Question for Aquamist and water pressure selection

[mx5]

I am looking at the flow numbers listed for the jets at the Aquamist site:

http://www.aquamist.co.uk/sl/plist/pic2/jets/jets.html

Let's pick up the 0.5 mm jet. The link above says it flows:


150 cc/min at 72.5 psi (5 bar) ( with the standard pump )
200 cc/min at 101 psi (7 bar) ( with the race pump )

I have the Aquamist 2D kit. I haven't attached a water pressure gauge, but the water pressure sensor had writing on the sticker that it is preset to 75 psi. Why is that?
The higher the pressure the better the water will be atomized, right? The Aquamist 2D includes the race pump. Then why is the kit set from Aquamist to keep the pressure at 75 psi since everywhere else at the site the quoted flows with the race pump are at 100psi?

Should I get a water pressure gauge and readjust the sensor to 100psi? Or to some other value? Or was it set at 75 psi from Aquamist because some damage in the 2D kit might occure at higher pressures? I want to be running the system as effective as possible.

If this info is needed - Currently I am running 0.4mm jet (but I will go to about 0.6mm soon). In addition to the standard 2D system I have a 40cc accumulator installed, and a check valve after the manifod/water pressure sensor (the check valve is between pump/manifold/water pressure sensor and accumulator/HSV/jet)

[Charged Performance]

Can't speak to all the reasons for the approximate setting.

However you will notice that the jet flows for are also listed there for 5 bars. A great benefit of the pressure switch is to permit another adjustment to water flow rather than the step jump of jet switching.

There would be nothing wrong with running the 2d at 7 bars.

Out of curiosity why the use of a check valve and why that particular location? The hsv would act as check valve when it is not opened.

Your best bet is at the current setting measure the max flow through your jet(2) by grounding the brown wire from the hsv while the car is in the on position (not running) and the jets are in a measuring container for one minute. Choose a jet or jet combination close to what you are looking to get maximum flow wise using this method. From there you can adjust the pressure to get exactly the flow you are seeking.

With regards to atomization and pressure. The aquamist jets will atomize properly with at least a 2 bar difference across the face of the jet. Any incremental atomization benefit from a greater difference would not be as noticeable as the ability to control the flow rate. (i.e. being at only 100 psi is not so much better atomization that it is worth not being able to adjust the flow up or down)

[mx5]

Can't speak to all the reasons for the approximate setting.

However you will notice that the jet flows for are also listed there for 5 bars. A great benefit of the pressure switch is to permit another adjustment to water flow rather than the step jump of jet switching.

There would be nothing wrong with running the 2d at 7 bars.

Out of curiosity why the use of a check valve and why that particular location? The hsv would act as check valve when it is not opened.


I was told here in the forum sometime ago, that the best setup will be accumulator and a check valve after the pump and manifold/pressure switch. I've never tried without it - but Brad said that from his experience it seems to make things better - I just followed the instructions. Check this thread:

http://waterinjection.info/phpBB2/viewtopic.php?t=88
and especially this post from Brad:
"Mounting the pump and pressure switch in the trunk poses very few problems. If you add a 806-249 check valve after the pressure switch and an good sized accumulator up front the system will be very stable. I would use on large accumulator for each 200hp for maximum protection. The accumulator I use is not from Aquamist, it is about the size and shape of a soft ball. It can be "T"ed into the line with and 806-360 or 806-361. The check valve after the 806-201 manifold is not required it just seems to make things work better. The check valve eliminates the effect of flex in the long line to the front. Again the check valve is not required but experiance has proven it works better. If it helps I have been involved in more than 20 setups like this and and learned from each one of them."

Your best bet is at the current setting measure the max flow through your jet(2) by grounding the brown wire from the hsv while the car is in the on position (not running) and the jets are in a measuring container for one minute. Choose a jet or jet combination close to what you are looking to get maximum flow wise using this method. From there you can adjust the pressure to get exactly the flow you are seeking.

With regards to atomization and pressure. The aquamist jets will atomize properly with at least a 2 bar difference across the face of the jet. Any incremental atomization benefit from a greater difference would not be as noticeable as the ability to control the flow rate. (i.e. being at only 100 psi is not so much better atomization that it is worth not being able to adjust the flow up or down)

I did some experiments few days ago with running the 2D at low IDC. And when the pulses are short, there is no mist coming out of the jets, but stream - this was even with the 0.4mm jet.
So at low IDC - the system is not capable to make mist, but just fills the intake manifold of the car with water - it was confirmed by Richard L.
If I try that with a bigger jet it will be even worse.
So my idea was upping the water pressure will atomise the water better and the mist will be finer (during low IDC) if I use smaller jet/higher pressure than bigger jet/standard preset pressure.
What is your experince with this?

[Charged Performance]

I recollect now your set up with the pump back there yes it does work well that way.

That would make sense the longer the hose after the HSV that a low cycle would never actually build up the correct pressure at the jet with a low IDC. I think you will find that the closer the hsv (with pre stored pressure behind it) is the jet it will atomize better at lower IDCs than if the hsv were further away.

[mx5]

I recollect now your set up with the pump back there yes it does work well that way.

That would make sense the longer the hose after the HSV that a low cycle would never actually build up the correct pressure at the jet with a low IDC. I think you will find that the closer the hsv (with pre stored pressure behind it) is the jet it will atomize better at lower IDCs than if the hsv were further away.

It is not the HSV to jet distance. The HSV is mounted about only 4 inches away from the jet.
Then the 40cc accumulator is mounted 3-4 feet behind them and everything else (check valve, manifold, water pressure switch, pump) is feet away back in the trunk of the car right next to the battery.

The setup was same exact one during the low IDC test too.
So the HSV was right next to the jet with pre-stored pressure (accumulator too) - the pressure was whatever the 2D does at stock settings - currently I don't have a gauge to monitor it.

So back to the pressure now :) Do you think upping the 2D pressure switch setting to 100 psi will help? Or is any other value suggested? What is the max before things start breaking? And why was it set at 75 from the factory ( hey, Richard L ? )

What pressure gauge should I get? Does the Aquamist one which uses a 4mm line in a tee work fine? Do I have to take the air out of the line to the gauge, or just tap it in the tee and not to worry?

[Charged Performance]

OK I see - this is not as I would have expected. I would have thought with a short volume to fill up between the hsv and the jet that it would atomize on low IDCs. How low are the IDCs we are talking about? I guess one issue is I have never seen a pulled jet engaged at less than 25% IDCs.

Try it with more pressure and see how it works then. I still think it is a function of how quickly and how much flow fills the volume between the hsv and the jet. The smaller the volume or the more quickly the volume can be filled the lower the IDC should be able to be and still atomize.

[Brad]

The nozzle needs at least 50% of it volume rate to spray. It can not spray at 10% rated volume.
The Aquamist nozzle is a flow nozzle not like a fuel injector nozzle. It requires flow to spray. A fuel injector sprays because the opening is very short to control flow.

[Charged Performance]

So back to the pressure now :) Do you think upping the 2D pressure switch setting to 100 psi will help? Or is any other value suggested? What is the max before things start breaking? And why was it set at 75 from the factory ( hey, Richard L ? )

What pressure gauge should I get? Does the Aquamist one which uses a 4mm line in a tee work fine? Do I have to take the air out of the line to the gauge, or just tap it in the tee and not to worry?

The Aquamist one includes a 4mm line. I generally have not bled air out of fluid pressure sensor lines. Another alternitive is to use the manifold block which has a 1/8 BSP thread I believe. If needed E-gauges has an adaptor from 1/8 BSP to most American fluid pressure gauges which use 1/8 NPT.

I would not seek to get more than 100psi from the pump. However, brad has much more experience with these systems than I do - their atomization appears dependent on flow first - then most likely the 2 bar differential. So you may have no alternative but to not rely on water injection for tuning at lower IDCs - though theorectically with 100psi you would have more flow while open than at 75psi. Again though I am sure brad would mention if there was a way to get atomization from lower IDCs and he has indicated that there isn't.

[Richard L]

Mx5,

Thank for reminding me of this thread, I somehow missed it. I check the sponsors section everyday and may be you can post it to that section in the future if things get urgent.

We normally set the pressure switch between 6-7bar but only stated 5 bar for the following reasons:

1) Voltage drop along a long cable or bad chasis earth will affect the peak pressure if the pump is not connected to the battery directly.
2) The rated pressure is guaranteed up to the largest jet of 1mm.
3) We rather understate due to the reasons given above.

In your case you can increase the pressure to a maximum of 9.5bar. The pump will maintain these pressures up to a 0.6mm jet and 0.7mm at 8 bar (under the ideal conditions). If you don't have a pressure gauge, you can base on 1/4T clockwise will increase the pressure by 0.5bar or 1T=2bar.

With the 2d, you can be pretty generous with the jet size as it is progressive with your fuel injectors' Duty cycle.

[Richard L]

In order to get a reasonable injection pattern at low flow, you need to fix the jet directly onto the HSV with zero cavity between.

We have this set up at every show and the spray was very resonable even at 35% DC. (0.7mm jet) pressure was set at 8 bar.

See images below:


http://www.aquamist.co.uk/forum/35.JPG http://www.aquamist.co.uk/forum/85.JPG

[Charged Performance]

Richard, thanks for the response. This is what I was expecting that any volume between the hsv and the jet would affect how short a duty cycle could be and still achieve atomization.

[mx5]

How do I attach the jet directly to the HSV? Do I need any extra hardware which is not included in the 2D?

Also for the other end of the HSV where the 4mm tube will go in, is there a replacement L shaped fitting (90 degree angle). The HSV with the fittings is a bit long now, so if I attach the jet on one side it would be great if I can make the 4mm tube go in at 90 degree angle.

[Richard L]

MX5,

It is not that easy, the picture just shows you the difference of zero cavity's effect.

I think if you can keep the line short, it will help. It is only critical when the rate IDC is below 20%.

[mx5]

What's not easy? To attach the jet directly to the HSV? Isn't there some kind of fitting?

[Richard L]

Is not the fitting that is difficult, but the strength of the material on the jet will not be able to support the weight of the HSV under constant vibration from the engine.