Lotus's DRS device explained

This weekend's German Grand Prix at Hockenheim has turned out to be a key point in the season's technical development. Having had time since the last major updates at the Spanish GP and with the summer break coming up, many teams have used the British and German GPs to bring their next raft of updates. After the rain-soaked practice cost them development time at Silverstone, the teams arrived in Germany with the determination to introduce more new parts.

Nearly every team has something new and in some cases the updates are major, such as McLaren's new sidepods. A lot of this development is teams converging on the ideas of others, such as Caterham's major aero update. But for Lotus, we have seen some real innovation with its new DRS ducts.

Lotus

In the run up to the German GP Lotus promised "interesting" updates. Accordingly Kimi Raikkonen's car was set up with different rear end aero parts to Romain Grosjean's. It's been immediately obvious that a new duct system has been added to the E20, with inlets around the roll hoop, a large duct exiting over the beam wing and a smaller duct passing up to the rear wing.

This appears to be a DRS activated system, which Lotus has simply called its 'prototype gadget'. We know that the origins of this system came from Lotus's unsuccessful protest against Mercedes Double DRS system earlier this year. With the Mercedes system being declared legal, Lotus is the first team to appear with a similar system.

Mercedes has raced its DDRS system, which uses the DRS rear wing to blow through ducts running the length of the car to stall the front wing, all year. This has several aero effects, which add up to less drag when DRS is open and hence more top speed. The Mercedes DDRS is itself is an idea inspired by McLaren F-Ducts of 2010. These systems used a driver operated 'fluid switch' to stall the rear wing at speed.

Whereas the driver-operated element of the F-Duct was outlawed, stalling wings for greater top speed was not. So the Mercedes DDRS took an interpretation of the rules, to find a secondary use for the DRS flap moving on the rear wing to activate the stalling of the front wing.

Just as the Mercedes DDRS was initially a bit of mystery, so too is the Lotus E20 DRS - until all the duct work is exposed. What we can see is a large diameter duct fed by scoops near the roll hoop. This exits the engine cover and passes over the beam wing. Then passing from this duct up to the rear wing is a smaller duct.

Aside from the visible duct work, much of the car's bodywork remains the same on both cars and to that raced at Silverstone. So the system may not even be complete, as perhaps suggested by the 'prototype' tag used by the team.

Somehow when the DRS rear wing flap is activated, the airflow through these ducts changes and creates a different aerodynamic effect. It's clear that this system is not like the Mercedes set-up and doesn't stall the front wing. Potentially the system could create more top speed by stalling the rear wing. Or, the missing/unseen ducting could be blowing the diffuser for more downforce when DRS is closed. Paddock rumour suggests the system works on the latter strategy, to boost downforce for low speed/high downforce tracks. However a tantalising prospect is that the system could be doing a bit of both, blowing the diffuser at low speed, then stalling the rear wing when DRS is open.

As this outing in Germany was simply a test to gather data, the E20 DRS was removed from Raikkonen's car for qualifying and will not therefore be raced. However the system is expected to see a return in future grands prix with a view to being raced.

McLaren

Whereas Lotus surprised most with the level of innovation, McLaren's pre-races comment about a big visual change appeared to lead to much simpler developments. McLaren has added a major revision of the sidepod/exhaust set-up to the Silverstone upgrade (front wing, floor and brake ducts).

This year McLaren has stolen a march on the rest of the grid with the MP4/27's exhaust set-up. Its exhaust exits sideways through a duct in a bulged exhaust fairing. The exhaust follows the down curve of the duct and the downwash airflow over the sidepod, which all conspires to redirect exhaust flow to point downwards. This legally blows the edge of the diffuser for an effect similar to last year's blown diffusers. The effect is not as efficient as the low mounted exhausts seen last year, but is about as much as you can recover with this year's rules demanding higher exhausts pointing upwards.

In the first half of the season many teams have followed McLaren's style of exhaust set-up: Ferrari, Sauber, Force India, Williams, Toro Rosso and Caterham. Now McLaren has made its first update to the sidepod/exhaust set-up since the start of the season. Its new sidepods are smoother, with the exhaust fairing now less of a bulge, but merged more seamlessly into the sidepod shape.

Perhaps more importantly the undercut shape of the sidepods is now more pronounced, the internal packaging of the electronics radiators and ducting of the sidepods have been altered to allow a deeper undercut. This allows more airflow to pass under the exhaust bulge and reach the diffuser. This increases airflow over the diffuser for more downforce. Despite the changes to the sidepod shape, Sam Michael confirmed the car has not needed new side impact crash tests.

McLaren's new sidepods © XPB

Along with the general sidepod shape, the bodywork has gained new fins on the front shoulders of the sidepod. Whereas two fins first appeared on the car earlier this year, the German GP spec ups the fin count to three. These fins set up a series of trailing vortices along the top of the sidepods to direct airflow most effectively over the exhaust outlet. This helps redirect the exhaust plume towards the diffuser. Although the effect of the vortices over the top of the sidepod creates lift, the net effect with the extra created by exhaust on the diffuser means more total downforce.

The changes in Germany were part of a general aero programme to add more downforce. They weren't specifically aimed at the problems Jenson Button has suffered with the cars set up and Pirelli tyre management. However, in the dry practice sessions at least, these changes appear to have brought both McLaren drivers up to the speed of their rivals.

General technical developments

Ferrari and Red Bull had new front wings and further sidepod revisions at Silverstone. These parts have been carried over to Hockenheim, although Ferrari has yet to race its new 'extreme' front wing. This wing focuses the downforce it creates towards the outer tips, a series of wing profiles curve outwards to direct the wings wake around the outside of the front tyre. In some places the wing is formed of seven separate profiles, which when added to the cascade winglet above the main wing, means nine elements are used in total! Along with its shark tooth bargeboard tips, Ferrari is clearly getting more adventurous with their aero development.

Both Ferrari and Red Bull have added a resonant Helmholtz chamber to the exhaust system. This extra closed end of tube running from the exhaust system aids mid-range power, by altering the tuned length of the exhaust at certain RPM. It's also possible it has a legal smoothing effect on the exhaust flow when the driver is on and off the throttle.

Williams introduced a revised front wing © XPB

Williams also has a new front wing with detail changes to the cascade winglets and the flap design. The wing was also tested at Silverstone and finally made it into qualifying for Germany. Although the McLaren style sidepod/exhausts remain tested, but unraced.

Caterham brought a huge range of updated parts to Silverstone and these were applied to both cars at the British race, with further updates in Germany. The CT01's main updates are McLaren style sidepod and exhausts, as well as revisions to the brake ducts, turning vanes and front wing.

Not to be outdone by Caterham, Marussia introduced its first windtunnel developed parts, with a revised nose, rear wing and turning vanes. In a year of where high stepped noses have been prominent, the MR01's lower nose gained an aerodynamic 'chin' to help produce downforce in the middle section of wing.