i dont know if this is correct but i also came up with 1.83 hp using a lazier method
an online calculator at
On-Line Fan Calculation
under FAN APPLICATION FORMULAS
to figure Fan Brake Horsepower
Flowrate (CFM): i entered 70 -roughly 2000liters per minute
Static Pressure at Discharge (in. Water): i entered 166 -roughly 6psi
Static Fan Efficiency (%): i entered 100
and it spit out 1.83hp
but that 1.83 hp on the table is why people can see gains with hot air intakes