The Woking-based outfit made the decision to part ways with former engine-supplier Honda at the end of the 2017 campaign after three immensely disappointing years together.
McLaren, who last won the Constructors' Championship in 1998, have since joined forces with Renault for 2018 and the initial signs are looking positive with good progress being made ahead of the new season.
Brown admits there are still certain areas that the team need to make improvements in but he is confident the new power-unit will have a huge bearing on the overall results.
"We're not perfect, we certainly have room to improve, our pit stops aren't good enough, we need to be top three, so we have some areas we can improve," he said. "But the lack of power was our single biggest area of weakness so I think when we get the Renault in the back we should see a substantial difference in Australia."