly apply their findings to our cars. Weren't they running 50+ lbs of boost on the F1 cars? Well, no matter. Pre-intercooler injection may work fine.

In the interest of keeping the setup simple, though, I think it is easiest/best to mount the nozzle after the intercooler if not doing a dual sprayer setup. Remember, this is the most basic stage one system. If engineering finesse were the goal, I would use port water injection.

Tedesco's point that the highest temperature differential increases the efficiency of water atomization works for the intercooler as well. The hotter the air entering the intercooler is, the greater amount it will be cooled. That is not to say it will be the same temp when it exits, only that the temperature drop will be greater. Since the intercooler cools with ambient air, this matters even more. Intake air at 250 degrees may cool to 150 degrees by exit (100 degree drop), but intake air at 150 degrees may cool to 100 (50 degree drop) at exit. That is significant because now you have to push cooler, denser air through the intercooler. Also, cooling the air at the intercooler end tank may decrease pressure at that point (P=(nRT)/V) helping to pull air through the intercooler. Maybe pull is too strong a word, but at least decrease pressure drop somewhat. Finally, that 150 degree air will now vaporize the water better before entering the engine.

The fact that the intercooler uses ambient air is key, b/c under most circumstances (at least in Los Angeles), it is not all that cold outside. When I first put in the setup, I went around the neighborhood for a while getting the pump to come on a lot. I then came back into the garage and put my hand on the intercooler out pipe. It was cold to the touch--significantly cooler than ambient temperature. Had I injected before the intercooler, I might have actually heated up the air. Haha, an interheater.

Oh, all of the intake temp numbers above were made up to illustrate my points. I just put the kit on and used it in a simple installation. It would be interesting to see others' results with pre and post intercooler setup. I would be a little surprised if it were worth the effort involved in balancing nozzle sizes and equalizing pressure to each (due to different pump distances and also the higher pressure in the turbo out pipe than in the intercooler out pipe). If anyone has results for this I would be interested to see it.

Well, those are some of my opinions on it all. I hope this helps someone.

Sincerely,
j

__________________
'89 Turbo

tedesco

Hi Jason, maybe I was not precise enough in my describtion. Certainly the temperaturdifference will influence the heat transfere from one medium to another but this is not the only factor. The heat capacity of the mediums involved is important too and THIS is the reason for having an air to water intercooler before the air to air intercooler. Water has a lot higher heat capacity than air which means with compareably little water you can cool down a lot of air which than also keeps the temperature difference big => an example:
to cool down 1kg of air from 200° to 120° it might need 200gr of water increasing temperature from 20° to 40° (final delta of air out to water out = 120°-40°=80° is easy!). This is just an example and I would need to look up the exact numbers. If you want to cool down the same amount of air (1kg) from 200° to 120° with 1Kg of air (you would not be able to do that with only 200gr) as cooling medium entering at 20° it would finaly need to end up at 100° which corrosponds finla delta of air out to air out of just 120°-100°=20° a lot smaller difference not so easy=>bigger radiaor needed). This is tougher. Difference beein only the heat capacity of the medium used. Conclusion: It matters a lot if you run first through the water intercooler and than through the air to air or to do the other way around. Water first and you devinetly reach lower charge air temperatures and this is the reason it was done on F1 cars in the (good old) past.

Anyway, this was not the topic but is also related to my arguments for injecting water before the intercooler. If the water starts to condensate in the intercooler it is only a sign of already low temps only due to the water injection. Just keep a trace of the intake temps and reduce the amount of water you inject. If it condenses in the intercooler how do you expect the water to evaporate if you inject all water after the intercooler ( a bit simplified but you get the point)? The water injection is just less effective and you need more for the same cooling effect which might drop HP because now also the water content in the charge is higher and water does not burn!

At the end an experiment you can do easy at home (if you like coffee with milk):
brew two cups of coffee (use equal cups)
directly top up one cup with some milk
the second you let rest for 2 min
add the same amount of milk to the coffee than you used in the other cup
drink from both cups

What you will notice is that the cup to which you direcly added the milk is hotter than the coffee from the other cup. Reason for that is that if you directly add the milk (=air to air intercooler first) the water of the coffee does not evaporate any more and loses little heat due to this.
In the other cup the coffee was still very hot at the start so that the water could evaporate (water injection before the intercooler=>evaporation). When you finaly add the milk it just gives a final cool down to the already cooler coffee (air to air intercooler).

I hope you at least got a smile after reading...

jasoncoker

That is interesting, and I definitely did smile. Good stuff.

I understand that the specific heat capacity of H20 is greater than air (Q=mc delta T), which explains the efficiency of air to water intercoolers. The thing that really works in the water injection (as I understand it) is the phase change from liquid to gas (and the consequent high latent heat of evaporation of water). This does not occur in either an air/air or air/water intercooler. I think it is a bit of an apples to oranges comparison. I think engineering an additional air/water intercooler with lines and a pump is beyond the scope of just a basic, do-it-yourself water injection kit.

Nevertheless, I think that we are both using sound science to arrive at more or less correct, but different, conclusions (is that even possible?). The cool air at the end of intercooler helping air through vs. the advantage of cooling the air earlier as it relates to ultimate cooling with less water used. Hmm, I dunno which has a greater effect ultimately.

One thing I DO know for sure, is that it is easier to inject it via a nozzle in the endtank and not worry about it. Haha.

Thanks for the input--I may try the coffee thing one of these days.

jasoncoker

I just found this handy dandy curve:


The diagram on the left shows the uptake of heat by 1 kg of water, as it passes from ice at -50 ºC to steam at temperatures above 100 ºC, affects the temperature of the sample.

A: Rise in temperature as ice absorbs heat.
B: Absorption of latent heat of fusion.
C: Rise in temperature as liquid water absorbs heat.
D: Water boils and absorbs latent heat of vaporization.
E: Steam absorbs heat and thus increases its temperature.

The above is an example of a heating curve. One could reverse the process, and obtain a cooling curve. The flat portions of such curves indicate the phase changes

Please note how much more energy is absorbed during the phase change vs. just cooling while in the same phase. This is the difference between the intercooler efficiency and the vaporization of the H20 injection. I think that the energy drop is based on the mass of the water, not the temperature of the air vaporizing it. This would mean that as long as the water gets completely vaporized, it should not matter where it is injected. As stated before, this is not the case with an air:air intercooler which works in area C instead of D.

At least that is the way I see it. I can see Tedesco's side of it as well. I don't know which would ultimately work the best.

I would never presume to understand this more than an F1 engineer, though! haha

I will check in tomorrow night--bye.

Sincerely,
j

toddk911

Then with the water/methanal mix, you can get it down to sub freezing temps before filling up