The three-week break since the Malaysian Grand Prix has given Formula 1 teams the chance to bring a multitude of new parts to China.
Friday free practice was used to trial new developments and measure their performance with bespoke sensor pods. Every team had something new.
A weak point of Red Bull's car in recent years has been the lack of straightline speed.
With its overall lap time advantage, the car could be set up for higher downforce and therefore higher drag as it was rarely vulnerable to being overtaken.
Red Bull is running with small amounts of rear wing © XPB
This year, Red Bull does not have the same edge, so the RB9 has been running very small amounts of rear wing.
With the long back straight at Shanghai, the rear wing is set much flatter. Vettel even tested a new rear wing with near-Monza levels of angle. This will boost Red Bull's top speed.
The downforce lost from the rear wing is supplemented by that being produced by the diffuser, which is being sealed so effectively by the exhausts.
With the F138 still not quite on the pace, Maranello's development rate is very high.
Two obvious new additions have been made to the car this weekend; another front wing variation and new turning vanes under the nose.
Ferrari's front wing features a new endplate, evolved from versions seen in testing.
Like Lotus's, the Ferrari endplate also features slots in the horizontal part running along the footplate.
The footplate is there both due to the regulations on minimum surface area for the wing endplate and also to help seal the pressure created under the wing.
By splitting the footplate with two slots as seen in China, Ferrari is also trying to get the airflow passing around the plate to flick up and around the front tyre.
Ferrari's new turning vanes © XPB
Also aiding airflow around the car are the new turning vanes under the front suspension. Ferrari had initially used a double pair of vanes, now it has split the vanes into three elements to fine-tune the vortices they shed.
These vortices pass back under the raised chassis and control the airflow passing around and under the car.
Devices such as these are key to getting the rear aero working as they divert the airflow into the right pressure and direction to get the diffuser working.
New rules in 2009 limited how many vanes could be placed around the front of the car and now these devices are largely limited to an area 25cm from the car's centreline.
Along with the inner cascades on the front wing and the front wing mounting pylons, the effect of the devices is known as the 'Y250 vortex' because it is 250mm sideways (the Y direction in CAD software) from the car's centreline.
Having brought a successful upgrade to Raikkonen's E21 in Malaysia, the Lotus team now has two sets of the new-specification front wings, sidepods, floor and exhausts, so that both drivers can run the development parts for this weekend.
New parts seen in Friday practice include new pod vanes and revised rear wing endplates.
Pod vanes are the vertical vanes that are outboard of the front of the sidepods. These parts both separate the front wheel wake from the sensitive bodywork around the back of the car, but nowadays are also shaped to guide airflow over the exhaust outlets for a better Coanda effect.
Lotus is bringing several new parts © XPB
Lotus has kept the old pod vane, but added an additional vane inside it that forms a 'U' shape to better direct the airflow towards the exhausts.
This new part is probably a secondary upgrade to aid the Sepang-specification sidepods.
The new rear wing endplates are an evolution of an idea seen late last year. The outside of the endplate features strakes broadly aligned with the vanes on the rear brake ducts, adding to the ducts' downforce production.
There are three new strakes, each broken up into three separate pieces. They are very narrow and must fit inside the small 50mm allowance created in the rules for the rear wing endplate width.
With more time to develop its troublesome car, McLaren arrived in China with more upgrades than the hastily-modified floor run at Sepang.
The MP4-28 featured substantially revised sidepods. The car also appeared to test some parts briefly seen in Malaysia and a new front ride height set-up.
In order to gain a more powerful Coanda effect from the exhausts sealing the diffuser, the sidepods have been reshaped. The top surface now sweeps down more steeply. This lower sidepod line requires a large bulge to clear the engine and exhausts.
The exhaust outlet also appears to have been brought forward. This should have the effect of making the diffuser less sensitive to the car being on or off throttle.
McLaren also ran a small ramped winglet around the rear crash structure in Sepang. This was tested again in Friday free practice.
One strange incident that occurred in the pitlane - other than Sergio Perez running into the pitlane entry barrier at the end of Friday morning practice - was a small fire on Jenson Button's car. Button brought his car in with delaminated front tyre and smoke poured from the splitter. It then ignited into a small fire, but after changing tyres the team allowed the car to exit the pit without needing to extinguish the flames.
McLaren is the team with the most updates © XPB
Although the fire was partly caused by Button's damaged tyre reducing ride height, it's possible that McLaren is trying to run the front of the car as low as possible in order to regain the impressive pace seen in the Jerez test.
At this test, a mis-assembled heave element led to the front ride height getting too low when on out track.
Excessive wear was also evident on the Perez car as it was craned away from the track. McLaren is exhibiting a lot of wear to the front of its skid blocks. This suggests McLaren is risking plank wear for greater pace.
An obvious change this weekend is a revised front wing.
Like other teams, Mercedes finally followed the trend for curved split vanes mounted under the chassis, rather than the straighter vanes fitted in the same place last year.
On the front wing, the cascades have been changed. The inner winglet has been deleted and replaced by a curved endplate section.
Mercedes has raced with the front wing cascades featuring one large wing element and a tiny narrow element mounted inside it. It is this inner winglet that has been removed.
The endplate section it was mounted to has now been curved inwards to replace some of the function of the winglet.
Although these cascades are winglets, their purpose is more about conditioning the airflow to allow it pass around the front tyre than creating downforce.
Another team struggling to revive the fortunes of its 2013 car, Williams brought more new parts for its FW35. There was yet another front wing variation and it was matched to new turning vanes.
The team's simpler 2013 front wing has been mated to revised cascades. This time, the usual twin pair of siamesed winglets have been swapped for a winglet attached to the endplate and another winglet mounted on its own vertical stalk.
Williams's new front wing © XPB
The standalone wing idea is not new in F1, as it has previously been used by both Jaguar and Toyota. Coincidentally both teams had the influence of aerodynamicist Mark Gillan at the time. So it's likely that this development was being incubated in the time before Gillan left the team before the start of the season.
Mated to the front wing and oversized front wing mounts are new turning vanes under the nose.
Williams had been one of the few teams to still have vanes attached under the nose cone itself.
Now, the vanes are mounted under the chassis like most other teams. Its new vanes are the typical two element design. They curve outwards under the car and feature a slot to further boost the creation of the Y250 vortex.
Marussia's MR02 sports new fins © XPB
Again running both the 2012 specification wing and nose cone and the newer front wing design, the MR02 gained some new fins atop the sidepods.
A single fin on the front of each sidepod has been fitted. These create a vortex that passes over the sidepod and helps redirect the exhaust flow towards the diffuser.
Most other teams run these vanes, albeit in pairs of two or three. But this is a good step forward on the initially simplistic Marussia, which shows it is gaining new complexities from its windtunnel programme.
Friday test sensor pods
Teams are now permitted to run additional sensors during Friday practice because of the ban on in-season testing and the heavy restrictions on straightline running.
By running extra sensors, teams are mainly checking for air pressure or temperature. On Friday in China, several teams ran additional temperature sensors.
Williams, McLaren and Sauber used additional pods for testing in the opening practice sessions. Inside these pods are infrared cameras, which used to be used solely for checking tyre temperatures, but more recently are also used to check the exhaust flow.
Looking close at the Sauber set-up we can see how complex these pods can be. The pod is mounted in one of the locations stipulated for the FIA cameras.
This means there are mountings for the unit to bolt to and also space for wiring to pass into the pod. The pod itself is aerodynamically shaped and made from a plastic-like composite material via a rapid prototyping process.
The unit encloses a small infrared camera, which will be angled to look at the rear bodywork or tyre.
Data from the camera will be interpreted as a temperature range, so that teams can get a detailed understanding of the temperatures around the back of the car.
One reason for the sensor pod described above is the new parts fitted around the sidepods. Although these changes were hard to detect, Sauber's new rear wing was an obvious difference.
New rear wing for Sauber © XPB
Having run a V-shaped wing for much of the season so far, the new wing sports more of a 'w' profile. It's suspected the old 'v' wing was shaped to aid the drag reduction device tested over the winter, so the new wing is likely to be a more frequently used medium-downforce solution.
The change in profile across its span is both to make the most of the direction of the airflow approaching the wing and also to reduce the amount of downforce created at the wing tips to reduce to reduce the drag the wing creates.
Additionally, the trailing edge of the wing sports two v-shaped cut outs that help straighten the flow passing under the wing and prevent the flow spreading outwards.
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