Piquet is now confidently looking towards the remaining rounds of the TRS at Taupo and Manfeild. "Each day I've been getting better in the car," said Piquet.
Once he had established a lead, Piquet managed the gap back to second placed James Munro from Christchurch, who had made a great start from third on the grid.
"Jehan (Daruvala who finished third) piled on the pressure," said Munro, "but I managed to hold him off."
Earlier, Guanyu Zhou had won the reverse grid race from Invercargill's Brendon Leitch who started the main event from 12th on the grid and managed to advance to 10th, but dropped to fifth on the closely contested points table.
Series leader Lando Norris was supposed to start from the front row of the grid in the main race but was penalised eight places for an incident in the preliminary race and had to be content with a sixth place finish.