McLaren's MP4-28 is an "ambitious" concept with great development potential, according to the team's managing director Jonathan Neale.
Neale said McLaren had deliberately chosen to try new avenues with its suspension and exhaust even though an evolutionary design was an option with the regulations broadly unchanged for 2013. The front suspension is now a pull-rod configuration, while the sidepods and the rear bodywork have been reprofiled.
"When you have small regulation changes, do you do something conservative or do something more ambitious?" he said. "On this occasion we have chosen to be more ambitious. We believe that rather than run out of gas in the middle of the season it gives us more development potential."
Team boss Martin Whitmarsh is confident that McLaren will start 2013 in even stronger shape than it ended last year, when it won the final two grands prix in America and Brazil.
"We finished last year with undoubtedly the quickest car," he said. "We could have continued to develop that car and found some performance.
"In changing things you inevitably step back, but this car is already quicker than the car we finished last year with. In all that we are looking at, this car is responding very well. We had a detailed technical review yesterday and you cannot help coming out of this thinking we have a competitive car.
"Our competitors are off the radar screen and you cannot rule out them having a Eureka moment, but we are pleased with where we are with this car today and this car will look different before the season."