Advice on setting up a Aquamist 2c

[eunos1800]

Hi Guys,

I will shortly be fitting a Aquamist 2c to my 1994 Miata with MP62 Supercharger running at around 11psi.
I will be running without a IC, and will be running the 2c from my Emanage Ultimate.

Firstly,
I would like some advice on calculating a good starting point for how much water i need to inject.
I can roughly calculate the volume of fuel i'm injecting by subtracting the Injector Duty cycle from the Injector peak flow size.

For example,
My Injectors are 420cc, so if they are at 50% DC that 4x420= 1680cc/per min
At 50% DC this means i'm burning 840cc/per min of fuel.
If i start off at 10% water then does that mean i need to start off injecting 84cc/per min of water?

Of is there another way of calculating it?



Secondly,
Once I've calculated the amount of water i need to inject, how is this represented in regards to what the HSV flows depending on its duty cycle and nozzle size used?
If i use 2 0.7mm nozzles for example, what flow will this give me at say 50% DC or 100% DC?


As you can probably tell I'm new to the WI world, so any advice would be greatly appriciated.



Cheers
Mark

[JohnA]

Several good questions asked here.

A lot depends on the individual engine setup. If the static compression ratio is relatively high then you may want the water injection to start sooner rather than later.

You want it to kick in a bit before the engine starts to feel uncomfortable. Do you have any idea currently of what the inlet temps are under boost? Do you have aggressive ignition settings? (similar to stock?)
If so, you may want to inject a bit more water at max torque revs, when boost reaches a level of a few psi. Do you get any detonation as it is now?
If not, and your AFRs under boost are in the 11s or 12s, then you may want to try injecting at 5psi 10% of water/fuel and see how it feels.

[eunos1800]

Hi John,

The compression ration on my 94 Miata is 9.0:1.
So as far as I'm concerned and please correct me if I'm wrong but that does not seem high to me.

I have not personally measured the intake temps on my car, but from what i have seen posted on the various forums more or less identical setup to mine are running just above 200f.

I am presently at 9psi, usually on Miatas 14btdc is considered to be close to optimal for base timing, i have no idea if this is actual MBT or a guesstimate as i have not personally carried out any dyno testing.

For the sake of argument lets say 14btdc is MBT, at my current 9psi i am at 14btdc but am pulling 4 degrees over peak torque.
At this setting with current ambient temps (10c) i am not seeing any knock.
During the summer months (42c+) i expect it to be a completely different set of circumstances though.

I have not tried the bigger 11psi pulley yet so i have no idea what i will be able to get away with timing wise.
At the current climate i am roughly having to pull 1 degree of timing per 2psi, to successfully avoid knock.
If i use the same formula for my bigger pulley then i will be pulling around 6 degrees.

To be honest John i am not to worried about timing and knock, i have 2 knock gauges running into 3 separate systems so i am fairly confident i will be able to see the onset of knock before major detonation occurs.
Likewise it is extremly easy to adjust the timing with the Emanage Ultimate (EMU).

My main worry is gauging how much water i will be flowing depending on the HSV duty cycle.

To supply 10% water i first need to calculate how much water ib being injectored at various duty cycles and nozzle sizes.


Am i using to correct methid to calculate how much fuel i am flowing, or did i miss something on the search?




Cheers
Mark