Tech: Mercedes' S-duct explained

With 2015 development finished for most teams, the tech spotlight at the Brazilian Grand Prix has been on what the pitlane is trialling for next year - and champion team Mercedes caught the eye with one particular innovation.

MERCEDES ADDS AN S-DUCT

There was a huge media focus on Mercedes in free practice one at Interlagos on Friday, as both W06s were fitted with a bulged scuttle panel.

It appears Mercedes was testing an S-duct: a ducted nose set-up that cleans up the airflow over and under the chassis.

These ducted noses first appeared on the Sauber, when stepped noses were introduced, and since then Red Bull, Toro Rosso, McLaren and Force India have all run versions of them.

They take airflow from under the nose and duct it over the top of the chassis. This keeps the airflow over the top of the car attached, improves the flow under the nose and allows a useful reduction to the depth of the nose cone too.

It is possible to retro fit the design to a car, but it's better if the shape of the front bulkhead and nosecone are optimised to package the ductwork.

Mercedes replaced the usually smooth scuttle panel covering the front inboard suspension with a new part, made with two distinct bulges moulded into it.

The key shape was the exit duct. This rear facing outlet was taped up on Lewis Hamilton's car and run open on Nico Rosberg's car, so clearly Mercedes was not intending the full set-up to be run at this stage and was conducting a trial.

There was a lateral bulge made in the new panel - its shape mimics the opening in the chassis underneath, which houses the coil sprung heave element.

This suspension part was no larger than usual, so the extra clearance was either to replicate the planned bodywork height for 2016, or to accommodate ducting to feed the exit duct. Yet this panel had no obvious ducting leading to it and no inlet visible under the nose.

That was further evidence that this was not a fully functioning S-duct, and it transpired that the panel was a test for 2016, designed to check that the duct and a higher chassis top would not obstruct the drivers' view from the cockpit.

There were also some suggestions the set-up required a new nose cone to accommodate the inlet below the chassis.

I believe the greater problem may be a lack of a suitable hole in the floor of the car to route ducting through, unless a duct can be packaged inside a taller nose to feed the exit.

We will need to see if the panel gets a second run in Abu Dhabi and if it's complimented by the inlet and ductwork to feed it. Otherwise it may be 2016 (and the arrival of the W07) before we know if Mercedes is adopting an S-duct concept.

RED BULL GETS ITS NEW RENAULT

Renault waited until 15 races passed before expending 11 of its remaining 12 power unit development tokens and upgrading its internal combustion engine (ICE), and we had to wait a further two grands prix before Red Bull decided to take the plunge and actually try the engine.

It's been clear all year the Renault package has an excellent ERS, but lacks horsepower from the V6 turbo engine.

So, with a spend of almost all of its remaining tokens from the winter of 2014, the engine finally gains a new combustion and top-end set-up.

This should boost power and hopefully reduce the unit's sensitivity to heat, though Red Bull estimated the laptime gain at only 0.1-0.2 seconds.

The former benefit will be immediately obvious in Brazil's final sector, but to take advantage of the thermal gains will require a reworking of the car's sidepod set-up, downsizing the coolers, to improve aerodynamic performance without a loss of power.

Only Daniel Ricciardo ran the updated PU in Brazil, with team-mate Daniil Kvyat expected to get his version at the final race in Abu Dhabi.

McLAREN ADAPTS TO NEW RIDE HEIGHT PHILOSOPHY

Continuing to press on hard with development on both fronts, McLaren-Honda had new parts again for Brazil.

The key change on the chassis was a further reworking of the diffuser.

As the team progresses with its testing of higher rear ride-heights, as exploited by Red Bull and others, the diffuser needs to be able to control the airflow with a far greater gap to the ground.

This is helped by the multiple fences inside the diffuser, so it has been resized and repositioned to work better at the higher ride-height.

TORO ROSSO TRIES STRAIGHTLINE SOLUTION

A small but important update for Interlagos is a refined rear wing on the Toro Rosso.

The flap's trailing edge is tapered slightly towards the tips, which reduces the flap's angle of attack at the endplate, and reduces the drag-inducing vortices that the intersection between wing and flaps creates.

As Toro Rosso is still choosing to run the old-spec Renault V6, with its power deficit, the reduction in drag helps the car's performance through the final curve and straight.