Given that the FIA declared Caterham's exhaust vane and Williams' exhaust bridge illegal, both teams have opted to back out of the option and not risk being disqualified at the Australian GP, the first race of the season where cars will be fully checked on their compliance with the technical regulations. Both teams simple bolted different parts on their cars, knowing that for both the CT03 as well as the FW35 the contested items were easily removable.

The image clearly shows the lack of vane on the Caterham, while also showing burning marks on the car's bodywork due to the internal components heating up the carbon fibre and its paint.

Williams technical director Mike Coughlan has clearly been looking near the boundaries of the regulations to find ever more performance while designing the FW35. Today at Barcelona the car appeared with open wheel nuts, contrary to the traditional pointy ones as can be seen in the inset.

By using wheel nuts, which are btw integrated into the new Rays magnesium alloy wheels, the team can push air through the hollow wheel axle. This means that part of the air caught by the brake ducts is fed into the axle and subsequently exits outboard of the wheel, along with more hot air from the brakes coming through the rim. As ever it will be matter of compromise for Williams to determine if it is worth it to have larger brake ducts in favour or getting more flow through the wheels. Larger brake ducts will increase drag, but more flow could help the team control the wake that is created behind the wheels, creating a big impact on the efficiency of the car's floor and diffuser.

Williams and Caterham have created a stir during winter testing as both the Williams FW35 and the earlier launched Caterham CT03 feature elements within the exhaust channels. In both cases, the exhaust tailpipe exits into a channel that is part of the sidepod's aerodynamic shell. The channel is designed in a manner that exhaust gases are curved down towards the car's floor as much as possible. Such exhausts, named Coanda according to the identically named principle that a fluid (in this case the exhaust gas) tends to be attracted to a nearby surface (in this case the downward sloping, U-shaped exhaust channel. It would of course be much easier to point the exhaust pipes downward and extend them further towards the diffuser, but that was banned when the FIA tried to eliminate the use of exhaust gases for aerodynamic purposes.

The issue now is that there is discussion about whether these two particular designs comply with article 5.8.4 of the FIA technical regulations. This defines a cone behind the exhaust tailpipes where it is not allowed to have any kind of bodywork.

In the case of Caterham's design, their exhaust channel with internal vane can only possibly comply with this rule if the turning vane is underneath the 'exhaust cone' as defined above. It seems however that this is not the case, as the FIA has apparently contacted Caterham to note that it believes the design is not allowed.

The Williams solution is even more interesting, as they have an 'open bridge' over the exhaust channel which attempts to bend exhaust gases down. While the small spacer in the middle of the bridge may possibly make this design legal, again, the FIA thinks otherwise as Williams was approached as well with the exact same message.

Both teams however stand firm that their designs are legal, but it will be interesting to see how long they will hold on to the solutions, or perhaps immediately not take the risk and test with a more conventional channel.

Already at the US GP in Austin 7 days ago, Mercedes AMG surprised by fitting Nico Rosberg's car with the old exhaust solution, favouring it over the Coanda solution that the team development following the example of McLaren. In Austin, the team wanted to do a direct on-track comparison to see the benefits and disadvantages of the Coanda exhaust solution. It is no secret that ever since its introduction, the team failed to get it to work properly, while the downwash of the exhaust gases also heat up the rear tyres.

Now in Brazil, with tyre warmup not a problem like in chilly Texas, both cars have the old exhaust layout. Norbert Haug mentioned that this option was chosen to be able to do a proper tyre test, comparing the car at the beginning of the season with that at the end. Although not mentioned by Haug, Pirelli also brought 2013 prototype tyres to Interlagos, something that Mercedes undoubtedly wanted to try out without having to work out how the Coanda exhaust influenced the test data.

The team is however focused to fit its 2013 car with a Coanda style exhaust, as Haug mentioned: "But it is very clear that you have to have Coanda next year, because it gives you a benefit." The first problem for Mercedes is of course trying to resolve their extremely high tyre wear which almost no team can match. In fact, in Austin, the team simultaneously struggled to get its tyres warmed up while also suffering from high thermal degradation.

McLaren have made a fairly major change in front wing design with their newest iteration introduced at the American GP in Austin. The new design drops a few McLaren-only styling elements, such as the sharp steps in the wing's main plane, as well as removing the r-winglet.

Generally speaking, the new design, and particularly the items that were changed appear to be inspired on Lotus F1's front wing. Therefore, the new wing features curves in the main plane, leading to a very different connection of the wing's elements to the endplate. There, the seperate downforce generating panels now curve down onto the floor plate of the endplate as seen with several others teams as well. The change will help manage airflow around the front wheels, and hopefully gain downforce that was dropped at the front by removing the r-winglet in favour of the new vertical flow conditioner - which will obviously create no downforce for the front wing itself.

As announced earlier this week, Lotus F1 have finally introduced their new Coanda style exhaust on the E20. It was tested by Kimi Raikkonen only during FP1 at the Korean International Circuit.

The layout very much resembles that of McLaren's downwash exhaust, however on the Lotus it does feature only a very minor bulge, instead the exhaust channel is almost seemlessly integrated into an unchanged sidepod shape. Another interesting detail is the metallic channel used by the team instead of special coated carbon fibre that other teams are using for weight benefits.

Also interesting is that the team are still not in need to extra cooling of the exhaust. Apart from two gills above the frontal upper suspension arm of the rear wheel, not additional outlets have been added - contrary to Ferrari, McLaren and Mercedes who all added gills around the exhaust at the time of introduction of their Coanda exhausts.

Although subtle, McLaren have introduced a minor change on the car. The winglet, just above the radiator air inlet, is effectively a connection between the sidepod panel and the monocoque.

The new winglet is a positioned a little higher above the sidepod aims to control airflow just above the sidepod, a crucial area to ensure efficiency of the downwash exhaust.

Red Bull introduced a considerable number of changes on its car at Singapore, including a new front wing, diffuser and DDRS. Perhaps of a little less importance, but still interesting is their new nose cone. Just like Williams did, the new nose has a slight bulge below the nose, in the middle of the nose but just behind the front wing pillars. Overall the tip of the nose on the Red Bull is also slightly lower, resulting in more airflow over the nose and less under it.

Such change is remarkable, especially because the currently nearly maximum-height noses of current F1 cars are all focused to get as much air as possible under the nose and towards the floor. It is of course part of Red Bull's changes to improve the balance of the RB8. Adrian Newey mentioned before the Japanese GP that "the team have been focusing mainly on restoring the car's balance after losing the effect of the exhaust blown diffusers that we had for the past two years".

Ferrari is more and more struggling to keep up with the development pace of other teams, with Singapore being no exception. The team brought a new rear wing featuring interesting changes, but after testing both the new and the previous wing on Friday by applying flow-vis paint, the Italians opted to use the older version on both cars as the new one did not bring the improvement the team had hoped for.

The new wing features a lot more slots in the endplate (the old wing is displayed in the inset), extending onto the rear wing's flap. The idea of this is to reduce the strength of the vortex coming off of the endplate, reducing the drag from the wing assembly. To help with this, the cut-out at the top of the endplates, just behind the flap is also more pronounced.

On the lower end of the endplates, 8 vanes now work in combination with the diffuser, attempting to extract as much air to the outside of the vanes, hence trying to speed up the flow in between both endplates.

While a single wing may not be a problem, Ferrari do have a serious problem on their hand, as they have already failed numerous times this season to get their car updates to work effectively. The team for instance had a considerably different front wing at Valencia, but after 3 consecutive Fridays of testing finally decided not to use it.

Another change, a number of winglets attached to the barge boards were seen at Hungary, but never again. Given the high downforce nature of the track, one could have expected to see this item return at Singapore, but that was not the case.

All in all, the problems are creating trouble at Ferrari, with Alonso now openly expressing his worries about Ferrari's development progress. Domenicali and Fry also immediately left Singapore after the race to return to Marcello as soon as possible to oversee further developments for the remaining races of the season. Under their self dubbed “less haste, more speed,” the engineers at Maranello are now hard at work to try to solve the problems which are likely to be correlation issues with the wind tunnel.

Ever since their famous exhaust updates where the team brought several different versions to test on the track, development has not gone like the team would have liked. Some updates have worked, but those that don't are costly in the race for the championship.

Red Bull Racing debuted a new front wing on the RB8, featuring two changes. The first of which is the addition of an extra slot where the front wing is ahead of the wheels. This means a little bit more air will reach the underside of the flap, filling the low pressure area underneath the front wing. Although this can add downforce at the front, its most important function is likely to be better control of the airflow around the front wheel, hence the front wheel's wake and underneath the car's floor.

Secondly, the upper flap was split up into two panels where that flap is not ahead of the wheels. This is again a change that effects the car's aerodynamic performance further downstream. Having two panels instead of one means there are two ends, hence also two less strong vortices coming off the inside tip of the flaps, instead of a single, stronger one in the previous design.