The MP4/25 had its rear axle upper winglets modified at Turkey . They have now a more horizontal profile compared to the old inclined upwards profile . This change may have been triggered by the introduction of the new sidepod panels also for Turkey .
The major role of the rear axle winglets is to decrease turbulence in this zone created by rear wheel rotation and are considered by rules to be part of the braking system .
The new diffuser first tested at Silverstone alongside with the new exhaust blown diffuser package , has a new more boxy central zone with a new hole to access the engine starter , much shorter side walls and a curving downwards upper element to cope better with the new blown diffuser philosophy ( changes in orange color) .
Under the diffuser and on the inner large wall surface we can observe blue colored stripes . That is because the diffuser is coated with new heat protective paint to prevent shape deformation observed during free runs at Silverstone .
At Turkey the central zone twin fences have a new thicker upper part while the pointy side tabs were once again revised on a constant seek for the ideal flow of air through this zone ( all changes in orange color )
At Monaco an increase in height to the pointy extension’s tab fence took place ( in orange color ) .
The new diffuser ala “Renault “ style which was deployed at Catalunya had a completely new inner holed structure , an additional winglet under the light to aid air extraction from under the car , a new shaped central zone and additional central flaps .
The modified diffuser spec used at Sepang had smaller tabs (1) to increase slightly the pressure on the sunction side and a redesigned side pointy extension (2) to offer a better air circulation close to the inner rear wheel zone .
Following a rule ( article 3.12.7. ) clarification from FIA stewards at Bahrain Mc Laren at Melbourne had to decrease the motor access hole ( apart from the front wing’s sharp endplates ) , located at the central zone .
FIA REGULATIONS ABOUT MOTOR ACCESS HOLE
No bodywork which is visible from beneath the car and which lies between the rear wheel centre line and a point 350mm rearward of it may be more than 175mm above the reference plane. Any intersection of the surfaces in this area with a lateral or longitudinal vertical plane should form one continuous line which is visible from beneath the car. A single break in the surface is permitted solely to allow the minimum required access for the device referred to in Article 5.15.
In plain words Mc Laren run a larger than needed hole to access the engine starter to make its diffuser act partially as a triple decked instead of two-decked , gaining extra downforce .