I can't give you an exact number as I lost a reference book I used to have on compressed air systems. If you need an exact answer you might try calling a company that specializes in industrial compressed air systems. They have to work out the water weight in the compressed air to design, drying systems so the user does not end up getting wet compressed air at their tools.
I found one reference that gives some ball park values on a chart of lb water in lb air at different temps and pressures.
Airs ability to hold water vapor changes significantly at higher pressures so it is not a simple relationship.
As you can see below as pressure goes up, the amount of water vapor the air can carry at a given temp goes down. Also as the air temp goes down so does the water capacity.
Bottom line if you saturate the air going into the compressor, as it leaves it will be quite dry, while it is still hot, but after being cooled in the CAC it will become super-saturated as the temp approaches the compressor inlet temp. In other words if you had a transparent intercooler you'd probably see a dense fog going through the throttle body.
A secondary conclusion from the above fog formation on cooling just came to me ! The temperature where your charge air becomes supersaturated and forms a water fog will be a hard limit to the minimum temperature the intercooler can reduce the charge air temp to. Once water fog begins to form, the latent heat of condensation of the water vapor released as the charge cools will exactly balance the heat taken out by the intercooler. This is likely the reason pre-compressor injection can appear to reduce the effeciency of the intercooler.
900 CFM would be about 63 lbs / min air flow at 1 atm
From the chart in the Chemicals Engineers handbook (Perry and Chilton)
5th editon, Fig 3-4
Air at:
1 atmosphere and 100 deg F holds 0.04 lb water / lb air
2 atmosphere and 100 deg F holds 0.03 lb water / lb air
3 atmosphere and 100 deg F holds 0.015 lb water / lb air
1 atmosphere and 125 deg F = 0.09 lb water /lb air
2 atmosphere and 125 deg F = 0.045 lb water /lb air
3 atmosphere and 125 deg F = 0.03 lb water /lb air
1 atmosphere and 200 deg F holds > 1 lb water / lb air
2 atmosphere and 200 deg F holds 0.43 lb water / lb air
3 atmoshpere and 200 deg F holds 0.23 lb water / lb air
Assuming your intake air is completely dry:
If you take a small turbo like I have on the WRX which has a max flow of 35 lb / min, and the inlet temp is 100 deg F, and the exit temp from the intercooler is 125 deg F (at 2 bar boost = 3 bar absolute pressure), that 35 lb of air could hold a max of about (.03 x 35) or 1.05 lb or water per minute. That is just over 475 cc/min of liquid water completely evaporated.
If your intercooler is heat soaked, then that same air flow at 200 deg F and 3 bar absolute would hold almost 8 lbs of water per minute or nearly 3654 cc / min of liquid water completely evaporated.
We know that the pre- compressor injection drastically cools the intake charge, so if the inlet air is cooled to 50 deg F by the water evaporation before it hits the compressor, that cool air can only hold a max of about 0.008 lb water / lb of air, or .28 lb of water or 127 cc/min will be able to evaporate before it arrives at the compressor. (that is equal to about .8% of mass air flow).
If the air leaves the compressor at 200 deg F and 3 bar absolute pressure then on exit it could hold a max of 0.23 lb water / lb air. That would equal 8.05 lb water / lb air (3655 cc/min).
If your injecting at 3% of air flow then you injected only 1.05 lb water, so the relative humidity of the air leaving the compressor will be
less than 13%.
Now you cool it down to 125 deg as it goes through the intercooler and you have that same 1.05 lb water but it is traveling in an air stream that is now is only capable of holding about 0.03 lb water / lb air, or 1.05 lb water --- surprise surprise your at 100% humidity as the air leaves the intercooler.
( I didn't plan this to come out at exactly saturation but I'll take the lucky break
)
For your example of 900 CFM you have 63 lbs/min air flow in. If you get 30 psi boost ( 3 bar absolute) and it exits the CAC (intercooler) at 125 deg F then at 100 % RH it could hold 0.03 x 63 = 1.89 lb water / min or 858 cc/min at saturation.
Someone check my numbers but I think that is all correct!
Larry