Select time attack either Single or Tag. These can be done with just one round 
for the win:

Code - Effect
------------------------------------------------
Finish single in 5:00 to 6:00 - Bronze (Single)
Finish tag in 4:00 to 4:30 - Bronze (Tag)
Finish single in less than 4:30 - Gold (Single)
Finish tag in less than 3:30 - Gold (Tag)
Finish single in 4:30 to 5:00 - Silver (Single)
Finish tag in 3:30 to 4:00 - Silver (Tag)