Aquamist jet location ????

[lui]

Just wondered where's the best place to fit the jet for the Aquamist set up.

Also have Blitz LM V spec 4 row front mounted inter-cooler & hard pipes fitted.

[Gamer]

Just before the throttle body.

 

You can see here where mine was placed. It is the white tubing going to the brass fitting just before my throttle body.

 

[uk-rich]

i spoke to the guy who own's ERL about this, he says as near to the outlet of the intercooler as possible, he was very insistant on this

 

HTH

[Burna]

i spoke to the guy who own's ERL about this, he says as near to the outlet of the intercooler as possible, he was very insistant on this

 

HTH

 

Would that be the same case for a SMIC too Rich? Seems a long way from the throttle body then.

[uk-rich]

he said it was to give the water/vapour the maximum time to atomise/mix or something, i have a pint or two since then

 

i mentioned about a few cars that i have seen with it very near to the throttle, he said that was a no-no

[Chris Wilson]

When I had my MKIV I tried several different locations for the jet, accurately measuring intake air temps in the plenum. I found I consistently got the best results with the jet near the throttle body, with it near the outlet of a stock I/C I actually saw little gain... I am sure Richard Lamb has good reason to cite the placement where he does, but I had to follow the gauge, not the guru, in this case

[uk-rich]

in that case i'd put it wherte chris says, he has done the research, i was only quoting what i was told

[Gamer]

For most installations the water injection nozzle(s) should be place immediately after the intercooler, if one is installed. Unfortunately, there is no formula for where the best location should be. If you have no intercooler, the nozzles should be placed as far from the throttle body as practical. This give the water more time to change state from a liquid to a gas. This state change is what removes a large amount of heat. The same is true if you have a particularly inefficient intercooler. Having said all that, there is a large benefit to having water in liquid form reach the combustion chamber as it will substantially reduce the combustion temperature and hence slow the combustion process and the tendency to knock.

 

Above was taken from another site. Not sure if the Aquamist system is different from the Cooling Mist system (apart from the obvious pump differences) most of the stuff I have read just say placement somewhere between the intercooler and the throttlebody. Also not sure if this is taking into account that you might or might not be running something other than water alone (Water/alcohol mix). As Chris states though most literature that I read says that you should experiment with nozzle placement for the best results.

[Tricky-Ricky]

When I had my MKIV I tried several different locations for the jet, accurately measuring intake air temps in the plenum. I found I consistently got the best results with the jet near the throttle body, with it near the outlet of a stock I/C I actually saw little gain... I am sure Richard Lamb has good reason to cite the placement where he does, but I had to follow the gauge, not the guru, in this case

 

Where abouts did you measure the temps in the plenum Chris? did you check around the no 5 and 6 intake runner end?

[Chris Wilson]

Tricky: Yes, I put a probe in the plenum at the back. The WRC cars, when running WI, used a mega expensive Bosch pump, and individual water injection nozzles firing onto the backs of the intake valves. So there appears to be several differing opinions on this!

[Wez]

How about this for a thought.

 

The further away from the throttle the more time it has to take heat from the inlet air, BUT the heat is still there, its now moved to the water.

 

Maybe this is why it works better closer to the throttle as it doesnt have enough time exchange the heat and the waters cooling properties works more efficiently in the combustion process.

 

Maybe, dunno, just a thought

[Tricky-Ricky]

Tricky: Yes, I put a probe in the plenum at the back. The WRC cars, when running WI, used a mega expensive Bosch pump, and individual water injection nozzles firing onto the backs of the intake valves. So there appears to be several differing opinions on this!

 

Hmm interesting, especially your test results, not doubting them, but may have to start swapping my thermocouples about;) i know there are a lot of opinions/theory's about jet placement, i have spoken to Richard at length about this and know he always advocates just after IC for jet placement, however i do believe that there are a lot of variables involved, and after hearing you results, i am starting to wonder if the Supras very long std IC pipework runs is the cause? thats presuming you where using STD IC placement?

[Tricky-Ricky]

How about this for a thought.

 

The further away from the throttle the more time it has to take heat from the inlet air, BUT the heat is still there, its now moved to the water.

 

Maybe this is why it works better closer to the throttle as it doesn't have enough time exchange the heat and the waters cooling properties works more efficiently in the combustion process.

 

Maybe, dunno, just a thought

 

Like the idea, but WI is based on waters ability to channel latent heat, ie it can cool/absorb heat without it being a carrier, the theory goes that the finer the droplet size, ie mist, the more surface area there is to absorb heat, water can absorb a lot of heat without its temperature rising in proportion, so if you have large droplets of water they cannot absorb as much heat, there is a lot of technicality to the process but its essayer this way + i can't remember most of it;)

[Wez]

So the heat is still there its just transfered from the air to water?

[Tricky-Ricky]

So the heat is still there its just transfered from the air to water?

 

No! a large part of the water mist has evaporated thereby reducing the temperature.

[Wez]

Ok.

[lui]

Wez mate any chance of a close up pic of where your jet is placed on the throttle body ???

[Wez]

Here you go.

 

[lui]

Here you go.

 

http://www.zen85016.zen.co.uk/gallery/odds/IMG_2395-s.JPG

 

Cheers Wez

 

So is this the best location then to fit jet ???

[Wez]

It was installed by CW, his testing showed this was the better location on the 2JZ-GTE.

[Tricky-Ricky]

Had a little chat with Richard Lamb about this, and this is his response, i am sure he will have no problem with me reproducing this,

 

"Water normally exists in the form of liquid (as in puddle) or in vapour (humid air). Anything between the two states is termed as suspended droplet. The size of the droplet is proportional to the surrounding temperature and pressure. You will notice this when driving in the early hour of the morning through and series of foggy areas. Area where the sun heat has shone through is normally clear of fog. It doesn't mean the the droplets has turn into single molecules, it just become smaller and one can see through it (no fog).

 

If you apply the same physical property of water vapour in water injection application, it should behave the same way. Water is converted into small droplets via an atomising nozzle for the sole purpose of increasing the surface area. If water is used for effective induction cooling, the nozzle should logically be placed as far away from the throttle as possible, allowing ample time for the hot air exiting the IC to mix with the water droplet. During its journey, as the heat is being absorbed, the droplet size is reduced. Please note that there is never enough heat energy to reduce the water droplet size to a single molecule. At best the drop might reduce from 80 um to 60 micron. Each micron-droplet still contains thousands of molecule of water, the occupation of air volume is minimal.

 

A relatively minor reduction in droplet size will absorb a great deal of heat in the inlet track. The amount of vaporisation will depend on the temperature, pressure and wetness of the incoming air. When the 100% relative humidity is reached, no more vaopour is formed. The droplet continues its journey pass the throttle and into each inlet runner. If the droplet is small, there is a good chance of better droplet distribution amongst the cylinders. Most engines are tuned to the knock threshold, if the droplet is not evenly distributed, one will tune the engine based on the cylinder receiving the least amount of cooling. The other cylinders are over cooled and loose combustion temperature and pressure - simply put, power is lost unnecessarily.

 

Ford's WRC WI system has gone through many tests on jet placement and ended up at the exit of the IC. The Subaru started at the throttle placement in later changed to the exit of the IC. I can give example of other WRC teams with post IC jet placement. There is a simple experiment you can do, put you hand on post IC tube after inject, it is almost cold to touch. Temperature probes can give false readings if the sensing tip is wetted and then evaporated. We have recently has a feedback from a 8-sec-quarter-miler running two 1mm jets after the IC, datalog shown high inlet temperature but the pipe was "very cold" to touch, immediately after a run. He will soon change the sensor probe to a open tip thermalcouple type rather the slow responding thermistor type.

 

Ideally, you should a jet per port and one jet at the exit of the intercooler to maximise your water injection effect, both in-cylinder and inlet tract cooling. This is only my view, and not gospel."

 

 

 

 

Interesting observation about temperature probes giving false or unreliable reading when wet and rapidly cooled, a factor that i had overlooked, and my well have resulted in your lower readings Chris.

[JohnA]

There is some confusion here regarding the expected function of WI.

 

1. If general chargecooling is the main aim (say your post-IC temps are too high), then you want to maximise the distance between the jet and the cylinders.

 

2. If chargecooling is the main aim because your IC is totally overwhelmed and heatsoaked then injecting *before* the IC would be an option.

 

3. If in-cylinder cooling is the main aim (your post-IC temps are not far from ambient at full boost but you still get knock) then you want the jet(s) as close to the cylinders as possible

 

4. If a combination of effects is the aim, then you may have to mix and match jet locations, probably making trade-offs.

 

There are also more advanced jet options. It really depends on what the aims of the particular installation are.

[Wez]

There is some confusion here regarding the expected function of WI.

 

1. If general chargecooling is the main aim (say your post-IC temps are too high), then you want to maximise the distance between the jet and the cylinders.

 

2. If chargecooling is the main aim because your IC is totally overwhelmed and heatsoaked then injecting *before* the IC would be an option.

 

3. If in-cylinder cooling is the main aim (your post-IC temps are not far from ambient at full boost but you still get knock) then you want the jet(s) as close to the cylinders as possible

 

4. If a combination of effects is the aim, then you may have to mix and match jet locations, probably making trade-offs.

 

There are also more advanced jet options. It really depends on what the aims of the particular installation are.

 

Great post, just the info I was looking for.

 

 

So if I wanted to inject using a max 0.9mm jet would a better solution be to have a 0.5mm near the IC and 0.4mm infront of the throttle therefore getting the best of both solutions?

 

[JohnA]

#1 The further away a jet is from the cylinders, the more compromised the mist distribution gets. You get a tad more temp drop at the expense of in-cylinder cooling.

 

#2 The bigger the jet, the worse the atomisation (less fine mist) and the worse the heat-exchange or cylinder distribution (large droplets don't take turns easily)

 

#3 The more water you inject, the worse the intercooling effect and the better the in-cylinder cooling

 

#4 The more methanol you inject, the better the intercooling effect at the expense of in-cylinder cooling (opposite of #3)

 

 

The larger picture: water is very good at absorbing heat inside the cylinders (FOUR times as good as excess fuel in fact) but not as good at cooling the charge, especially if the post-IC temps are already low.

 

So if your post-IC temps are 100+C at full boost, then WI will be quite good at lowering them.

But if they are 40C on a 30C day then you will only see a marginal change (if that)

 

But if your are hovering around knock conditions and there is water mist in the cylinders you will not get any knock.

That is what WI is really good at, not further dropping charge temps after a FMIC.

 

So if there is a single sensor that would demonstrate the effects of a good WI installation that would be a knock sensor not a charge temp sensor.

[Stevie Boy]

Feel like i'm gonna open a can of worms here, but what are your opinions on pre-turbo jet location, providing the jet atomisation is small enough not to cause damage to the compressor, would this not improve the efficiency of the turbo. ie. Widening the efficiency island of the of the turbo charger map by providing a denser air supply to compress at high boost?

 

IIRC a degree of heat is required to commence the air compression, but having WI added as boost level becomes high can as such extend the efficiency map of a particular turbo.

 

Would this pre-turbo location be useful on stock TT set-up where EGT's can soar when trying to run high boost level's where perhaps this would not be as necessary on single turbo arrangements with freer flowing exhaust/manifold arrangement?