A blacksmith's coal fire will be about 3000 F. Increasing the volume of air increases the amount of "HEAT" but not the temperature. The OAW _neutral_ flame is about 6000 F. Increasing the tip orifice size increases the amount of "HEAT" but not the temperature.
In the electric arc welding processes there are three electrical variables to enable or produce the electric arc necessary for welding. They are: volts, amps and resistance. The Volts affects the height and the width of the weld deposit. The Amps has the greatest affect on the depth of penetration. Electrical Resistance to the flow of amps/current through the arc (air/gas gap) produces the HEAT to melt the metal. An electrical arc welding machine has one _MAIN_ electrical variable control. That main control will increase/decrease voltage or amperage. A machine that has a voltage adjustment is called a constant voltage/variable amperage machine. A machine that has an amperage adjustment is called a constant current/amperage/variable voltagemachine.
Heat Input is Volts X Amps X 60 divided by the travel speed. To increase the "HEAT" Input would therefore mean/require the increase of one/both of the electrical variables (volts/amps) or decrease the travel speed.
Increase in desired penetration requires additional amperage. Decrease in desired weld bead height and increase in weld bead width requires additional voltage. That is the travel speed remains unchanged.
A good test is worth a thousand opinons.