Who brought the most upgrades to Barcelona?

For those with a technical eye on Formula 1, the Spanish Grand Prix is the busiest race of the year, as the cars have returned to their European homes beforehand and the teams arrive at the track with a host of updates.

Barcelona is a long-time key testing venue for F1, a familiar track to the teams. The layout challenges every element of the car, making it key for allowing teams to understand their cars' strengths and weaknesses, and the impact of new parts and development directions for the rest of the season.

Mercedes

There are technical novelties both on the chassis and power unit for Mercedes in Spain.

Lewis Hamilton has a new MGU-H and turbo for this weekend. These are new specifications updated without any token spend in order to resolve the reliability issues from the past two qualifying sessions.

Although the root cause is not known, it appears the insulation in the windings in the MGU broke down, causing a short circuit and therefore failure of the electric motor/generator.

Mercedes was only able to produce one update in time for this race, so Nico Rosberg retains the original design, though his car is fitted with a new combustion engine and MGU-K this weekend, after suffering MGU-K problems in the Russian GP.

On the chassis side the W07 is substantially revised with updated parts, each following the 2016 Mercedes philosophy of ever more serrated and twisted shapes for its bodywork.

Changes have been made to the nose tip, front wing endplates, turning vanes, sidepods and rear wing - making this a comprehensive update overall.

The slimmer 2016 nose with the narrow spaced wing pylons was tweaked with a slightly more pointed nose tip. This is an add-on part to the actual nose crash structure, so it isn't subject to a new crash test.

To the side of this the front wing endplates were changed with another part fitted to the endplate vane.

Now the vane ends with two twisted vanes, these complex surfaces appearing to be made from 3D-printed resin and bonded to the carbon fibre vane.

More serrations were evident on the front turning vane assembly, which bolts underneath the front suspension.

The old format - with four vanes joined at their base by a footplate - was first complicated with a series of six serrations to the footplate during testing.

Now the footplate is broken up from a single surface into seven separate surfaces. In turn this breaks up the airflow shed from the footplate into several smaller flows, providing more control with more intricacy.

In expectation of cooler European temperatures the sidepods have also been slimmed, with Mercedes going to the length of changing the inlet shape.

At the rear the monkey seat winglet has been changed to a three-element set-up with an extra slot put into the winglet.

Such myriad changes mean Mercedes has a substantially new car to run this weekend. The new parts are principally designed to improve aerodynamic efficiency at the rear.

Mercedes can then choose to run more rear wing for less drag, or maintain wing levels for more downforce at the same drag penalty as before.

Force India

Force India also brought a big update to Spain, having so far run the VJM09 in a very similar specification to the B-spec VJM08 at the end of last season.

This new package included a new front wing, revised sidepods, floor and rear wing.

The front wing is a Mercedes-style design with square arched tunnels in the area ahead of the front tyre.

Not only a significant investment, this also marks a change in influence for Force India.

Last year the team recruited ex-Red Bull aero staff and the car's direction has followed Red Bull's ideas.

Now it is taking its own direction with influence from Mercedes as well as other teams.

Along with the revised wing, the sidepods are now smaller, more sloped and slimmer at the rear.

In front of the rear tyres the floor slots are revised, with a two-slot arrangement directing airflow under the car to prevent the rear tyre wake upsetting the diffuser's performance - an important consideration given the high level of rake Force India now runs.

The rear wing's leading edge also gained a distinct stepped profile.

Again, this update is for the finer details of airflow, the drivers commenting that the changes are about the consistency of the aero performance rather than more downforce.

McLaren

Continuous chassis development has been a hallmark of McLaren's approach and it brought a big package of new parts for the MP4-31 to Spain, including a new front wing, brake ducts, sidepods and floor.

This is the third new front wing specification of the season, not including the little add-ons that get made to the basic design.

This latest design is more outswept and complex. The outswept shape is evident from the wing's leading edge starting further inboard, creating a wide flat footplate around the endplate area.

The wing then arcs out towards the front tyre. This reduces the wing's working area, but improves airflow around the tyre.

Adding further complexity is yet another flick to the cascade winglet arrangement, and slots carved into the inner tips of the flaps.

Almost as complicated are the new front brake ducts, which move away from last year's 'clam shell' design.

The inner shape of the new duct is flatter and grabs air from a dedicated scoop, not the gap between duct and wheel.

This change works with the new front wing to manage the airflow around the front tyre.

Inside the wheel the duct is also new, with more scope to route air around the brakes and out of the wheel.

This flow is used both as cooling and an aerodynamic aid.

Less obvious are the sidepod changes - slimmed down for cooler conditions.

Ferrari

Ferrari was expected to bring more upgrades to Spain, but changes were largely confined to the rear wing - which was updated to a profile with a slight angle to its leading edges.

In turn the endplate was subtly revised, but elsewhere the Sochi-specification front wing was used and no other significant upgrades were visible on the car - quite a surprise given the chase Ferrari is in at the front of the field.

Red Bull

Like Ferrari, Red Bull did not bring the big updates perhaps you'd expect for Barcelona.

Friday was spent diligently running aero rake, flow-viz tests and playing with brake duct specifications.

As the aero testing was largely focused on the front wing, there may be some small geometry changes to the outer span.

There were no signs of the front wing 'shark teeth' seen at Shanghai.

Williams

For Williams the key visible technical novelty was the bargeboard design tested at Sochi.

Following the general principle of the old parts, the new bargeboard features a leaned-back shape, the vertical leading edges being slanted towards the rear of the car.

Across the upper portion of the bargeboard Williams used to have three separate vanes, now this has increased to four.

As with Mercedes' multiplication of edges, each vane sets off its own vortex, creating increasing sophistication in the wake shed from the bargeboard.

Felipe Massa was among several drivers who altered their cockpit environments to improve comfort in the car.

Massa had two seat specifications to try during free practice, one marked 'deep shoulder'. His engineers also added foam inside the cockpit to make him more comfortable.

Renault

Finally starting to ramp up its development programme for 2016, Renault will test many new aero and suspension parts at next week's test in Spain, as well as running its new specification power unit for the first time.

For the grand prix, updates appear to focus on different front wing details, with three specifications spotted in the garage.

Each is based on the same basic front wing, but there are two different flap configurations, while the third wing features the cascade winglet seen in China.

Renault also has a different rear wing specification here, but this is simply a different, higher downforce configuration rather than an update.

Haas

A revised rear wing is the second technical update we have seen on the Haas this season.

While not a huge upgrade, the Dallara-designed parts tested in the Ferrari windtunnel affect the top rear wing element, endplate and monkey seat winglet.

With a revised shape to the two rear wing elements, the endplate also gains a second slot below the wing, to reduce drag.

Below this, and critical to maintain stable aerodynamics around Barcelona's long corners, the monkey seat is larger and more complex.

The multi-element winglet works with the exhaust and diffuser to create upwash to maintain a clean airflow under the top rear wing.

Like Sauber, Haas also introduced the new Ferrari engine specification.

Manor

A sign of positive times at Manor is the update brought to Spain, featuring a new front wing, turning vanes, rear wing and an auxiliary tank in the sidepods.

Most visible are the new turning vanes under the nose. These are more twisted and curiously the leading edges point upwards slightly.

The other obvious addition - being yellow and spotty - is a bag tank fitted to the front of the right sidepod.

This flexible tank has been made to fit the space under the sidepod inlet.

Unable to carry fuel in this area, the bag is likely to be an auxiliary oil tank to top up engine oil during the race.

This is common on all F1 cars and not unique to the Manor car or Mercedes engine.

Sauber

With times remaining hard for Sauber the car is unchanged, but it did benefit from the updated power unit specification from Ferrari.

The updated parts allow the turbo to be run harder for longer, after reliability concerns forced teams to reduce turbo pressure and speed on long straights.