unconsciousness: hits between 5-30 minutes post-ingestion for most successes. hard to predict. Everybody reacts differently, so calculating the most effective dose is hard. 250-350mg SN per 1 kg body weight is the usual.
death: 10 min to 3+ hours if it works. plan a lot of time before being found
In general, hope for Benzos to knock you out before SN does