Extremely confused by calibrating lawn sprayer

[Dcf1999]

I'm really confused on calculating what my sprayer spays per acre (GPA). I read through numerous instructions and my calculations all add up, but then I look in my manual and it gives me different numbers. Here are the specs:

GPM per tip: .5 gal and I have 2 tips on my boom so total boom output is 1gpm
Tractor speed is 3 mph
tip spacing is 40" and it sprays a 80" swath.
Spray pressure: 30psi
Make model or rig: Master Manufacturing (from Big R) model number: SNO-11-025A-MM

Through the calculations, I came up with my rig spraying 24.74 gallons per acre (or .468 gallons per 1000 sq ft)
I look in the manual and it says that the rig will spray @30psi (with gray tips producing .52 gpm) 22.3 GPA at 4mph. They don't have a column for 3 MPH so interpolating from the cart, at 3mph it's about 24.5 GPA. So it seems to add up that my calculations are correct! yay! but in the footnote it says that the 24.5 is PER NOZZLE... since I have 2 nozzles (producing .5 gpm each) that comes to 49 gallons per acre?????

So where is the manual coming up with 49 GPA when my calculations are 24.75 GPA?

Way long ago I think i figured this out in my head but i can't remember now. Maybe the manual is wrong?

I'm spraying a chemical that needs an application volume of 1 gallon per 1000 sq feet. using the manuals 49 gallons per acre, that can be done. But if I use my answer of 24.75 GPA, i only have an application rate of .56 gallons per 1000 sq feet. Which means i will need more chemical.

Anyways, can someone help me figure this out.

 

[Foodplot]

Put water in the tank, hang a bucket on each nozzle and see what volume you really get. Then adjust your speed or concentration of your solution to get your desired application rate.

 

[CobyRupert]

tip spacing is 40" and it sprays a 80" swath.

Can you explain more about this?
Does this mean each nozzle sprays 20" to each side?

With 1 gpm total spraying discharge (2 tips), over the course of 1 minute you've sprayed 1 gallon, on a 6.66' (80")wide area and traveled (at 3 mph) 264 ft forwards.
That's 1 gallon on (6.66' x 264') 1760 square feet over 1 minute.

1 acre =43560.17 sq. feet, so spraying at 1760 sq.ft/min, means it takes 24.75 minutes to do an acre. And at your 1 gpm spray rate that's also 24.75 gallons on 1 acre (24.75GPA).

Something is off by a factor of 2.
Either your nozzle gpm, their nozzle gpm, number of nozzles, or nozzle arrangement (i.e. 2 nozzle can either double the coverage area (if not overlapping) or double the concentration (if both are spraying the same area)).