2009 Acura ARX-02a
Images copyright  Michael J. Fuller
Text copyright Michael J. Fuller
Acura ARX-02a, Sebring WDWT 2009The ARX-02a's radiators are located in the side pods towards the end of the monocoque.  Air is directed through the front suspension shrouds and into the side pods.
Acura ARX-02a, Sebring WDWT 2009The monocoque is raised more so than on the ARX-01a and is further optimized for aerodynamic efficiency.  This provides room for a more aggressive front diffuser.  This would help gain back most, if not all and then some, of what was lost through the interaction of the front tires and the diffuser.

It can be argued that the ARX-02a has adopted an F1-style "zero keel" suspension mounting architecture.

The nose/splitter assembly locates onto the raised "chocolate finger" detail on the flange for the brake duct.  
Acura ARX-02a, Sebring WDWT 2009The diffuser's trailing edge is notched .  Best guess is that these notches help energize the diffuser's trailing edge flow.
Acura ARX-02a, Sebring WDWT 2009Some elements from the ARX-01a/b carry over.  Here we can see the serrated diffuser turning vanes.

Acura ARX-01b
Acura ARX-01b, Petit Le Mans 2008
Acura ARX-02a, Sebring 2009The Acura ARX-02a's front diffuser cross section is a non-symmetric wing profile that skirts Art 3.6.1 by coming to a blunt trailing edge.  We're to understand that the thickness of the trailing edge is around 30 mm, that being the undocumented dimension the ACO agreed upon to then categorize the cross section as a "non-wing".  

ęCopyright 2009, Michael J. Fuller