For most pollsters, the evangelical vote is those who are self-described, black or white. Some may differentiate black and white evangelicals, but I haven’t looked for them.
Seems to me that black evangelicals who would vote Republican might favor Trump.
So, the incessant talk of Ted Cruz's appeal to evangelicals in Iowa, and now SC, means that a lot of black voters are a part of the evangelical group he appeals to?
I've never seen a political discussion where black evangelicals were discussed as being separate from the general black voter group. In fact, black evangelicals probably make up half or more of the black vote.