Having finished on the podium in all the eight races of the championship, organised by the Madras Motor Sports Club, including five in the first round at Dubai last month, Defourny consolidated his position on the leaderboard with 173 points, ahead of Chadwick (129).
Two more races are scheduled for Saturday.
Defourny said: "It could or rather, should have been better this week. After qualifying for pole position last night, I made a mistake in the first race today and finished second. In the next race, I got hit from behind at Turn-1 when one of the competitors (Danial Frost of Singapore) spun.
"There was some damage to the car and I managed to finish second. In the third race today, after we repaired the visual damage to the car, there was a lot of vibration in the left rear, but I managed to pull away to win."
Defourny was at his best in Race-3 which he started from pole position and won quite comfortably despite the vibrations, while Estner came in second followed by Patrik Pasma from Finland.
The damage to Defourny's car was the result of a collision before Turn-1 immediately after the Race-2 start between reverse-grid pole-sitter Petr Ptacek (Czech Republic) and Singapore's Danial Frost.
The incident allowed Chadwick, who had started third, to get a jump on the pack, leaving Dylan Young (Australia) and Defourny to scrap for second and third spots.
The Belgian finally moved past the Aussie, but by then, Chadwick was long gone. The trio held position to the finish. For Chadwick, it was her maiden win in the championship after three second places in Dubai round.
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