I just lost the reply I typed, so in brief (I applaud you on your continued interest in Pete's work given his sometimes volatile nature & expressed opinions of yourself Howard, I myself get on with him well):

I do believe that, injecting multiple fluids, pre compressor, we could realistically see up to 10% density increase at the compressor inducer, so you have 10% straight up, what I also believe wee will see is reduced turbo pumping energy required per mass flow, which is a system efficiency gain, so it is plausible to assume that we could see perhaps a 15% increase in power on a multi-fluid pre-turbo injected system against manifold/port fuel injection only on the same turbo.

My point with regards to straight water injection & map width, was that people may simply assume a mass flow improvement (as they see a higher power figure & link the two blindly) at the compressor when in actuality there may be very little to no mass air flow increase (ambient temp/density & injection - inducer path dependant), simply a reduction in required pumping power due to lesser temp rise through compression for the same mass flow, that reduction in exhaust pumping power then being seen at the crank/wheels.

 

+1

If the volumetric flow rate is limited by compressor inducer e.g. compressor is already operating at choke, only way to increase air mass flow is to decrease temperature and/or increase pressure at compressor inlet - I wonder how many people think that cold air intake and possibly ram air systems are useless on turbocharged engine

Different scenario happens when inlet isn't volumetric limited. Temperature drop in compressor diffuser (or should I say not so big temperature rise) can draw additional air mass in, so given shaft speed can produce higher mass flow and pressure ratio. (this can be observed on any compressor map - lowering of pressure ratio, in this case via lowered temperature, at given shaft speed increases mass flow to the point of choke)

Icrease in air density at compressor inlet on its own increases overall system efficiency, as desired mass flow is attained at lower pressure ratio/turbine power requirement and consequent lower pumping losses.
And of course, another possible gain happens during compression itself as the whole process is more isothermal than adiabatic. From what I have found, this technique can reduce compression work requirement by 30% which in turn will show up as lower backpressure - lower pumping losses.

But I agree, if the setup exhibits measurable increase in power, as in Tom's case, even though manifold absolute pressure, air/fuel ratio, intake temps etc. are pretty much the same (no apparent increase in air mass flow), then it must be result of net increase in system efficiency.

 

Subscribed.. haha.

good discussion. After I rebuild my motor I will try out the 50/50 water/meth injection.

Slides, your're welcome, glad to bring alot of data to the conversation. I just looked at my logs, the difference in Advanced TPS voltage is .01 volts, 4.47-4.46 volts, so ya I don't think that makes a difference, I'm sure I was holding it full throttle for both runs haha. And the power was the exact same as shown on the pre turbo wi vs post ic wi dyno graph before the power started changing after the WI started. And I guess you didn't look at the chart view of the datalogs, because the throttle went full throttle slightly sooner during the pre turbo run, less than 100 rpm difference, so again not a real difference or worth looking into because the power was the exact same until it changed alot because of the pre turbo wi.

 

I will be turning up the boost with a pre-turbo manual setup within the next few months. The system is Dudemaaaan's, and very similar to what Peter has used for years, though he seems to be controlling the nozzle with a PWM now instead of the natural progression of the system. I look forward to posting some information on my setup and results. I will be using a classic GT35R t3. I have seen them typically max on a SP rotary around 500-520whp at 25psi in C16. I know Enzo posted some good results quite a few years ago. I look forward to seeing what mine will do with water.

My plan has been to run straight water, but I too have been following Peter's thread and have highly considered running the WM50/50. I know Brent (Dudemaaaan'sownRx7) has been running 26psi with his T70 on water only. Seeing the back to back benefits of each would be intersting.

As far as pre-turbo goes, I have been sold by my reasearch. After following Pete's thread for awhile and seeing Brent's success, I went for it. Having the technical data to back it up will be a great read. I am no engineer or even tuner for that matter. But I do a fair amount of research before moving in a direction with my car. The pre-turbo setup simply works. The theory behind it makes sense, and the limited data I have seen thus far confirms it. I am looking forward to Howard's tests.

 

I am no expert, just reading here and there, but i believe if your goal is peak hp, go pre-comp WI. the drawback is increased turbo lag, as shown in tom94RX-7's thread

im thinking preturbo gives more time for the water to change phase and remove heat, which means you can inject more water pre turbo. the amount of heat removed is a function of how much water changes phase, so preturbo has more potential of removing heat

BUT.. the cost is increased turbo lag. personally, i would rather have better response over peak hp, so i plan on injecting just before the TB. i suspect a majority of the heat removal due to WI is during the compression stroke, not in the intake anyway

 

[QUOTE=gxl90rx7;11095389]I am no expert, just reading here and there, but i believe if your goal is peak hp, go pre-comp WI. the drawback is increased turbo lag, as shown in tom94RX-7's thread

+1.

+1 to the latter comment. On the stuff I've experimented with, and based on the differences I understand between water and alcohol, I can't see water doing much heat removal in the intake either. On the alcohol setup I had a few years ago, I had the two nozzles parked about 4" pre-throttle body and the air temps would soar up to and past 150*F with the engine knocking its brains out. With them moved well up-stream (one about 6" post turbo and the other 10" past that), it all seemed to work. By comparison, alcohol seems to make its change of state very quickly compared to water. I've tuned several cars that used WI in some form or another and on the ones that had post-turbo nozzles I did not see any appreciable difference in IAT's. Only with alcohol and with the nozzles parked up-stream quite a ways. I'm in agreement with you on where water's efficacy at heat removal would be because of this - in the combustion chamber.

B

 

lots of good stuff here...

i am not entirely sold on preturbo being a lag-drag. i think it is dependent on how much injectant enters the compressor when. water of course contains large amounts of negative BTUs... "latent cooling". as such, it always has an aspect of power cost. it also can be a power adder by virture of it's cooling of the compressed airmass in the turbo. cooler mass = more oxygen molecules = more power. i do think water becomes very important within the compressor housing as things are very crazy within. consider air is going thru the compressor at a very high rate of speed and yet it is going from ambient to over 300 degrees in the blink of an eye.

the water is being subjected to extreme conditions and does, IMO, create significant cooling.

i do believe water being injected in the IC piping doesn't do much cooling until it reaches the combustion chamber. there is quite a difference between being chopped to pieces by the compressor blades as well as the compression thing and just traveling along a pipe...

i think that water/meth precompressor reduces pumping effort at any level of boost.

Tom's dyno sheet seems to show lag-drag. i believe that is due to not having the proper trim of injectant under spool. if all goes well w my project i should be able to provide some relevant data as my injectant is entirely tune-able, everywhere.

i will be tuning WM50 thru the Geddy elbow w a 1000 CC fuel injector and then will switch it off and tune preturbo w a similar 1000 CC injector. further, i am using EGT thermocouples logged right after the turbo and after the IC so we will get some realtime temps.

the main point of my post however is just to say that i do not think properly trimmed pre turbo AI is a lag-drag.

there are alot of "i thinks" and "i believes" here so we will just have to see what actually happens.

my motor just passed it's coolant pressure test, the new manifold is being finished and the fuel injector fixture exists as a prototype.

howard

 

I will be installing my pre-turbo setup next weekend. I want the system fully tested and operational before I swap to my ported engine for cranking the boost up. With this, everything will be the same during my initial tests. The only change will be a slightly larger air filter, and the WI kit itself.

My plan is to log spool times before and after the kit is installed. I will post details and my findings when complete.

 

Just wondering how there would be more lag with preturbo water injection if there is no water being injected until around 14psi? I could possibly understand there would be more lag if you were spraying as soon as boost came on but I'm sure not many people setup their PTWI system this way.

A) It pays to read, lol. So it's not so much lag as it is drag when the water is being injected pre turbo.
B) Can't wait to see these Results! Keep us posted!

 

My aem water injection progressive controller was set to start spraying at about 5-6 psi and set to spray full pressure at around 15 psi I think, I'd have to double check, the rotary switch adjustments are not easy to read. My point is it doesn't start spraying full pressure at lower boost. And my aem manual recommends to start spraying at about 25% of your max boost. You can change the settings to reduce turbo lag but I think it's not a good idea to start spraying at higher boost, there will be a lag time with the water injection system too.

 

I think water micron size is going to play a very large role in pre-turbo injection, with both "lag" and compressor wear.

Theoretically, as the water droplets that the compressor is injesting get larger and larger, they will create more friction when colliding with the compresor. Thousands of these droplets together will create enough force to effect the compressors inertia and in turn effecting spool.

As these droplets get smaller, they effect the compressor less. It's all relative. If you took a water hose and sprayed it at the compressor as it tried to spool, it would struggle. If the water was a fog it would have little to no effect. Obviously these are two extremes of the volume of water we are spraying, but the physics is the same.

So what is the acceptable size?? That is the million dollar question. All foreign objects injested by the compressor will slow its inertia and affect spool. The question is, by how much. My research shows that pre-turbo desires the smallest micron as possible. So if you are using a nozzle that doesn't atomize as well, it's obvious that it will affect the system in this position. But with post turbo, it will have less affect due to the nature of that position.

So with this, if a nozzle that sprayed sub 10 micron dropplets could be tested in both locations, it would be much more accurate. The only tests I have seen thus far, are nozzles used in a pressurized pump system.

I feel air atomizing nozzles are superior at atomizing.