McLaren has become the first team to take advantage of the final green-light for double-decker diffusers in Formula 1 by fitting an interim version to its car in Shanghai. The team has added a small winglet beneath the crash structure and above the dipped center of the diffuser, which is likely to be the first step of a major development push in this area.
The change for China is far from being a full double-decker design, which is expected to appear in subsequent races and is more akin to Toyota's narrow diffuser extension. By adding this flap, the revised diffuser is now both taller and longer. The flap rises more than 90mm above the 175mm maximum and extends around 40mm behind the permitted 350mm length. But as the flap sits within the 150mm exclusion area for the rear crash structure, it is perfectly legal.
McLaren appeared with a new diffuser in its last test before the season started. It had a lower center section, which was expected to be in preparation for a double-decker design, once the protests had been cleared up.
In its current guise the diffuser is a small improvement over the version run in the last two races, but scope still exists for a full double-decker conversion soon.
This fuller conversion may require changes to other parts such as the rear crash structure and rear suspension, as well as the aerodynamic parts upstream of the diffuser such as the front wing and bargeboards.
Other teams have been developing these diffusers in expectation of the FIA court of appeal ruling with Renault possibly introducing its version of a double-decker diffuser this weekend. Most teams are expected to fit the design by the Spanish Grand Prix, although Red Bull Racing may have to wait until as late as either the Monaco or Turkish race before its version is ready.