A long article here, I apologise in advance. It's a technical half season report on the cars. It's a subs only article from Autosport so I can't copy the link, hence posting the article. And the pictures won't be there. But for the technically minded its a good insightful read. And even I could understand most of it 
It's a scarbs article.Thanks to a combination of a relatively stable set of regulations and the need to devote design resources to next year's substantially different rules, there has been a more muted rate of development than usual in Formula 1 this season.
But despite this, there have been plenty of interesting technical development trends running through the season.
With budgets already tight for many teams, choosing where to spend money is a tough task. But offsetting the stability of the rules, with only a few subtle changes including the introduction of the optional vanity panel to shroud the step in the nose, was the major change in tyres - meaning teams have spent more time working with the rubber than pressing on with aerodynamic developments.
With 2014 on the horizon, many teams' packages for Monza and parts currently in development will be the last upgrades for this year to be signed off.
Those at the sharp end cannot afford to back off completely with so many races remaining and they must somehow balance the needs of 2013 and '14.
Some elements of development will be carried over, but the most significant area, the exhaust and Coanda sidepods, will not be allowed next year so any changes here will be solely focused on this year.
NOSES
Most teams have opted to fit the non-structural vanity panels over their stepped noses.
Mercedes altered its nose mid-season, while Caterham ran the 2012 nose until the major upgrade was introduced at Barcelona. While very obvious visually, the gains from the shape of the top of the nose are minimal and the underside is a much more rewarding avenue for development.
Lotus's nose © XPB
Firstly, the pylon joining the front wing to the nose is a useful means of altering the airflow. Most teams have extended these pylons into elongated vane line shapes, with Mercedes and McLaren the most recent to stretch their length.
Between these pylons another trend has been gaining popularity: the chin or 'pregnant' nose. This is a rounded bump under the nose that adds a small amount of downforce but little drag.
It speeds up airflow through the duct formed by the nose, pylons and front wing. This faster airflow reduces pressure under the nose and hence creates downforce.
As this area under the nose is so similar across all the cars, most teams are finding a small gain by adding this chin.
Development in this area will have relatively little long-term pay off as for 2014 the nose tip will be far lower. While the rules allow vanity panels and chins, the geometry of the nose will not reward these designs so much.
SIDEPODS
There were no rule changes relating to the exhausts for 2013, meaning teams have focused on making the most of the aerodynamic effect of the exhaust plume.
Even though the 2012 regulations raised the exhausts clear of the floor and enforced severe restrictions on engine mapping, this remains one of the most powerful aero devices on the car.
Via a mix of aerodynamic effects, the exhaust plume, which points upwards thanks to the rules dictating the direction of the pipe exits, is curved back downwards to blow alongside the edge of the diffuser. This helps to seal the edges of the diffuser, reducing leakage and the turbulence caused by the rear tyre.
Red Bull sidepods © XPB
Re-routing the exhaust flow is achieved largely through two different design solutions. The simpler solution is the one McLaren came up with in 2012, where the exhausts exit through a bulge in the sidepod. A short, curved ramp inside the bulge diverts flow downward via the Coanda effect and airflow passing over the top of the sidepod further bends the plume via a downwash effect.
This design still allows the normal airflow travelling around the sidepod to pass under the exhaust plume so as not to upset the car's conventional aerodynamics. This solution works quite well and appears to be less sensitive to exhaust flow and throttle position than other designs.
The second solution is Red Bull's tunnelled sidepod. Unique to Red bull in 2012, this year other teams have followed this route.
Lotus designed its car with this approach in mind and during the season, Sauber and Toro Rosso have evolved their take on the tunnelled sidepod.
This may be the more effective means of blowing the diffuser as the exhaust has a continuous section of bodywork to follow down to the diffuser's edge.
To allow the flow around the sidepod to reach the back of the car this ramped section has a tunnel underneath it. Rules limit the height and radius of the entry to this tunnel, so airflow has to be carefully managed through the small duct formed under the sidepod.
The tunnel exits around the centre of the diffuser and also produces a useful blowing effect on the starter motor hole. Although the ramped section may be more effective in blowing the diffuser, the restrictive tunnel does make this design more sensitive to throttle position.
The new rules will demand a single exhaust pipe from the diffuser that exits high up above the rear crash structure. It won't be possible to effectively blow the diffuser with the tail pipe in this area, although some rear wing blowing might be achievable.
With the loss of Coanda sidepods teams will lose some 60 points of downforce, which equates to around two seconds a lap, although they will regain some of this loss with development in other areas.
Aiding the Coanda and downwash effects over the exhaust plume are vortices created by various aero devices fitted around the front of the sidepod. Being small but quite influential parts, these are a cost-effective area of development.
Sauber's tunnelled sidepods © XPB
The solutions seem to be split into fins and vanes. Fins on the front shoulders of the sidepods or by the rear view mirrors will produce a spiralling vortex that diverts higher-energy airflow to area over the exhaust outlet and diffuser. Teams are increasing the effect of these fins by multiplying them. Williams and McLaren have run up to four fins on the front of their sidepods!
The other solution is to create a downwash with a horizontal vane. Sauber brought this idea to the sport last year and several teams have placed horizontal vanes over all or part of their sidepods.
Most recently, in Hungary, Red Bull created a hybrid device. This was a short fin extending sideways from the cockpit over the sidepod to create both a downwash and a vortex to improve flow over specific regions at the back of the car.
SUSPENSION
Due to teams' secrecy and the limited visibility of much of the car, most development that gets reported on is aerodynamic. But beneath the skin there's been a quiet revolution in suspension design over the past four years.
Ever since active suspension was banned in 1994, teams have had to find mechanical solutions to make the suspension work at its best at high speed and low speed. Until 2009 this meant using springs and roll bars, with clever linkages and dampers.
The limitation of this technology is that the front suspension is disconnected from the rear, so one end diving under braking or from suspension compression at high speed cannot not be compensated by the other end. With cars running ever-increasing rake, the front splitter (T-Tray) is getting closer to the track and risks wearing out the legality plank.
Lotus was probably the first team to link the front and rear suspension hydraulically in 2009, when known as Renault. Its PPH system was simple, but gave useful gains in preventing front ride height reducing at speed or under braking. This allowed softer springs for better grip at low speeds, but still provided stiffness for aerodynamic stability at high speed.
Mercedes introduced the FRIC system © XPB
It was well-publicised this year that Mercedes was running a more complicated system called FRIC (front rear inter connected) on the W04. This system has been on the car since at least 2011.
It not only links the suspension front-to-rear, but also left-to-right in roll. Its system added stiffness to the conventional springs in certain conditions to maintain ride height and again still provide a soft set-up for low-speed grip.
Most of the top teams run the Lotus style front-to-rear system, with Force India and Caterham introducing their own versions this year. But Lotus is believed to have evolved its simple system towards the complexity of Mercedes. The tell-tale sign is the hydraulic accumulator mounted in the left hand sidepod which is far larger now than it was earlier in the season.
Teams are investing large amounts of money in these concepts. Even with the far-reaching rule changes for 2014, this area of development will still carry over into next year and beyond.
This has brought some technical directors to suggest the return of active suspension. If controlled by the FIA SECU then this might be a cheaper way to achieve the same results for less money, as the cars and teams already have the skill and hardware to implement active suspension control.
FRONT WINGS
Front wings have become even more complex © XPB
A consensus appears to have been reached on front wing design regarding multiple-element outer sections and a variety of vanes and cascade winglets.
While the wing obviously adds to front downforce, it also increasingly plays a far larger role in managing the front tyre wake and the airflow back to the rear of the car. Indeed, most of the complexity of front wing design achieves these latter aims, rather than simply producing downforce.
Most teams have an outer wing span that starts as one or two elements and then splits into as many as seven elements near the endplate. The endplate area is now very three-dimensional, with the shape itself formed by the wings' main profile curling down to the footplate area.
This means the wing is producing an upwash and an outwash, with the latter flow passing around the tyre. This offsets the turbulence created by the tyre at ground level, which would otherwise pass back along the car and wreck the rear-end aerodynamics.
Above the main wing are various cascade vanes and winglets. These are all aimed at sending airflow and vortices around the front tyre, again to offset the turbulent wake it produces and to reduce the low pressure region behind the tyre that adds to the car's drag.
A lot of the work around the front wing is about the detail and each team finds slightly different solutions.
McLaren's front wing © XPB
While Lotus is one of the leading exponents of this, both Red Bull and Force India have introduced a new idea of shark teeth on the wing's main profile in order to manage front tyre wake.
For 2014 the front wing will be narrower by 7.5cm at each end. This won't make the wings as narrow as they were before 2009, but a decision will need to be made as to whether the wing sweeps in between the front wheels or, as currently, out around the wheel.
With the gains from managing front tyre wake overpowering the need for downforce, I suspect that the outwash design will continue to be the direction of choice. That means a lot of current wing development will be transferable to next year.
REAR WINGS
When Ferrari launched its F138 with an array of vertical vanes on the trailing edge of the rear wing endplate, I suspected this would be a much-copied design direction.
But it is the slot on the leading edge of the endplate that has become de rigueur for the teams in recent races.
The slot in rear wing slot has become standard © XPB
This simple slot takes airflow from outside the rear wing and passes it inside the endplate. This allows more flow to pass through the rear wing, lowering pressure and increasing downforce.
Ferrari, Red Bull and McLaren have adopted this slot, taking ideas from the midfield teams that introduced it last year.
At higher-downforce tracks Lotus and Red Bull have also found a new loophole that allows a small additional rear wing profile to be used.
There is an area low down, beneath the beam wing, where an aerofoil profile can be used.
This works like a leading-edge strake ahead of the beam wing, increasing the wing's ability to create downforce.
PASSIVE DRAG REDUCTION SYSTEM
At Silverstone, Lotus raced its passive drag reduction device for the first time. This is a passive F-duct type solution, which stalls the rear wing at high speed.
Unlike the F-duct or last year's double DRS however the system is only operated by airspeed, not by the driver or the DRS mechanism, making it legal.
By opening up the 'ears' that have been mounted to the roll-hoop all year, high-pressure air is fed into a system of ducts. At low speed, the airflow passes straight through a large duct exiting over the rear beam wing.
At higher speeds though a control duct linked to the engine airbox inlet redirects the airflow to the duct exiting under the top rear wing.
The Lotus passive drag reduction © XPB
As air blows out of the slots in the duct, it breaks up the airflow under the wing and cause it to stall. This reduces downforce and drag, allowing a higher top speed.
Lotus is believed to be able to gain 8mph from their system, although it is more likely to run more wing for faster cornering and stall the wing to achieve the same top speed as the standard car.
This device has been over a year in testing. One of the main problems has been the rear wing stalling at the wrong time, either due to air leaking under the wing or due to obstruction of the duct under the wing.
Detail development led to small outlets in the rear wing duct bleeding airflow at lower speeds, but when Lotus followed Mercedes' idea it had the rear wing duct spaced away from the wing's surface, blowing upward under the wing to stall it.
This system is likely to be reintroduced in upcoming races: Sauber and Mercedes have both tested a similar configuration in the past and could introduce them in the near future.
These systems will remain in 2014 as the FIA have not expressly banned their design.
The packaging of the system around the new powertrain could however make their installation more difficult.
BRAKE DUCTS
Since Pirelli introduced its hotter-running, higher degradation tyres last year, teams have sought to find ways to keep the tyre in its working temperature range.
One way is to use the heat from the brakes. The discs run at 900-degrees Centrigrade and this heat can pass into the wheel and hence the tyre.
Teams will either try to duct more, or less, brake heat into the wheel depending on their tyre situation.
McLaren even tried adjustable ducts last year, which allowed mechanics to alter the brake/tyre heat transfer at pitstops.
Teams are using heat from the brakes to help tyre temperature © XPB
This year teams have fitted different brake duct drums, which either open up the brake disc to the wheel or cover it up and exit straight out of the wheel.
In Hungary, there was a suggestion that Mercedes was running rear wheels featuring rims with a 'double wall' design.
A black shadow was visible just inside the rim's inner edge, which suggested Mercedes was perhaps trying to insulate the rear tyres from the brakes in order to ease its tyre degradation problems.
While this seemed to be a valid idea, there are several factors that would prevent the solution working - namely the complications of making tyres fit around a bigger wheel and homologation rules.
But the answer to the mysterious back ring inside the wheel is simple: teams try to seal the gap between the brake duct and wheel rim, with very small tolerances.
The wheel will flex under load and the duct can rub on the rim, causing heat and wear to both parts.
On the front brake ducts, where the shape is simpler, the teams fit a friction-reducing tape to the duct to help seal and prevent rubbing.
On the rear, the brake shape is more complex so the friction reduction seal is fitted to the wheel. Being black it was mistaken for a hole, prompting the Internet rumours.
Last year Red Bull had its blown wheelnut/axle design banned at Monaco. But this year, Williams introduced a legal reinterpretation of the idea.
This version works by blowing air out through the wheelnut. The additional airflow passing through the wheel is also beneficial for combating the troublesome front tyre wake.
Although the axles are hollow anyway, engineering a blown system does compromise the design, not least the axle lacking the pointed end to aid wheel fitting at pitstops
Wheelnuts are getting more sophisticated © XPB
It is not surprising that Williams dropped this blown axle design for a more conventional set up following the pitlane accident at the German GP and subsequent FIA rules and penalties on pitstop errors.
Other teams have similar means to pass air through the wheel for aero rather than cooling purposes.
Most teams will have what outwardly appear to be cooling ducts around the brakes, but which are actually designed to pass air out through the wheel without ever reaching any part of the brakes.
These act in the same way as the blown wheel nut and simply vent more air out through the wheel, influencing the ground vortices shed by the rotating front wheel.
Similarly with the rear brakes teams are now venting some of the hot air from the brakes out through the inner face of the wheel.
This is contrary to the usual method of passing hot air out of the outer face of the wheel, but again the duct work is legal and is used to create some aerodynamic gains in area where bodywork is restricted and the tyre turbulence upsets the airflow.
With the rules on pitlane penalties remaining, and no rule changes around the brake ducts or wheels, this is likely to be an area of greater development in 2014.
Le coeur a ses raisons que la raison ne connaît point. 
