With both teams still to settle qualification for the quarter finals, it was Coventry who took the lead as Jordan Pietrus opened the scoring after six minutes.
Joey Martin levelled things up to tie the first period at one apiece, but the action really took off in the second period.
Paul Crowder put the Devils in front before seeing his goal cancelled out by David Clements as the tense cup tie was being played out.
But suddenly four goals in the space of five minutes turned the game in Cardiff’s favour and Coventry’s fate in the Challenge Cup was sealed.
Andrew Hotham restored the home side’s slender advantage, followed by strikes from Gleason Fournier, Jake Morrissette and a second from Martin saw them 6-2 ahead.
Another marker from Layne Ulmer early in the third confirmed victory on the night and the prospect of a quarter final tie to come for the current champions.