NOTE: Update on McLarens Snorkel\Rear wing here http://wp.me/sNdA9-235
As McLaren continue to use testing rigs to map their cars aerodynamics, the importance of the snorkel on the top of the chassis is becoming apparent. On Friday The car lapped with an array of sensors attached to the rear wing. However, there was an additional sensor mounted inside the snorkel. Raising the question why would you want to test rear wing and driver cooling simultaneously?
This Snorkel, is an apparently innocuous looking part, which was at first believed to be solely an inlet to cool the cockpit. Several teams add similar inlets in this area to supplement the inlet in the tip of the nose. The cockpit houses the power steering rack, hydraulic lines and electronics boxes, so cooling is often required. However the initially simple inlet has been superceded by at least two more shapely snorkel-like derivatives each with an apparently unnecessarily complex double wall construction creating smooth narrow inlet and a streamlined outer surface. This snorkel has been present ont he car through out all the cold and wet testing sessions, suggestion its purpose goes beyond a simple primary purpose of cooling.
One rumour around the internet suggests the inlet is linked by a duct to the shark fin\blown rear wing. At first appearing to be simply a wild rumour, that the snorkel is blocked by the drivers knee to alter the rear wing airflow. However the presence of the airflow sensor along with the rear wing test rig, suggests there might be a link after all. The rumours suggest the drivers left braking leg, which sits unused on long straights could be used to alter the flow from the snorkel to the rear wing duct, where a valve alters flow through the blown slot to stall the rear wing. This would reduce downforce and also drag, which would allow a higher top speed. Then the driver moves his leg to start to brake for the next turn the valve switches airflow back to normal, the wings airflow reattaches and provides the downforce needed for the turns. This sounds both feasible and far-fetched at the same time.
It would be hard to link the rear wing and snorkel with any certainty, but any input from the driver that would alter the cars aerodynamics as the rumours suggest would certainly be an area of greyness in the rules and liable to protest come Bahrain.