wes65

iTrader: (7)

Alright, I've been doing a lot of reading on the topic and I'm thinking that it sounds like a grand idea.

Injecting water before the turbo will shift the compressor map to the right. This is because the turbo is not fighting the expansion of the air as it is heated under compression. People are seeing near ambient (and sometimes below ambient) temperatures coming out of their turbo's. This effectively eliminates the need for an intercooler.

I have a 7gph nozzle on the outlet of my intercooler. I also have a 3gph nozzle that came with my kit. I am considering adding the second nozzle before the turbo. What do you guys think?

Savington

iTrader: (31)

The only problem is that it doesn't eliminate the need for an IC - you MUST remove the IC or else the water puddles in the coldside. You can't run an intercooler with pre-turbo WI.

Other than that, from what I've read, it sounds badass.

Project84

iTrader: (2)

I'm so confused.

BEFORE the turbo? So in the exhaust manifold?

OMFG my brain hurts.

wes65

iTrader: (7)

Haha not in the exhaust. Between the turbo and air filter, spraying into the compressor.

wes65

iTrader: (7)

I'd like to see an example of that. The way I see it, the hot compressor wheel spinning at 100,000 rpm will cause the water to evaporate quite quickly. I have a fairly small intercooler (20x5.5x2.5) and I do not think that the mixture would cool enough for the water to condense again. If the water were to condense, wouldn't it release the energy that was absorbed when it evaporated in the first place?

Dust

I know i am a noob, but I have been running pre-turbo injection for a month now, and the IC doesn't cause a problem. It's not a miata, but the little bit of fluid being injected, and the temp and flow will not condense the fluid unless you have a very effecient IC. The m0.5 that I am injecting gets cooked in the turbo, and hasn't showed up in my IC.

JasonC SBB

Compressor wheels suffer pitting from the impact of the droplets. Have you considered this?

Dust

Most air filters will filter down to 40 microns. DO nozzles will get finer than that. Pop on a solenoid so nothing gets out after the pump shuts off, and there sould be no problem

Honestly, for the amount of time the car will be mine, before it gets junked or the turbo dies anyway, no, i don't think it will be a problem. My main problem is drainage from not having a solenoid, and the preturbo might get disconnected because it causes my car to stumble if I get on and off it suddenly. Been looking for a solenoid to cure it.

Dust

They make exhaust water injection kits for PWCs for tuning exhaust.

PWC Water Injection System from MSD Powersports

Tedsmx5

Steam driven miata sorry.
Cool idea for the pwc though.
Ted

ZX-Tex

iTrader: (15)

This has been said here before IIRC. But from a thermal standpoint, you are better off injecting post-IC if you have an IC. If the post-compressor/pre-IC temperatures are close to ambient, then the IC is not going to exchange much heat and not be very effective. The hotter the charge is above ambient, the more thermal energy the IC will dissipate. If you keep the WI nozzle post-IC, then the pre-IC temperatures stay hot and thus the IC will more effectively exchange heat and cool the charge air. Then the WI will cool it even further.

So, when the nozzle is post-IC, the WI ends up dropping the temperature further (when measured say at the throttle) than with the nozzle pre-compressor (or anywhere pre-IC). So you get the same water vapor in the mixture, but cooler charge temperatures.

Think of it sort of like a refrigeration cycle. The air is compressed, the temperature (and pressure) rises, then the air is run through a heat exchanger (IC). The air is then re-expanded (or WI is used in our case) lowering the temperature below what it was pre-compressor. Before my fellow Engineers get in an uproar, I KNOW it is not really a refrigeration cycle, I am just making an analogy here.

If you are not going to run an IC, then I suppose the WI might as well be pre-compressor. There has been some debate as to whether or not the droplets will erode the compressor impeller. But based on my research there seem to be several on the internetz who say in their experience that it does not, at least not appreciably. It probably depends on the turbo too. My Garrett GT2871 has a very sharp leading edge on the main impeller blades so it would not take much to damage them. Other turbos have more blunt leading edges so they would not be effected as much. Some say to aim the nozzle at the shaft (lower tip speeds at the center). Some say to place the nozzle well upstream to give the water/meth more time to evaporate completely (no droplets, just increased humidity). How well this works though is going to depend on the ambient air relative humidity.

FWIW I myself am using a smallish intercooler (core is 23x6x2.5 IIRC) in my new IC setup; I have the WI located post-IC. I am also going to relocate the AIT after the WI so I can monitor/account for the WI temperature drop.

wes65

iTrader: (7)

I think you are missing the point. Heat=Wasted Energy. When the air is heated up in the turbo, it wants to expand. This counteracts what the turbo is trying to do. Therefore, the hotter the air coming out of the turbo, the harder it has to work to overcome the expansion of the hot air. This is where Pre-Turbo WI comes into play. Water comes into the turbo with the air. When the air starts to heat up, The water turns to steam and absorbs a huge amount of heat, preventing the air from heating up and trying to expand. This allows the turbo to apply its energy towards pumping more air instead of fighting with the air that it's pumping.

JasonC SBB

I think the primary benefit of WI is increased effective octane, and this comes from the effective reduced temperature of the intake charge. ZX-Tex explained that the temperature of the charge is lower if you inject post IC than before. WI can lower the charge temp below ambient, the IC cannot. If you inject pre IC the IC will not cool the charge as much and it won't go below ambient. If you inject post IC the IC will cool like before, then the WI will bring it below ambient.

magnamx-5

iTrader: (7)

nah man the real danger in situations like you have is the turbo rpm is way to high to work much further.
Im still not a fan of pre turbo WI seems like a waste to me esp if you have a front mount heat colletor.
10 gph is gonna bog your **** down agian man for real.

wes65

iTrader: (7)

You arent listening to me. I'm not denying the fact that water/meth injection cools the charge and increases octane. I am talking about the advantages of injecting BEFORE the turbo. It changes the efficiency of the turbo itself. It moves the entire compressor map the the right. This is a good thing.

wes65

iTrader: (7)

I agree that 10gph is too much. I'm thinking that i'm going to go with a 5gph at the TB and 2gph before the turbo.

wes65

iTrader: (7)

Waterinjection :: View topic - Injecting prior to turbo comp' impellers

Pre-turbo WI - NASIOC

Dust

Not trying to step on toes, but the less heat te better right. From first hand experience I have had my TMIC luke warm and IM cool on a 80F day at 80% humidity.

I know a little about the endothermic and exothermic from other discussions. Yes the water will expand to take up space that would be occupied by air, but the drop in temperature will make the air more dense, allowing more air in.

I understand the discussion of letting an IC do it's job, but there is a point where an IC is and InterHeater. Most of the turbo cars over here, and somewhat in the US are Top mount intercoolers. I can guarantee that my TMIC is useless from May to September. Lack of speed plus heat rising doesn't help. In the same vein, a FMIC sitting 7 inches above 130F asphalt is also gonna get warmer. Go WOT from the light, and your 200F will be cooled by a 120F IC. Add water/meth to decrease the outlet temps, and you have cooler air that might even be cooling the IC a bit. Put a second nozzle after the IC and before the throttle body, and you have cool pipes.

I know of the links posted by Wes65, but this one should also help too

http://forums.tdiclub.com/showthread.php?t=202520

It's about Diesels in the beggining, but some pre-turbo comes in later.

ZX-Tex

iTrader: (15)

Wes I hear you. I see how the pre-compressor injection can help. And there is evidence and theory that supports it.

One thing I had not considered is that the air is at high velocity and low pressure while it is passing through the impellers; the pressure rise comes when it is slowed down and repressurized in the compressor housing outlet section. So, while it is in the impeller section, wouldn't the pressure drop tend to cause the water vapor to condense?

We are talking about some pretty complex interactions here in the whole engine system. Improved efficiency at the compressor could mean reduced exhaust back pressure, on and on. I think the only way to know for sure is to try some dyno testing, with a given WI flow rate, in two scenarios. All post-compressor, and then a combo of pre-compressor/post-compressor.

So for example, say for a 5 gph system, test 1 would be with all 5 gph post-compressor. Test 2 would be with 4 gph post-compressor, and 1 gph pre-compressor. All else stays equal (AFR, timing). The setup with the best resulting power/torque curve wins. But the results could only be extrapolated to a small extent to anyone elses car. Changes in engine, turbo, timing, AFR, whatever, could change the results.

I think in at least my case with the GT2871 I do not want to push my map much further to the right! If I had my GT2560 still it would certainly be worth a try since with this motor I would be able to push it well into the right side of the map, and thus the map shift to the right resulting from pre-compressor WI would be beneficial. As mentioned, it could end up in a win-win scenario, fast spool with the small turbo, but improved efficiency with the WI.

Good discussion so far, and good links. OK, break time over, back to the garage. Gotta get this IC installed

magnamx-5

iTrader: (7)

that makes more sense i wonder where you got the idea to run two nozzles on staged injection Im curius as to the amount of pooling etc you get. Theoretically if you kept the spray off until you hit a higher velocity say 13 or so psi it should all keep on moving until your done with it in the combustion chamber.