The Brackley-based squad unveiled its 2013 challenger at Jerez on Monday ahead of Tuesday's opening test.
Although the W04 design looks similar to its predecessor, Brawn hinted as some hidden innovations.
"There are a number of concepts we have looked at, and no doubt when you see all the new cars you revisit some of the concepts, but this car has taken a good step forward in terms of aerodynamic performance," said Brawn.
"I think there are some innovative things on the car and you probably need to look a bit deeper to see them.
"We are comfortable with the designs and solutions we have come up with; but we will see the first signs in the next few weeks and certainly at Melbourne.
"That will be the real test of everyone's concepts and innovations - and that will be the true test.
"We are comfortable with what we have done."
Brawn revealed the front wing design will change later in the week, with more updates to be introduced before the start of the season.
"We have some things that we are quite excited about which will appear in the next few weeks," he said.
Brawn added his team is working on a passive double DRS like the one used by rival Lotus but admitted it was proving hard to get it to work properly.
"It is very difficult to get it to work, because there is historisis, or inertia, with the system, to get it to switch," he said. "That makes it very tricky.
"I wouldn't say that we have found a solution yet but we will doing some work on it in the next few tests and we will see where we are.
"We are keeping it there, we are still interested, we are still doing some work but I would not say we have found the right solution yet.
"I think that seems to be what most other people are experiencing, but we may see somebody find a solution and that will probably accelerate the development of the system."
The Briton, whose team finished in fifth place in last year's championship, said the goal for the year was to simply show continued progress.
"We have go forward. The commitment we have always made is to improve and we haven't always done that," said Brawn.
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