How long after taking 16 mgs of suboxone can you feel opiates?

I would say you would need to firstly wait until withdrawal effects have started (if you are addicted to opiates), or you need to wait until the opiate is "out of your system" (if you simply use opiates recreationally and are not addicted). If you take Suboxone whilst under the influence of opiates (ie, heroin, methadone...etc) then you will encounter what's called "precipitated withdrawals". This is particularly nasty, and feels much, much worse than the usual withdrawal symptoms.

Although I allude to the opiate being "out of your system" above, that does not necessarily mean it need to be completely out of your bloodstream... to put it simply, you just need to make sure you are no longer under the influence of opiates. For example, if you take heroin on a Monday, it will still be in your system by the Thursday, but you would be ok to take the suboxone on the Tuesday as you wouldn't be drug induced by then. (NB; the previous example will not apply to methadone, which has a much larger half-life and can keep you drug induced for nearly 48hours).

Basically just use your judgment - only use the suboxone when you feel sober