Emmanuel Tshituka was shown a red card for a leading elbow while on a strong charge in the 18th minute, but that didn't deter the men from Joburg, who went on to score seven tries to four for an emphatic win that booked them a place in the quarter-finals against the Glasgow Warriors.
The hosts varied their play well, sometimes going straight up the middle and making ground, and at other times spreading it wide to expose space on the wings. They started like a house on fire and scored two tries in the first seven minutes when Marius Louw and Edwill van der Merwe went over to put the hosts in a 12-0 lead.
The visitors hit back four minutes later with Thomas Moukoro's first try and afer that, some parity was restored until the 18th minute, when Tshituka was shown red, just after Sanele Nohamba had extended their lead to 15-7 with a penalty goal.
However, it was the hosts who scored next when Gianni Lombard put Rabz Maxwane into a gap to see the Emirates Lions go up 20-7.
Moukoro then got his second try in the 28th minute - also converted by Nolann Le Garrec - before Racing 92 had two tries ruled out late in the first half.
These five-pointers would have given them a handy lead, but the Emirates Lions had nothing of it and when they were presented with a last chance to score after the buzzer, they grabbed it with both hands.
From an attacking lineout, Ruan Venter shrugged off a number of tackles to barge over and where the score at the break could have been 28-20 to the French side, it was 27-14 to the hosts.
Ben Volavola scored shortly after the break to make it 27-21, but it only lasted a few minutes when Louw went over for his second try and Lombard also got in on the action, finishing after great interplay down the right. Nohamba converted both to make it a 20-point game.
Donovan Taofifenua, who had a try ruled out in the first half, got his five-pointer on the hour-mark, but that was it for the visitors, while the hosts were not done yet, with Nohamba scoring their seventh try after a superb run by Willem Alberts. A late penalty goal by Andries Coetzee saw them go past the half-century of points. Emphatic in every sense of the word.
Emirates Lions 51 (27) - Tries: Marius Louw (2), Edwill van der Merwe, Rabz Maxwane, Ruan Venter, Gianni Lombard, Sanele Nohamba. Converions: Nohamba (5). Penalty goals: Nohamba, Andries Coetzee.
Racing 92 28 (14) - Tries: Thomas Moukoro (2), Ben Volavola, Donovan Taofifenua. Conversions: Nolann Le Garrec (3), Max Spring.