sway2003

Hello I am tunning my fd. I have done a base fuel tune to low 11 afr running 14.7psi-15 psi.

My next stage is to adjust the timing and add the water injection. I will be using the new cooling mist vari cool control when i do this. I am running 850cc primaries and secondaries and they are up to or around 80 ish %

i have searched about and it has been suggested to me to re tune to 12.0afr which would be a ruff drop in fuel of 10% and replace with 10% water. I understand that i am just replacing some of the fuel used to cool the combustion and that i am not using the water as fuel. Ie not adjusting the afr with it. So far does this all sound about right.

I am thinking that 10 % water to replace 10% fuel will be to much. approx 2/3 too much. Or am i confusing the units of mass. Some people talk about water injection and use weight to work out there water cooling requirements where as i have used a straight ratio and used gallons as my unit

This is how i have worked out my requirment.
my fuel requirment at 100% idc would be 44gph. so at 85% it would be 37.4gph so if i removed 10% of this fuel and retuned for 12.0afr i would be using approx 33gph of fuel and adding 3.3gph of water at WOT

or do i replace the 10% of fuel i have removed and replace with 3% of water which would be around 1gph of water. The reson for me thinking this is water being a more efficent at cooling than fuel. 3 times more efficent i am told.

I may be completely off track with all of this which is why i have made the write up so long in a attempt to explain what i mean..

otherwise what do other people do/use

SD

RX-Heven

iTrader: (1)

I'm not too familiar with the Cooling Mist system but I believe it is a "dumb" injection system. By dumb, I do not mean bad but that it just injects a given amount of water throughout the rpm/load range. The dual stage system just increases the set amount by another fixed amount but is load dependent when it comes on.

Because of this, the water/fuel ratio/percentage is never constant but diminishes up through the rpm/load so I would be a little nervous about leaning it out too much. Some people run up to 12.5 afr's.

I have an Aquamist 2D system that is dependant upon the fuel injectorduty cycle (idc).
This way, I can target a given water/fuel % and maintain it throughout the rpm/load.

I came up with this awhile back and it seems to work:

To run 15% water to fuel at 70% IDC, I calculate this way:

(IDC) x (Total fuel cc's) x (Target % water) =
(.70) x (1440 +3200) x (0.15) = 448 cc's of water

Then, also assuming the water nozzles operate at 70% DC and one 0.9 mm WI nozzle flows 315cc (max), I get:

(15% water to fuel) / [(WI flow rate) x (IDC)] =
(448) / [(315) x (.70)] = 2

So I would need two 0.9 mm nozzles to meet my 15%.

Note: WI Flow Rate is based upon the Aquamist injector flow chart available fromtheir website.

Also, check out this forum if you have not already:
http://www.aquamist.co.uk/phpBB2/index.php

sway2003

Thanks..I see how the formula works and will give it a go. The vari cool control is differant to the staged system.

try this link
http://www.coolingmist.com/detailmai...pid=controller

sd

pistonsuk

I think Rich Best Torque is ~12.3AFR. This means going richer than this, apart from detonation issues, only reduces your power. It is true that "3x more efficient at cooling". What this really means is the specific heat and latent heat of vaporization of water is ~3x that of gasoline.

One way to figure this out would be to tune with fuel only for no detonation, say 10.5AFR. Then find how much less fuel your engine would require at 12.3AFR. Take this fuel mass flowrate and divide by 3 and this is your water injection flowrate.

I have not done the above mentioned yet, but as far as no hesitation at 15psi I have been injecting about 9gph on my 300whp setup.

Justin

sway2003

I supopse i could finish my current fuel map with safe ignition map and then reduce the fueling to say 12.0:1. Add water untill i see an identical knock or close to that from the richer fuel map. I know this is a dangerous way to tune but talking hyperthetically.

I want to avoid getting bogged down with water and loosing all that i have gained. I was hoping that the controller would give me a bit more flexibility.

What afr did you tune for at 15psi.

SD

pistonsuk

I havent optimized this setup at all...yet. I think I was at 11:1AFR. I was more using it for overkill/insurance. This was last year when I had the car with me at school here in Utah. I was 2000miles from home and only have 91 octane.

I plan to this summer do something like the above mentioned. Tune to 12:1 and add water equivalent to maybe 10.5:1 or so.

Justin

ronbros3

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