Both sides were missing several players ahead of the Six Nations but it was Ulster who made a fast start in Belfast.
Murphy’s side were camped in the Cardiff 22 and got the reward for their early pressure.
Prop Wilson crashed over under the posts in the 12th minute after some good work by David McCann to charge into the 22, and Jack Murphy added the conversion.
Not to be outdone, Australian prop Bell, who is on a deal with Ulster until the end of the season from the Waratahs, scored the try of the night in the 19th minute when he picked the ball on the 22, broke through two tackles, sat down Winnett with a superb sidestep and raced over the line.
Murphy again added the extras, and Bell’s try was so good it left Ulster back row Marcus Rea with his hands on his head, in disbelief in what he had just seen.
Cardiff, who overturned a 14-point deficit with 15 minutes left in December’s Challenge Cup game in Wales, responded well and almost got over through prop Rhys Barrett after a tap-and-go, but Wilson got under the ball to stop it from being grounded.
The visitors threatened eight minutes after the restart when hooker Evan Lloyd made several metres, but the in-form Zac Ward, who missed out on Ireland selection, claimed Callum Sheedy’s kick under pressure and the chance was lost.
But they made their pressure count in the 54th minute when the forward hammered the Ulster line and scrum-half Yohan Mulder raced over the line.
The stop-start nature of the game did not help either side as temperatures fell and the rain increased, and replacement Dave Shanahan somehow dropped the ball with the try-line gaping from Matthew Dalton’s offload.
Ulster got their third try moments later when Irvine, a part-time medical student, powered over the line, which Murphy converted, but Cardiff immediately responded when Emmanuel latched onto Sheedy’s pass and raced clear, and the fly-half converted.
Cardiff threw phase after phase at the Ulster line, but James Hume produced a big turnover with five minutes remaining.
Ulster then went up the other end and were held up over the line, but the win not only moves them up the table but preserves their unbeaten home record this season.