Heat Load to the Cooling System
The heat load to the cooling system is related to the flow through the radiator and the temperature drop through the radiator by the following expression:
Q = M * cp *dT
Where Q is the heat load BTU/min., M is the mass flow rate of the coolant in BTU per pound per degree F, dT is the temperature drop through the radiator in degrees F, and * indicates multiplication. Since a gallon of coolant weighs about 8.3 pounds, we can replace M in the expression by 8.3 times the coolant flow in gallons per minute, or GPM.  The resulting expression is as follows:
Q  =  8.3 * GPM * cp * dT
Since the specific heat of the coolant is essentially constant and the coolant flow rate is constant at rated engine speed, the expression tells us something that surprises most people. That is, for a given heat load and coolant flow rate, the coolant temperature drop through the radiator will be constant, and nothing anyone can do to the design of the radiator can change that. Adding rows or fins or face area or whatever will not change the temperature drop through the radiator.  As a general rule, MX cooling systems are designed to operate with a coolant temperature of about 190 degrees F at the radiator inlet and have about a 10 degree F temperature drop through the radiator at rated power and rated coolant flow.  This will result in a outlet tank temperature of 180 degrees F.
Note that the coolant temperature drop through the radiator must be specified in degrees F or degrees C, not percent.  Taking a percentage of the radiator inlet temperature will yield different results depending on whether the inlet temperature is given in degrees F or degrees C.