water and chemical usage in presoak

I am having an issue in my automatic bays with water and chemical usage during the presoak. I have a two stage system; acid (2.4 pH) and base (11.8 pH). Problem is a normal wash (40 seconds) is consuming 10oz of concentrate. The ratio that yields 2.5 pH is 1:128 (one oz per gallon) so I am using 10 gallons of water as well. I have been told by several folks that 3oz of concentrate per car should be enough. Is it really 3X what it should be?
I rebuilt the manifold and replaced eroded needle valves, injectors, and check valves and the system can be adjusted now. If I slowly close the input water valve until the concentrate flow starts to decrease, and then adjust the concentrate flow rate to get 2.5 pH in the bay, then all the adjustments are close to the manufacturer's suggested settings.
The injectors are .083" 2.5-5gpm. Why is it passing 15gpm?? Is it simply the viscosity of the concentrate that requires more pressure (higher water flow rate) from the injector? If that's the case, could I drop down to a .057" 1gpm injector to solve the problem?
The base and acid settings are a little different from each other in that about 6oz of base is consumed. The two automatic bays track each other fairly closely.
Thanks!
WardsCW

Hey George, What brand auto do you have?

Are you marking your chem drums with your car count, or was this through a volumetric test?

Use a titration test on your detergents. PH is measuring hydrogen ion concentration. You want to find out how much STTP ans NAOH etc. are present.

They are Ryko US2001 automatics.

Volumetric. I put the drop tube in a graduated cylindar containing the concentrate and read the difference after running the presoak for 40 seconds. That is my baseline for an average sized vehicle.

My pH reference is from testing the concentrate in solution with my soft water supply. I simply want to approximate that level in my bay, at least that is the goal of the equipment and chemical manufacturer's procedures.
I think I'm good with that, for the moment.

I'm more concerned about the volume and ecomonics of the water and chemicals I'm putting in my pit! From my calculations the drum of concentrate should have lasted several months longer than it did.

I knew I have been consuming too much product but I'm a one man army with several battles going on. I have been in the car wash business since February and bought a business that has sufferred some neglect. I am loving it!