About 10-15 litres/minuite. If you dont have enough gas you will get a porous weld, also the same can happen if you have to much, especially if your welding intoo a corner.
Apart from that, it wont make hardly any difference.
Big pair of welding gauntlets, one hand holding around the swan neck of the torch shielding the tip from the wind.
Other way is to pull the shroud slightly off the end off the torch so the tip is about 5 - 10mm up inside the shroud.
Can crank the gas up to around 30 l/m without any probs......... just use more of the rather expensive gas!