Interesting concept!

You would also have the issue of ice crystals forming during the evaporation process, the alcohol will evaporate more rapidly than the water so you get a distillation process as the mist moves down stream. An ice crystals that form would have a more agressive errosive effect on the compressor than the liquid water, so that is one issue to avoid.

With Propane injection you also have a balancing act going on between charge density due to cooling and oxygen dilution by the propane. This increases the volume of gas that must be compressed. As a result of that I would think you are looking for a happy medium where you get the benefits of some charge cooling, some increase in fuel octane, and better vaporization in the combustion chamber without over diluting the intake charge the turbo needs to compress.

Like you mention the cooling effect occurs at the point the liquid changes to gas, so by moving the solenoid to the injection point the cooling would move to the nozzle.
years ago I used to work in a gas station and one of my dutied every night was to blow off the compressed air in a pressure washer tank. In that case the point of expansion was at the outlet valve and that is where the frost formed. It might be ideal in your application to run the liquid propane through a heat exchanger as it expands to capture that cooling power and use a finned heat sink to cool the air charge.

Larry

Can you expand upon this Larry, and tell me how the heat exchanger would be linked to cool the air charge.

Just brain storming a bit.

First you would need to do a bit of experimentation to find out how much cooling occurs near the solenoid and the line between it and the spray nozzle. If that section of line gets really cold you could wrap it in a coil around a segment of tubing and insulate the outside and put some fins on the inside. If that was placed in line with the air intake it would help cool the air charge by using cooling from the expanding propane that would normally be wasted.

If most of the cooling occurs at the propane bottle you would need to determine if there was any practical way to use that cooling to pre-cool the intake air by passing the air charge around the propane bottle. I can imagine a way to do it if you were using the smaller consumer propane bottles intended for propane torches, but not if you were using a proper DOT rated propane bottle in the trunk.

You could also use a wasted propane (or nitrous/CO2) system that just blew off some of the propane, nitrous or CO2 through a heat exchanger, but that would add some concerns about where the extra propane goes and would it be a fire hazard. This would be similar to the cryo cooler systems.

Larry

What if I injected methanol only? -40 wouldn't freeze alcohol right? I find this stuff interesting but I don't understand physics at all. Water has the ability to absorb far more latent heat than alcohol, but alcohol evaporates faster! So which is better in this situation?

It depends on the efficiency of your compressors and the effectiveness of your current intercooling (as well as how often your cylinder pressures exceed 'safe' levels, mainly Compression Ratio relating to boost)
You might want mostly alcohol before the cylinders and mostly water into the cylinders.

i have only ever used total pre turbo injection (15% of fuel flow).

what i have noticed is no negative performance difference in heat exchanger, mostly increases

same boost
no WI 59deg c charge at end of 400m test
with pre turbo WI 45to 47 deg c same test

the water may boil in compressor but it condenses again leading into IC and def out of it, i can see suspended water vapour clouds in charge pressurized water tank which takes feed just before throttle body. So i get the turbo efficency increase and also in chamber cooling as well for what i have seen.

in practice have run up to 28psi boost on 9:1 comp wankel engine where others are limited to around 20psi maximum on very heavy AFR's and retarded timing, so it def seems to be working. power is there too over different cars which means its not a one off fluke result.

i use a special water/air atomizer on my "ghetto" systems, as a result no compressor wear at all after many 1000's of km in field use. hope thats of some use ?

Very nice :smile:

Could you shed some more light on this "atomizer?" A website or picture possibly? I'm just curious as to what others are using for nozzles for pre-compressor injection.

So much good information here, but no recent follow-up.

http://www.spray.com.au/ss-redir-prod.htm
if you look under the catalogue you will find some info on the SUE18
and the SUE25BDF that others use

go catalogue> air atomizing nozzles>18J and 14J series
than they are either in pressure spray setups- internal mix
pressure spray setups- external mix
cheers
darren

Theory:-

i) By using a turbo exhaust housing with a smaller AR we can help a large turbo spool faster, but the trade off is that the housing is unlikely to be able to flow enough air in the upper rpms to be able to realize the full potential of the compressor.

ii) By using pre-turbo water injection to move compression away from adiabatic towards isothermic we improve compressor efficiency enabling it to flow more air.

Question:-

If we reach a point whereby the exhaust housing is already creating a restriction to airflow, will pre-turbo injection

a) Have NO noticeable effect because the housing is unable to support any further increase in flow?; OR

b) Make the air denser thereby allowing more air to pass through the housing?

I would also like to get hold of a table to give me an idea of what sort of volume of flow I can expect from running an air atomizer nozzle with 150 psi of liquid pressure and 400 psi of air/gas pressure.

I'm concerned that liquid flow will be dramatically reduced as a result of the very high pressure. I looked at the nozzles Darren posted and at 60 psi of liquid pressure, flow was reduced from 2.28 gph at 50 psi of air pressure to 1.11 gph at 70 psi.

Precompressor injection sees no boost because it takes place always under mild vacuum (before the compressors obviously!)
So the pump not flowing enough is not really a problem.
Good atomisation and aiming at the eye of the compressor are more important considerations.

Okay, so that might still work then. What about my post above. The consensus previously seemed to be that this was only really beneficial for a compressor that was being maxed out and was unable to flow any more air. What about the situation I described where the restriction is the size of the exhaust housing. Will making the air denser allow me to push more through a smaller aperture. In theory it seems logical that it would but I'm wondering if the end result will be as effective as on a compressor that is reaching the end of it's efficiency threshold.

The thing is that whilst I understand that one of the main reasons that this works on smaller compressors is because they start to generate so much heat when they move out of their efficiency island, it also seems highly likely that where the exhaust housing is 'too' small, similar problems of heat and friction are going to occur where the big turbo is forcing more air into the housing that can pass the restriction. I'm sure that cooling the charge air and making it denser would have an affect here, I'm just not sure how much.

If anyone can spread some info here I'd be very grateful. I'm intending to use a Holset turbo on my application because of the turbo's durability and it's reputation for spooling quickly. The main criticism that is levelled against the turbo with the smaller exhaust housing however is that it loses between 50-100hp of it's full potential at the upper rpm range as a trade off for the very fast spool up of such a large turbo.

The possibilty of having a 65 lb/min turbo reaching 22 psi by 3500 rpms or sooner and making 600 hp is pretty exciting.

We'd need good experimental data for a this.
I've not come across any.
Indeed :smile:

Based on my experience I would "guess" that the answer is it may help some.
It makes the compressor more effecient (it takes less work to reach a given flow)
That implies that there will be less resistance for the turbine to overcome to reach a given flow so it should spool a bit quicker.

I know in my setup when the pre-compressor injection was working the turbo seemed to hit very hard when it turned on.
Sooooo the seat of the pants dyno says it might work but only some before and after testing would give you solid data to work with.

If I remember the NACA studies correctly at 3% water to air flow by weight the compressor flow increased about 10% over its normal flow, so I would think it would not be unreasonable to think the compressor should come on boost 10% quicker. If you hit full boost at 3500 rpm without it then perhaps you would get to full boost at 3200 with the injection.

Only my gut reaction but it sounds reasonable to me.

Larry

That's very interesting, but that brings two things to mind;

1) My initial reason for doing this was to see if I could gain any of the power back at the top end that this turbo allegedly loses from using a smaller exhaust housing. The basic problem is that whilst the turbo flows 65 lb/min at it's peak, the exhaust housing might flow lets say only 52-55 lb/min. So I'm just not sure if using water injection is going to bring the 55 lb/min threshold on earlier giving me less rpms in my powerband or if the air being denser means the smaller exhaust housing my be able to flow more than 55 lb/min if the air is denser and therefore more condensed/compressed. Surely it stands to reason that 55 lbs of heated air is going to take up more space than 55 lbs of denser, saturated, cooler air?

2) Bringing spool on quicker is something I hadn't considered but if I were to use this method, I had not initially intended having the water injection come on so early. If it was boost activated the activation point would have to be very low, perhaps 5-7 psi or perhaps rpm based. Making it rpm based would however not take into account different loads and airflow in different gears. I wonder if an airflow based activation point run off the MAS/MAF would be worthwhile?

I also intended to run the water in a mixer nozzle with propane injection. I'm not sure if injecting propane at such low rpms is a good idea in which case I'd need to consider a liquid only system or maybe an air based pump.

For top end mass flow through the hot side your best bet is to try to keep the exhaust gas as hot as possible to bump up the choke flow point as high as you can. That might mean leaning things out a bit, or playing with ignition timing.

It's really hard to speculate without any hard data. I triggered my pre-compressor injection strictly off of manifold pressure.
On my second generation setup I was going to use both an RPM window switch and the MAP to do it so I was sure mixture speed in the inlet tract was maxed out before I started the pre-compressor injection.

If you have a simple means to do it, a mass air flow sensor input would probably be ideal as it would self adjust for rpm and boost and all those other variables.

Larry

Alright, I'm going to need some help here. On the face of it it looks as if I can get a 60 psi compressor running off 12V DC (draw on the electrical system will have to be evaluated) which I can use to do this. What is really doing my head in here is trying to calculate flow. What really messes things up is that in air atomization nozzles (which seem to produce the smallest water droplets) increasing air pressure will reduce the amount of water flow (presumably because of the liquid that the air displaces).

Now given that the tables for these nozzles suggest water pressure of around 50-70 psi and a Shurflo pump will produce around 100-150 psi we should be able to increase liquid flow, but would this then require a higher air pressure to successfully atomize the increased volume of water? Is 60 psi of air enough or should I be looking at more? I have located a 100 psi air pump but it flows less volume of air. I still can't get my head around whether pressure or volume is most critical for atomization.

There are probably too many variables here for anyone to give me a straight answer, but can someone point me in the right direction. Someone said that good atomization rather than flow is the key, but a certain amount of flow will presumably be necessary to pull sufficient heat out to make the compression isothermic (or as close to isothermic as possible).

So lets just look at flow for a moment. I can bench test how much water the system flows in a min, by experimenting with air and water pressures.

I have a 2.3 litre engine and a turbo rated at approximately 65 lbs/min (however that may have been reduced by the fitment of the smaller exhaust housing). How much water do I need to do what I am trying to do and would the volume of water injected need to be different if I set the injection point much lower in order to assist in spool up.

I have a lot of this stuff figured out and can do it, but I really need help working out the flow calculations.

My other concerns are: -

(a) Will injecting too much water cause it to puddle in the intercooler creating problems?
(b) Will it be necessary to inject more water post intercooler for knock suppression?

If you are injecting pre-compressor at 2%-3% rate compared to air flow you will have about all the WI you need.

Suppose you spray at 2% air flow rate, and you have a 11.5:1 fuel air ratio at red line.

If you are flowing 65 lb/min, that is 29510 grams of air per min.
At 2% flow that means you would be injecting 590 grams / min of water.

If you have an 11.5:1 air fuel ratio than your fuel is 29510/11.5 = 2566 grams / min
Since most gasoline has a density of about .78 then that is 3289 cc/min
10% water to fuel would be 329 cc/min
15% water to fuel would be 493 cc/min


You would be spraying about 18% per min to fuel if you sprayed 2% of air by weight with a max power AFR of 11.5:1.

The beauty of using the air flow is is self corrects as you lean out the fuel.
the higher your AFR (say 12.5:1) the higher your percentage of water/fuel at a fixed water to air ratio.

Since many engines will report mass air flow directly in grams /sec it is trivial to find 2% of your max air flow in grams per min, which directly converts to water flow in cc/min.

If you delay WI turn on until 10 psi Manifold pressure or so the turbo will be well spooled before the water comes on.

Bottom line:
(a) Will injecting too much water cause it to puddle in the intercooler creating problems? --- possibly but that would quickly evaporate as the intercooler cools down as long as it was not a huge amount of over spray.


(b) Will it be necessary to inject more water post intercooler for knock suppression?
Probably not in my opinion.

On the atomizing nozzles I've looked up they most only need to have about 30 psi air supply pressure to work properly.
Not sure why you would want to run such high pressure unless you tapping a pre-existing high pressure supply.
Larry

Larry thanks that really helps!

I guess I just figured higher pressure would atomize the water better. I know if you start getting paranoid about injecting water pre compressor you shouldn't do it. The problem is I have a brand new $1000 turbo about to go on the engine and I really want great atomization to avoid problems.

Had another thought. If you are using a MAF in draw through and injecting pre compressor with an atomizer nozzle, won't the air you inject be unmetered and make you go lean?

Pre-Compressor Injection Advice
 

I completed my pre-compressor injection set up a couple of weeks ago on my 2003 Lancer Evolution VIII. I am still running the stock 16G turbo and am using a .3mm pre-compressor nozzle mounted on a custom axial mount. The .3mm nozzle that I?m using is an unreleased nozzle that Richard supplied me to experiment with. It has an internal progressive spring loaded valve so it opens about 2-3 psi later than my primary post intercooler .7mm nozzle. The .7mm is set to come on at 13 psi, so I figure that the pre-comp nozzle is spraying at about 15-16 psi. The maximum peak psi I see is 22-23 psi and it tapers down to 18 psi by redline. Here?s a link to pictures of my installation if anybody would like to check it out: http://www.aquamist.co.uk/phpBB2/viewtopic.php?t=654

I was able to go to my local Dragstrip yesterday to see what sort of results I would find. Unfortunately, my car fell off in power. I usually run 12.80?s @ 104-105 mph. My first pass was a 13.27 @ 100 mph. I then richened up my air/fuel mixture a little thinking that I may have leaned out with the pre-comp injection. I ran even worse, a 13.48 @ 99 mph. I decided to disconnect the pre-comp nozzle and run again on my regular .7mm post intercooler nozzle along with my previous fuel map. The car responded to a 12.90 @ 104 mph. The car was acting like the engine was receiving too much water mixture. My thoughts were that by using a small .3mm pre-comp injection nozzle, the water mixture would have evaporated by the time it exited the turbo. I was going to reduce the nozzle size post intercooler to see if the car would respond, but unfortunately the track was closed shortly after due to high winds. I?m hoping that maybe some of you that have had more experience with pre-compressor injection could offer some advice.

This is a very good practical example of the pre-T injection.

Such a small amount of spray has such big effect, a mystery yet to be fully exploited! Pity you cannot complete more test before track is shut.

You might find it would be better to cut back the size of you post intercooler jet to about a.5mm.
I found that in my setup I was over spraying quite a bit and have kept reducing the size of my pre-compressor jet.
I started with 4 gal/hr (240-250 ml/min) and ended up using a 2 gal/hr (120 ml/min) and I still think I was using a bit too much. I am re-engineering my setup and will be trying a couple other options.
I want to set the pre-compressor injection up so it only comes on at high boost pressure so I am planning on put a boost switch and another solenoid on the pre-compressor jet so it only comes on at boost pressures that I know will be maxing out the turbo's air flow (around 20 psi + ).

Larry

Larry, thanks for the response. I'll try a .5mm nozzle since I have one on hand. I also have a .4mm and .6mm also to play with. The only thing that concerns me is that since I was tuned for a .7mm post intercooler nozzle and a .5mm nozzle may run slightly lean for a moment until the pre-comp nozzle kicks in. The engine just had the symptoms of too much water mixture being ingested and reducing the post intercooler nozzle definitely makes sense. The first chance I get, I'll hit the dragstrip again. Luckily the track was kind enough to give the racers a free race pass for having to close down the track early so I can return and tune for free :smile:

Joe

How did the car react when you were spraying too much pre-compressor through the turbo? Similar to an overly rich condition, where the car stumbles and chugs a bit? Did it hamper spool or boost response at all?

I ask because I've got a 3 gal/min nozzle planned for my pre-compressor setup and don't want to be spraying too much right out of the gate.

Re: Pre-Compressor Injection Advice
 

joe, i have a question about your setup...

you say that the pre comp nozzle has an internal spring valve that causes it to open 2-3psi "later" than the other nozzles in the car. i can't see how this spring valve inside the nozzle would be opening with 2-3psi more BOOST--it doesn't "see" the boost at all... it sees the pre compressor inlet pressure on one side, and the water injection pump's output rail on the other.

i CAN see the valve opening up once the RAIL pressure is 2-3psi higher than when the other nozzle(s) open up.

perhaps richard can chime in here and offer some insight as to the construction/use of the prototype nozzle?

the other advantage i can see to an internal 2-3psi check valve would be a decreased tendency to drip after flow is ceased... a "good thing" particularly pre compressor.

in any event, thanks for posting up your experience,
ken

Re: Pre-Compressor Injection Advice
 

Ken, I'll have to have Richard explain more about the nozzle design.

Re: Pre-Compressor Injection Advice
 

I believe joe was trying to say the 0.3mm (pre-turbo), spraying at 65cc/min comes on at 15psi due to an inline 15psi checkvalve being installed. If his car is boosting 12psi, the 0.3mm will come on at 15 psi. The 0.3mm nozzle is a standard aquamist nozzle with a 25um filiter inside.

Having only just managed 14 pages of posts in my first read, maybe I should apologise for posting a reply/comment prematurely... but won't, as this is such a necessary and compelling thread! And I think I might be able to fill out some aerodynamic theory, as a lot of my thermodynamics has gone the way of the wind and tide :smile:

The step at the compressor inlet is almost certainly there to trip the boundary layer - if it's still laminar (likely), to fully turbulent. Many misconceptions around (not suggesting here, particularly) about laminar/turbulent boundary layers and separated/non-separated flow regimes - they're inter-related but very different things...

I've seen Mach No. (M), mentioned, it's important, but unless I missed it or comes after Page 14, not Reynolds No (Re), this being another non-dimensional parameter that determines the ratio of kinetic to viscous energy in the flow, and has a profound effect on boundary layer and flow separation. And of course the operation of turbo-machinery, as well as heat-exchange...

The effective Reynolds No. (Re) is low - and in turbo-machinery terms, perhaps very low, as the characteristic size of vehicle turbos is small (inlet hose diameter, impeller diameter) until things are changed dramatically as the flow really picks up speed (and is then immediately diffused).

We're talking 'dimpled' golf-ball behaviour here, where the payoff in delayed separation at the rear of a bluff body easily outweighs any extra frictional drag from a thick non-laminar boundary layer.

Suffice to say, that I'm not contributing directly to the debate on pre/post compressor WI, but suggesting that it might be worth establishing what's going on aerodynamically before the really complex bit - entry into the world of high-speed, but very small-scale turbo-machinery.

One possibility, is that a boundary-layer trip a bit further back up the inlet hose, might well help evaporation if injection is taking place well before the impellere eye - a wire, glued circumferentially around the inside of the hose, might do the trick... pulling flow energy down onto the surface (turbulent bl's have a much higher exchange of energy between the surface and their outermost extent).

One other point is a few mentions back there of sharp turns in the hose just before the turbo-compresor inlet... and a few raised eyebrows perhaps? Whilst a reasonably tight 90 degree bend probably isn't too much of a flow impediment, a common solution when a really tight bend is necessary is a banjo style design. An enlarged radius just prior to compressor entry being fed from the inlet hose at right angles to it - if that is a good enough picture in words. Acts a bit like a settling chamber before the flow changes direction

I have such a banjo elbow on my candidate vehicle (due an engine mounting within 4 or 5 inches of the compresor inlet), and thinking about it, might present an ideal area to inject straight into the impeller's eye from just a few inches away...

Enuff for now, must read-on...

That added another dimension to the myth of pre-T injection.

It appeared people is getting mix results.

OMG, I made it through all 24 pages... it took me a week at work - seriously, not a full time week, but 'when i have time week'.
some really good info here, but then again, there's some misrepresentation going on. Mind you might might be slightly off topic.

Particulary I want to comment on turbo sizing.

Everybody here seems to be talking about the compressor, and compressor maps, etc. Turbo is made of two parts compressor and turbine. they are conected by a common shaft therefore turbine is as important in making power as compressor being drive by that turbine. Nobody mentioned manifold design/type...

Exhaust housing size is mentioned in only 2 posts in the whle thread, while it is a very important factor.
Exhaust housing size, along with manifold sizing/design and exhaust system greatly affect power and responsiveness of the engin.
Assume good manifold deskign (tulbural, no sharp turns, equal length, full split pulse separation, with 2 wastegates) and ample exhaust system used.
The bigger the exhaust housing the less restrictive the exhaust gasses path, therefore greater power putput. That is aswell compounded by the fact that less restriction lowers EGT's therefore raises knock treshold.

it is common that oem turbo setups usually use smaller exhaust housing as that produces a quick throttle response making car feel more powerfull than it actually is...

ok, ok, where i'm getting at, with regards to pre turbo WI.
I'm saying that all thought I agree with the fact that preT injection will incerase flow of the compressor, i think the because air is dense, compressor is harder to turn therefore is turbine and that is more resistance to the engine.

And if your turbo is outside of efficency range, wi might incerase air flow, but chances are that your exhaust housing is maxed out in terms of flow therefore more air will not make much more power.

Many people here seem to confuse boost with power. power is a function of much much power is made in cylinders and how much is lost for running rngine (resistance of bearings, inertial losses on pistons which are constantly accelerating up and down, resistance of the exhaust gas flow. Generally speaking in a healty setup should produce nearly 200% of it's NA power at 1 bar of boost (i.e. 2 bat absolute pressure). and it's not exacly 100% per 1 bar, but as you incerase the boost you should see incerase in power. keep incerasing boost further and you will eventually get to the point of diminshing returns, where more boost doe not produce as much more power as at lower levels. so you work out a happy safe spot for you or look what can be changed to make that boost range more efficient... bigger exhaust housing, more efficient compressor, etc...

I guess what I'm saying is that with small oem setup type turbo your tuning abilities are limited because of the size of the turbo. and normally stock manifolds are cast and generally pretty bad design (see twin turbo supra stock manifold).

but with building efficient systems (low exhaust restrictions) great efficiency can be obtained. taking that idea to new level, there are some great benefits when we reac the point when boost pressure is higher than exhaust backpressure... then you can use wild cams on turbo motors, and that allows you to spool large turbos with small engine with great efficiency.... a example of bad way to do it is the 800hp skyline mentioned earlier in this thread which at 3 bar makes less power than at 2 bar. too small compressors ? possily. exhaust restrictions must be huge. pumping more air will not solve the problem. get exhaust housings 2-4 sizes larger and it will make 900 on the same boost... they will spool a bit later tho...

I think water (and other pre turbo injection) has it's place and should be further researched. But results may vary in every case. It seems like ideal candidate would be turbos with smallish compressor but large turbine... where compressor is limiting factor of the system... cooling charge air by convection (evaporatino of water or other fluid) is a way to go i think, but needs more experimentation...

I was thinking... maybe along with spraying large quantities of methanol, inject pure oxygen to the intake tract... yes, it might be expensive but power gains might be great too.... would work good on drag cars...

Just getting familiar with this topic again, after being away for a year.

I am seeing some questions and observations that don't have answers, and I thought I would get involved. I have spent much of the last year working through a problem with coolant overheating on GM diesel work vehicles. Since some of my findings are applicable to this effort, I will elaborate.

What I found was that the smallish compressor was working in the northeast part of the map, and in some thermal conditions, "off the page". On further investigation, the temperature of the compressure discharge emerged at near 600 F. I calculated efficiency around the 50% mark. Needless to say, this is in a word, ridiculous! Further investigation led me to question what the effect of this heatup (and expansion) is on the downstream plumbing. Something told me that I was seeing extaordinary head losses with this huge heatup. In other words, the velocity in the IC/CAC plumbing would be increasing dramatically, leading to higher frictional losses. It turned out, the difference between the compressor discharge pressure (work) and the intake plenum pressure (downstream) was nearly 6 psi! This at a plenum requirement of 32 psi. On the diesel this is around 60-65 lb/min of airflow.

Now hopefully I have not lost you. The plumbing restrictions when considering the 2.5" IC plumbing and the IC itself, totalled 6 psi. (2.5" is way too small)

After working through the compressible flow equations in a 2.5" conduit, it turns out the increased discharge temp was creating much of this loss, via increased air flow velocity. With fluid flow, there is apoint where the force required to push the fluid (air) through the straw (or IC pipe) becomes exponential, the curve quickly rising vertically at some flow rate. When this happens it is time for a diameter increase from the engineers. (what in fact happened, is that GM reduced the diameter from 3.0" in previous models, and to this day there is no known explanation why)

Adding insult to injury, that high temp product was leading to dramatic ambient temp increases behind the grill. The IC sits in front of the radiator, and measured ambient in front of the radiator, on the hot side of the IC, was 240 degrees! So the CAC was acting like a torch to heat coolant. I calculated something like 290,000 BTU/hr of heat exchange with the IC. Nuts!

But back to hot discharge product. The predictions for this non-adiabatic behavior, show that velocity increases dramatically, and adds a lot of added restriction in the plumbing. Clearly cooling the charge increases density, reduces velocity, and hence pressure losses. This means that, for a given desired intake plenum boost pressure, less work (discharge pressure) is required. This compressor now works less, which means higher efficiency. The improvement is cyclical in nature.

it appears that pre-compressor WI, PCWI, can be a performer or a deterent to performance. If you already operate in the efficient islands, on a humid day, then cooling charge can move you to lower efficiency on the left. It also leads to huge condensation effect in the IC. So PCWI would have limited usefulness on a properly designed forced induction platform with large stock amounts of charge cooling. But the undersized compressor, operating on a dry day, with excessive air box temps, should benefit big.

From my point of view, I do not share the idealized concept that WI provides quasi-isothermal compression. I believe that all the inefficiencies of non-adiabatic compression are in place even with WI. But naturally the beneficial impact of cooler charge can be seen in my explanation. But I don't believe that WI improves the efficiency of the compressor, from a purist sense. This assumes that there is no appreciable evaporation prior to compressor, as is the case in an axial mount nozzle in front of the nut.

Richard, I have tried PM'ing you and email. What am I doing wrong?

What happened? Did everyone die? Or is it just cold everywhere but here?

I think theys did :D

Still trying pre-compressor injection... but nothing conclusive yet. BY lowering the onset pressure from 10 to 8psi on my 1.9TD diesel, I was fairly sure that a small effect was noticeable (0.3mm jet, not a lot of water) but then other things conspired against my tests

Have bought some temperature instrumentation to see if I can detect a reduction in charge temp after the compressor, or rather, how significant it is

Harry, I am interested in your results. I have done some post compressor temp and pressure monitoring, but not with WI yet. I did it in conjunction with evaluating larger boost tubes. Used a nifty 4-channel temp datalogger.

If you have a VGT, and if it is like others I have seen, the WI should lower discharge pressure, while maintaining equal plenum pressure. Curious if you find this to be true. The effect should be magnified in systems with a lot of pressure drop, high IAT, and high boost/low efficiency/off map operation.

Anyway, all this means that for a given boost, is less wok that turbo must perform, and lower final charge temps, better charge density, hence better economy. For those that tow, and have a thermo-viscous fan, the fan can be kept off with lower CAC heat rejection, and this can be a huge benefit.

That's the theory anyway.

VGT?

That's me running a small A/R turbo that starts spinning early but soon reaches the turbine limit and probably chokes the compressor too.. hence high EGTs, and haven't been able to see any definite EGt eduction yet, but no doubt there must be some...

Going to look at my compressor vanes today, pretty well requires removing turbo... alos have had turbine/CHRA gas leaks (kKK's are bad for sealing that joint)

Where did the EGT reductions come into play?
I've yet to find a documented case of EGT reduction anywhere in the (sparse) literature.

EGTs not increasing at even higher boost -- yes
EGTs decreasing ---> haven't seen that yet.

Well, true, I had been told not to expect EGT reductions of signifance, however, on a digital EGT a friend with same engine is seeing at least 30C reduction with post turbo Water Injection.

Mine are so high, that I thought I might see something of benefit in that area...

Non-intercooled 1.9 TD diesel, 12~15 psi boost