6 hours race at Nurburgring has provided a great opportunity to see again prototypes with Aero kit designed to maximize downforce, a huge turnaround from maximum efficiency target necessary on legendary Le Mans 24 Heures.
The race has been considered a key point of the WEC season that is looking forward to eventually reshape itself after withdrawal of Porsche almost certain, following Audi.
Porsche has shown a clear supremacy in term of performance and pace consistency heading to a win with very weak battle form Toyota.
High downforce kit used by Porsche shows some interesting details and concept especially on front part of the car.
Front fender leading edge is less extended forward and a much larger dive plate is mounted on top of splitter edge.
Dive plate design is common on all LMP cars showing a surface basically horizontal generating downforce using high pressure coefficient ahead the fender nose with limiting vortex generation.
Cuts on the external edge, closed to fender intersection, are design to better control flow on side surface.
Top lowers are also changed as we will see in more details in next picture.
Porsche 919 Hybrid - comparison of High Downforce front nose (left) with Lower Downforce version
Front Lowers collocated between fender inside surface and front nose are clearly different comparing High downforce kit (right) with solution seen during test at Monza.
Due to different upwash generated by splitter and flap configuration is necessary to create major duct to better control the flow on top of these panels.
This is the reason behind adoption of 2 elements instead of 3 and bigger vertical slot .
Porsche 919 Hybrid - details of front Lowers used at Monza (left) and modification introduced with HD aero kit (right)
A small lateral “air dam” is mounted on splitter side edge to create downforce preventing that flow wrap under the splitter. Positive pressure coefficients at the base of fender nose generate downforce and flow tend to turn under the splitter extremities. This is limited by the action of this longitudinal fence.
Porsche 919 Hybrid – Splitter side dam used on HD aero kit
Blocking effect under the nose is reducing downforce generation and causing drag increase.
As outlined several time the splitter-flap configuration of the nose is to be considered as a front wing in ground effect. As such, the upwash created on the flow and pressure variation on longitudinal position under the nose is causing boundary layer separation and blocking effect on lower part of the chassis.
As adopted since years on F1 the “F-Duct” is providing a different path to the lower airflow helping extending efficiency on front downforce generation.
Porsche 919 Hybrid - Front “F-Duct”, details of inside flow channel, duct entry behind nose and discharge exit on top of the nose.
Rear nolder are used on trailing edge to increase downforce, creating an equivalent curvature on the upper surface. The effect is also sustained by the blowing effect of exhaust gas pipes .
Rear nolder and front dive plate combination are very effecting way of trimming longitudinal aero balance of the car.
Porsche 919 Hybrid - Detail of the rear nolder