Jonathan Rea stretched his World Superbike lead to 124 points after winning both races at Portimao.
The Ballyclare rider edged out Kawasaki team-mate Tom Sykes in an exciting race one to win by 9.38 seconds.
Rea completed the double in race two, winning by 5.4 seconds from Davide Giugliano with Leon Haslam third and Chaz Davies fourth.
"Kawasaki have given me a great bike and I have an incredible lead but there is still a long way to go," said Rea.
Sykes is the closest challenger to Rea, who has 10 wins and four second places from 14 outings this year.
The pair fought out a long battle in race one, with the added intrigue of pit stops to change tyres when rain made conditions treacherous with six laps left.
"I got an incredible start and I was just waiting, weighing up where to pass, then managed to get in front of Tom midway through the race," said 28-year-old Rea.
"The rain came on and it was a little bit scary as I haven't done many laps on the Kawasaki in the wet. It was pretty stressful in the end but I got the win."
Rea only qualified in eighth position as a crash in Saturday's Superpole session brought a premature end to his session in the 15-minute shootout to decide grid positions.
He made a fine start to race one from the third row of the grid, moving up to fourth by the first corner, and then second by the end of the first lap.
Rea overtook Yorkshireman Sykes on lap 11 of 20 but all riders were forced to come in to change tyres when the rain began to fall, making conditions treacherous in slick tyres.
Rea pitted first, Sykes one lap later, and the pair traded places over the closing laps, before the series leader finally got the better of the Englishman, when his team-mate suffered a mechanical problem as he was about to go out on his final circuit.
Welshman Chaz Davies completed the podium on his Ducati, with Giugliano fourth and French Honda rider Sylvain Guintoli fifth.
Alex Lowes was 10th and Leon Haslam re-mounted to finish 12th after sliding off with four laps left.
Rea heads the standings on 305 points, with Sykes moving up to second on 198, Haslam third on 182 and Davies fourth on 171.