Mercedes has kicked off its running in the second Formula 1 pre-season test at Barcelona with a number of new aerodynamic components in the pursuit of extra performance.

The team launched with a front wing design noticeably different to the others seen on the grid, most interestingly using an endplate design which appeared to guide airflow inwards, rather than the outwashing endplates used by everyone else.

Although it seemed that the combination of the endplate and front wing flap adjuster together could ultimately channel airflow around the tyre, Mercedes has resurfaced for the second week of testing with a new design.

The new endplate now directs airflow outboard, and the top corner at the trailing edge features a small square cut-out - which ends the production of the tip vortex from the endplate sooner, which can then be guided outwards by the airflow from the wing spilling over.

The nosecone has also undergone a slight redesign, where the top edges either side of the Pirelli logo have been tucked in.

This gives airflow an easier path to drop down onto the 'cape' area, at which it's able to develop a greater low-pressure zone underneath.

Together, these changes seem to hint at Mercedes's first steps to iron out the handling issues reported by the drivers after the first test, aiming to increase front-end downforce.

Two fins have been placed on top of the chassis bulkhead too, either side of the S-duct outlet, offering extra control over airflow around the suspension components and down the flanks of the chassis.

Furthermore, the floor has also showcased a number of new additions, including six new fins along the edge.

Three of these assist with directing airflow outwards through the primary floor slot, while the other three are grouped together to collectively develop further outwash ahead of the diagonally-cut rear slots in the floor.

The team has also added a brand new T-wing to the bottom of the engine cover, double-stacking the elements to assist with cleaning up airflow ahead of the rear wing and eke out a little extra downforce.

Retaining the strakes at either side of the wing, a vortex can continue to form and fold below the rear wing, increasing the effect of the suction surface.

Toro Rosso has also kicked off testing with a number of new parts, debuting a new rear wing with a straighter leading edge along with a new T-wing.

McLaren driver Lando Norris headed the first day of Formula 1's second pre-season test despite stopping twice on track, beating long-time pacesetter Pierre Gasly by 0.006 seconds.

Norris completed 38 laps in the morning but missed the final hour and 40 minutes of that session when he stopped with a reported loss of hydraulic pressure.

He completed solid mileage when running got back underway after the lunch break, but did not improve on the 1m22.306s he set shortly after 10am local time until 5:15pm when he recorded a 1m19.264s on the C5 Pirelli tyre.

That was the first of three short runs the McLaren driver completed, with the second hoisting him up to fourth before he shot to the top of the times with a 1m17.709s lap on the C4 compound.

But Norris stopped again exiting Turn 2 with just over 20 minutes of the session remaining, bringing out a third red flag of the day that left just 12 minutes of green-flag running when the session resumed.

Red Bull driver Gasly had been fastest in the morning until a late improvement from Alfa Romeo's Antonio Giovinazzi, and was denied top spot again by Norris's late effort.

But his lap of 1m17.715s on the C3 compound was more than a second faster than the best effort a Red Bull-Honda achieved in the first week of testing, while Gasly also recorded a session-high 136 laps.

Lance Stroll ended the day third in the Racing Point-Mercedes, a mere 0.115s shy of Norris's time with 82 laps to his name.

Sebastian Vettel spent the afternoon in Ferrari's SF90 and had a brief spell at the top of the times, before spending the latter part of the afternoon concentrating on long runs on the C4 and C3 compounds.

While Vettel logged 81 laps, his teammate Charles Leclerc was limited to just 29 after Ferrari spent much of the morning checking its cooling system.

He ended the day with the seventh-fastest time.

Morning pacesetter Giovinazzi ended up fifth, failing to improve on his early benchmark in the afternoon, while Toro Rosso's Alexander Albon jumped up to sixth late on with a 1m18.649s lap on the C4 tyres and was one of four drivers to surpass the 100-lap mark.

Kevin Magnussen (Haas) and Williams driver George Russell were the other two aside from Gasly to pass that count, and ended the day eighth and ninth in the times.

Russell spent some time in the morning completing more checks for Williams, which missed the opening two days of last week's first test, but was able to attempt performance runs in the morning before focusing on longer runs in the afternoon.

The top 10 was completed by Renault's Daniel Ricciardo, who set a best time of 1m20.107s and logged 77 laps after taking over for the afternoon from teammate Nico Hulkenberg, who propped up the times.

Lewis Hamilton enjoyed a trouble-free morning focussed mostly on long runs on the C2 and C3 tyres, but the same could not be said for Mercedes teammate Valtteri Bottas - who stopped on his out-lap in the afternoon with an oil pressure issue.

Mercedes changed its engine as a precaution, but Bottas did make it out before the end of the session and completed a further six laps to end the day in 11th.

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As the 2019 F1 cars hit the Barcelona track last week for testing, so we saw some of the innovations that were either unclear or hidden altogether in the respective launches of the cars the previous week. Here we look at five of the most intriguing developments.

1. Ferrari’s radiator side exit

Ferrari have created an airflow exit for the radiators directly behind the radiator (the red arrow in the illustration above). This is only a small part of the total exit area, with most of it still exiting at the rear, around the exhaust, but devoting this small area in the side to venting the hot air brings two potential advantages:

1. The outlet area at the back can be correspondingly smaller, allowing the bodywork to be more tightly-waisted there, which helps accelerate the airflow, increasing downforce.
2. The flow can be aligned with that coming from the vortex generated by the hump in the bodywork ahead (the blue arrow), increasing the speed of the air flowing out of the radiator outlet and therefore its cooling capacity.

2. Renault’s rear-wing endplate winglets

Renault ran in the first week of Barcelona testing with a rear-wing endplate quite different to that fitted at the launch – and to that on any other car. In the transition between the two permitted wing widths at the upper and lower sections (wider at the top, narrower beneath), Renault have introduced a sequence of three turning vanes within the endplates that will generate a small amount of downforce in addition to that from the wing elements.

3. Alfa Romeo’s front wing

By the time of Barcelona pre-season testing Alfa Romeo had revised their initial front wing to a less extreme version of the same concept, with the elements at the outer ends ahead of the tyre still much skinnier than those in the main part of the wing, in an attempt to aid the airflow ‘outwash’ itself around the tyre.

But whereas the original outer elements were almost flat, in this second version they were partially raised. In the main part of the wing, inboard of the tyre, there are just four elements rather than the permitted five. This gives a greater downforce-generating surface area to compensate for the skinniness of the five elements ahead of the tyre.

4. Ferrari’s ‘extractor’ wheels

Ferrari experimented with their own version of the ‘extractor’-style rear wheel rims, as introduced by Mercedes at Spa last year. Holes on the inner face of the wheel align with those on the exterior to extract hot air more quickly from the wheel rim, thereby transferring less of the heat to the tyre. The nodules around the outer face of the rim add to the extractor effect and also provide a greater surface area over which to spread the heat – again reducing the heat transfer to the tyre.

5. Red Bull’s multi-element rear brake ducts

The new aero regulations of 2019 have left the rear brake duct area relatively free – and Red Bull have taken maximum advantage of that to introduce a multi-stacked series of elements atop each duct. Because of where the ducts are mounted, these elements produce downforce that acts directly onto the wheel, without being compromised by having to act through the suspension. Since 1969, the regulations have not permitted wings to be directly mounted to the wheels. But because this is ostensibly a brake duct with a shape that just happens to generate downforce, it gets around this ruling in a small way.

Lewis Hamilton fears Ferrari could hold an advantage of half a second over Mercedes as pre-season testing in Barcelona draws to a close.

Ferrari enjoyed a strong start during the first test and has carried on that form to set the fastest two times of pre-season so far, with Sebastian Vettel’s 1m16.221s on the final morning just edging teammate Charles Leclerc by 0.01s. Valtteri Bottas put Mercedes 0.34s further back on Friday, but Hamilton believes the gap between the two teams could be even greater than that.

“Ferrari are currently fastest,” Hamilton said. “I’m not quite sure (by how much), but I think it is potentially half a second. Something like that potentially. We will be analyzing a lot from this test and there will be some mods that we will try to implement for the race. There is obviously not a lot of time but over the next week we will try to gain another tenth at least in our understanding of the car.

F1 Testing: Week 2 in Barcelona by the numbers