Elliot Daly starred as Wasps gained revenge for last week's thrashing at La Rochelle by beating the French side 21-3 on Sunday to boost their European Champions Cup hopes, while free-falling holders Saracens were beaten by Clermont.
Wasps throttled French Top 14 leaders La Rochelle in Coventry to gain some payback for a 20-point loss last weekend.
"If we can win our two games we have a chance of squeaking through as we have given ourselves a fighting chance," said Wasps director of rugby Dai Young.
"We possibly missed out on a bonus point today as we controlled the match but not the scoreboard and didn't turn our pressure into points, especially in the first half."
La Rochelle kicked off the game on maximum points after three consecutive bonus-point wins.
Last week the French side produced a brilliant attacking display, but on Sunday they were pinned back by a Wasps team seeking a victory that would keep alive their hopes of advancing.
England winger Daly smashed over in the corner to give Wasps the lead after 11 minutes. He converted the try and did the same after touching down again in the 47th minute.
Wasps never allowed the visitors to develop their attacking game and La Rochelle scored their first and only points when Brock James kicked a penalty on the hour mark.
The hosts had the last word when replacement hooker Tom Cruse powered over after a lineout. Danny Cipriani converted but Wasps could not add a fourth try to collect a bonus point.
Despite leaving the Ricoh Arena without even a losing bonus point, La Rochelle remain top of Pool 1, two points ahead of Ulster, who crushed Harlequins on Friday, and five clear of third-place Wasps.
- Saracens lose again -
Saracens, who were hammered by 32 points at home by Clermont in a weather-delayed game on Monday, saw their poor recent form continue with an agonising 24-21 loss in the second repeat of last year's final in less than a week.
The reigning European champions have now lost seven matches in a row in all competitions.
Smarting Saracens raced to a 13-0 lead with a try by Ben Spencer and a conversion and two penalties from Owen Farrell.
Morgan Parra responded with six straight penalties to put the home team five points ahead, but Farrell replied with three points of his own and Alex Lozowski scored an unconverted try to put Sarries back in front.
But in a chaotic and error-filled final 15 minutes, Parra kicked two more penalties to secure the victory which lifted the French club five points clear at the head of Pool 2 and dropped Saracens to third.
"We didn't make a good start and they took us by the throat," said Clermont coach Franck Azema.
"We didn't panic, we came back into the game by focusing on simple things."
Ospreys backed up last weekend's narrow win over Northampton by running in four tries to claim a 32-15 victory in Swansea to pile more misery onto the English sides.
All seven Premiership clubs were beaten last week, and Munster won 25-16 at Leicester in Sunday's final match.
The Irish outfit are now four points clear of Racing 92, who beat Castres on Saturday, at the top of Pool 4, with Leicester rooted to the foot of the table.
On Saturday, Leinster played 20 minutes with men in the sin bin and resisted intense Exeter pressure before beating the English champions 22-17 to stay top of Pool 3.
Montpellier saw off Glasgow 36-26 to take a firm hold on second place.
Bath bounced back from last week's narrow defeat at Toulon to beat the French giants 26-21 at the Recreation Ground and leapfrog them at the top of Pool 5.
Scarlets won 31-12 in Treviso to stay in touch with the top two.