Can't imagine the tune you'd have to put on an engine to reroute the exhausts like thisRenault R31 Front Exit Exhausts (FEE) – Explained « Scarbsf1's BlogRenault have found a new solution to the blown diffuser concept. In fact they’ve turned it on its head. With an exhaust that exits at the front of the sidepods.
Last years teams reintroduced the blown diffuser concept, either by blowing exhaust gasses over the top of the diffuser, or by creating an opening into the diffuser to blow inside the diffuser. Both solutions created more downforce. With the latter solution now banned, it seemed the less effective over-blown solutions are all that’s left to race. However LRGP have found another way, blowing the front edge of the floor.
For a diffuser to create downforce it needs as much flow to pass through the venturi as possible. Teams arrange bargeboards and other aero devices to build up a high pressure region ahead of the floor to ensure the greatest mass flow underneath. Its then down to the expansion ratio of the diffuser to pull that flow through. Last years blown diffusers improved the expansion ratio, but not the flow ahead of the floor. What Renault have done in to lead the exhausts forward through the sidepods (about 1 meter) in-between the chassis and the radiators, then turn the exhaust 90-degrees to point it down towards the leading edge of the floor. The exhausts gasses follow the curved leading edge and round underneath the floor. This accelerates the flow under the floor for more mass flow and hence more downforce.
Problems with this solution are mainly to do with heat and engine mapping. With exhaust temperatures of 6-800c some clever insulation solutions are needed to keep hits heat from the fuel tank, radiators and a electronics. Then the Renault engine team lead by Rob White need to design exhaust tuning to deal with a far longer secondary pipe. typically longer pipes are better for low revs, somewhat contrary to the needs of an engine running at 18000rpm. Renault placed their KERS MGU and Battery underneath eh fuel tank, this was clearly to allow the packaging of the FEE. Unlike the McLaren F-duct, it is possible for this solution to be copied as no monocoque alterations are required.