McLaren: Suzuka upgrades and design overview

McLaren have proven to be Red Bulls nearest competitor for most of the season. While not quite having the same raw pace as the RB7, the MP4-26 is as fast on race day and arguably can be easier on its tyres. Having started with two bold concepts the “U” shapes sidepods and the mysterious “Octopus” exhaust, the design had to be compromised to ditch the complex exhaust and revert to a Red Bull style outer blown diffuser. Leaving McLaren with a large amount of space under the gearbox, that was supposed to package the exhaust. This left the car with a higher rear CofG without the benefits of the exhaust to offset it. So it’s been remarkable that McLaren have been able to morph the initial concept into a race winning, Red Bull baiting package.
The pace of development never slows, So McLaren arrived at Suzuka with a new diffuser detail and another iteration of its Silverstone short-chord rear wing.

Following a lot of the rest of the paddock , McLaren added a diffuser flap across the top edge of the diffuser exit. The flaps profile only being broken by a large gurney flap under the rear crash structure. As already discussed in the Red Bull Monza diffuser article (http://scarbsf1.wordpress.com/2011/09/22/red-bull-monza-diffuser-analysis/), this flap is an evolution of the trailing edge gurney, used to create lower pressure aft of the diffuser for more downforce. McLaren can run such a large central gurney flap as it sits in a 15cm window in the bodywork rules that allow taller bodywork. Its also beneficial as the raised rear crash structure (for the “octopus” exhaust) allows a good airflow to pass underneath it towards the gurney.

Again we saw McLaren run the short chord DRS rear wing, allowing the team to use the DRS more frequently during qualifying runs. This wing has already been detailed in the blog (http://scarbsf1.wordpress.com/2011/07/14/mclaren-new-drs-rear-wing/).

Further down the car, we can see the rear brake duct cascade. Rules allow 12cm of bodywork inboard of the rear wheels, there is no stipulation that these function as brake cooling ducts, so teams exploit this for ever larger stacks of aerofoil sections to gain downforce directly acting upon the wheels.
McLaren have also altered their exhaust system over recent races, switching from a simple oval profile tail pipes, for pipes that pinch-in to form a nozzle at their exit. Also the detailing around the floor area varies by track, with more or less floor being cutaway around the exhaust exit. This alters the amount of exhaust flow passing beneath the floor to suit differing ride heights. As one of the functions of the EBD is to act to seal the diffuser, often likened to a virtual skirt. The high energy exhaust gas, prevents other airflow entering the diffuser, thus maintaining downforce.
Its no surprise given the proximity of the brake ducts to the exhaust outlets, that the lower stack of brake duct aerofoils are heat protected. No doubt some of the exhausts energy is used to drive airflow under the ducts to create more downforce.

McLaren use a split cooling outlet set up, rather than Red Bull who tend to focus all the outlet area into the large bulged exit high up on the engine cover. McLaren’s main outlets are the exit to the sidepods coke bottle shape. With outlet area to the side of, and above the gearbox. This is aided by 3-slotted louvers on the flanks of the sidepods.

Lastly McLarens unique sidepod design is clear to understand from this angle. The “U” pods create a path for the airflow passing over the centre of the car, to reach the rear wing relative unobstructed. Typically airflow closer to the cars centreline is cleaner and has more energy. This is why designers tend to use this airflow to feed the sidepods for cooling purposes. What McLaren have done is to compromise on the cooling efficiency for greater rear wing performance. The small fin inside the channel is used to create a vortex to main the airflows energy and direction through the channel.

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