Newey admitted the lack of regulation changes for the upcoming season meant there was no big reason to go for a revolutionary design.
"It's an evolutionary car," said Newey during the launch of Red Bull's ninth Formula 1 single-seater.
"There were no big regulation changes over the winter. The most significant change is not the regulations, it's the new Pirelli tyres. We had a quick test in P1 in Brazil but it was very hot and on a green track and in truth we didn't learn a lot."
He added: "It's really been a case of refining the RB8. There are no huge changes. It's very much an evolutionary car. All the principles the same as last year.
"The devil has very much been in the detail with this car. We've tidied up some bits that we felt could be improved on. Development is now the key through the year."
Newey said understanding the new Pirelli tyres will be as key as it was last year, with the Italian manufacturer having altered its products for 2013.
"We need to continue to understand the tyres," he said. "Every time we thought we understood them last year, some fresh surprise would come in and we'd realise it wasn't complete. And they've changed the tyre anyway this year.
"Past experience is that it's only when we get out testing that we really find out about the tyres."
Newey acknowledged that having the car ready in time for the first test of the year was a great effort by Red Bull given how long the 2012 championship battled extended.
"We obviously had a very tight championship battle last year and it was difficult trying to develop last year's car and do the research into this year's car," he said.
"It gave us a very tight timeframe to manufacture this car. To have it here today, two days before the first test, is a remarkable effort."