Time: 3:45s for Indian teas, and 4:15s for chinese blacks
Ratio: 1g leaf : 90g H20
Temp (measured in vessel): ~190-195F (88-93C) for FF and SF Darjeeling. ~205F (96+) for fully oxidized blacks. (measured after pour into preheated vessel)
So I preheat and set my perfectemp kettle to 200F for FF Darjeeling, and boiling for others. I used to be hesitant to brew expensive blacks at boiling, but one of Hojo's blog posts, Why do we rinse tea, encouraged me to do so:
The flavor and taste of fermented tea such as oolong and black tea are composed of substances like terpene and conjugated poly phenol. These substances are produced as a result of enzymatic oxidation. These substances have lesser affinity than poly phenol exists in non-fermented tea like green tea. Hence, it is important to get higher temperature to efficiently extract the substances when brewing fermented tea.