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Water Injection, When should it be working


Supra ST Myster

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I would start at 0.8 bar , water injection tends to richen up the AFR depending on what size jet your using, (and a jet of at least .8mm but i would go for .9 or 1.00mm) so after 0.8 bar will help if the fuelling is starting to lean up, also using methanol in high mixes only reduces the effects of water, IE the charge/in cylinder cooling effect, at 50% or over you might just as well just use all Methanol, but then its just an octane additive and not so much a coolant.

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Just installed the coolmist 150psi kit, and was wondering what boost pressure people advise on setting it to squirt water?

0.8 - 1.0bar is a good starting point.

 

But as others have said, it also depends on several other factors.

 

Have you got a picture of the nozzle location?

Also have you measured the flow/min? (just activate the pump with the engine on idle and have it squirt through the nozzle in a calibrated container. This will give you a rough idea)

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Ok, think i will set it up for 1bar, not tested flow rate as of yet, from the looks of it the injector is 1mm. The pump it massive, about 200mm high and 100mm diameter. Got some power as tested it first and the water spray is pretty intense!!

 

 

here is a pic of where the injector is installed.. Thats alright isnt it?

Injector.jpg

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...here is a pic of where the injector is installed.. Thats alright isnt it?

It's OK, but you could do better.

A good location is a few inches closer to the intercooler, right when the 90 degree bend starts. (Imagine the nozzle facing the lower part of the throttle;) )

That way when the air is rushing at 1 bar boost, the water mist is evenly distributed through the throttle. You avoid the 90degree turn that the water dropplets are forced to do as you are currently injecting at the other side of the pipe.

A lot of them will solidify on the wall opposite and you lose the half-decent distribution among the cylinders.

 

Try taking a picture of the nozzle injecting out in the open.

You should only see a hazy cloud. If you can see dropplets it's not good enough.

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The other people are right for best boost cooling you have to mount it as far away as possible from the throttle body.

 

As you have the normal on/off kit I would advise you to start spraying at 0,9Bar. So you wont get much spray in normal day to day traffic but enough in WOT situation where the WI should be done.

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It's not that simple unfortunately.:eyebrows:

 

The further away it is from the throttle, the more time there is for heat exchange.

However, there is more time and opportunities (sharp bends mainly) for the atomisation to lose it's fine status and become lumps of water kicked about. This leads to certain cylinders having less water than others. Not good for det control.

 

This heat exchange also heavily depends on the temp difference between the charge air temp after the i/c and the water temp (usually at engine bay temps). If it is not large enough (30C+ ) don't expect earth-shattering temp drops.

 

Further still, extremely important are the evaporative and surface tension properties of the liquid (hence the various water/meth mixes depending on the needs)

 

So it is a balancing act, much like everything else in engineering.

You need to find the set of compromises that fit your purpose.

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  • 2 years later...
It's not that simple unfortunately.:eyebrows:

 

The further away it is from the throttle, the more time there is for heat exchange.

However, there is more time and opportunities (sharp bends mainly) for the atomisation to lose it's fine status and become lumps of water kicked about. This leads to certain cylinders having less water than others. Not good for det control.

 

This heat exchange also heavily depends on the temp difference between the charge air temp after the i/c and the water temp (usually at engine bay temps). If it is not large enough (30C+ ) don't expect earth-shattering temp drops.

 

Further still, extremely important are the evaporative and surface tension properties of the liquid (hence the various water/meth mixes depending on the needs)

 

So it is a balancing act, much like everything else in engineering.

You need to find the set of compromises that fit your purpose.

 

I am going to get my water injection kit fitted next week along with my CW SMIC. I am running a T61 DBB with an AEM ECU.

 

John's post above has confused me regarding the positioning of the injector, should this be plugged in the throttle body pipe or on the intercooler side?

 

He mentions

 

It's OK, but you could do better.

A good location is a few inches closer to the intercooler, right when the 90 degree bend starts.[/Quote]

 

Where exactly in the engine bay is this, photos would be appreciated?

 

Secondly, Referencing what Wez said here:

 

http://www.mkivsupra.net/vbb/showpost.php?p=1221023&postcount=13

 

Is it possible for the AEM mapped to take into account WI detect a water pump failure in order to switch to a map (without WI)?

 

any help guidance appreciated.

 

imi

Edited by imi (see edit history)
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