The double diffuser

Brawn BGP 001 2009 double diffuser detail view

Photo by: Giorgio Piola

Firstly, let’s wind it back to 2009, a turbulent period which had seen Honda quit F1 amid the global financial crisis at the end of the previous season. His works outfit was subject to a management buyout that resulted in Ross Brawn’s name being emblazoned across the car and the team.

Honda had spent a considerable amount of money on the incoming regulation change and, like Williams and Toyota, it happened upon a gray area in the regulations that led to the use of what was known became as a double deck diffuser arrangement.

The other teams quickly realized this was providing a significant performance advantage and either had to prevent its use, in order to peg back Brawn GP, ​​which clearly had the best package to include it, or they had to develop their own version.

Most of the teams appeared to do this in tandem, with an early season protest lodged against the design. Its legality was to be decided at the FIA’s court of appeal and threatened the result of the first few races before it was given the all-clear.

Meanwhile, Brawn’s rivals worked in the background to design their own version of the double diffuser, should it be considered legal, in order it could be fitted to their cars in the aftermath.

The crux of the double diffuser design lay in how the regulations had been written, which only referenced a key area in question as when viewed from beneath, and allowed a hole to exist in the vertical floor transition.

This hole provided passage for the airflow into the diffuser’s separated upper deck, which allowed both segments of the diffuser to be designed with this in mind.

Not set up to originally accommodate this arrangement, some of the teams struggled to find the optimal design solution in 2009 and would have to wait until the following campaign to fully extract the available performance.

Red Bull had perhaps the toughest challenge in this respect, as the team had chosen to make the switch to a pull rod rear suspension layout at the rear of the RB5, making it more difficult to accommodate the floor openings and secondary diffuser deck design.

Blown floors

Red Bull RB6 exhausts

Red Bull RB6 exhausts

Photo by: Giorgio Piola

It was the diffuser that would be at the forefront of the development battle again in 2010 and, whilst the double decked arrangement could be used once again, it was the placement of the exhaust that would prove pivotal.

This time it was Red Bull which set the trend, even if it did try to disguise what it was up to when introducing the solution during pre-season testing.

It applied stickers to the RB5’s bodywork in a similar position to where its periscope exhaust had sat previously.

Not so obvious was the lowline exhaust it was introducing that could be found just above the floor and in a position to blow the exhaust gases between the tire and diffuser’s sidewalls.

The rest of the teams sat up and took note immediately, and set about introducing their own variant.

But, as always, when a team gets a head start on its rivals it can be difficult to make up the deficit. On this occasion, Red Bull worked diligently with Renault to maximize its advantage, with off throttle blowing becoming another string in its exhaust blowing bow that rivals would also have to copy.

The F-Duct

McLaren MP4-25 'F-duct' snorkel

McLaren MP4-25 ‘F-duct’ snorkel

Photo by: Giorgio Piola

The 2010 season proved to be an extreme development phase for F1, as the exhaust blown diffuser wasn’t the only interesting technical feature to grace the machinery that year.

McLaren introduced what would become known as the F-Duct, a driver controlled system that reduced drag at the rear wing when it was employed.

This allowed teams to run more downforce on the wing for cornering than it could ordinarily use, knowing the driver could deploy the F-duct on the straights.

It had its own internal designation within the team, but earned the F-Duct moniker owing to the fact that the signal duct on the front of the chassis was next to the F in Vodafone, McLaren’s title sponsor at that time.

The system was controlled by the driver when he covered a hole in the cockpit, which many assumed would be difficult to copy, not only due to the complexity of understanding the fluidic switch aspect but also because there would be challenges to be overcome in terms of incorporating the pipework within the confines of the cockpit and under the engine cover.

Ferrari F10 'F-Duct' driver activation pipework

Ferrari F10 ‘F-Duct’ driver activation pipework

Photo by: Giorgio Piola

In this respect, it became clear that the various solutions, owing to the placement of their pipework within the cockpit, required drivers to use different parts of their anatomy to close off the duct, with some even using modified gloves or sections of their race suits to fulfill that need.

As the drivers pushed the boundaries of when the F-duct was used, often steering one handed on the exit of corners, it became clear that the FIA ​​must step in.

The governing body closed the loopholes that had been allowed for the system’s introduction since 2011 onwards. However, this was not before realizing that what it had seen offered some advantages in terms of the racing spectacle, with DRS introduced to supplant the F-duct.

Coanda exhausts

McLaren MP4-27 semi 'Coanda' exhaust solution, gills added in front of rear suspension to reject heat

McLaren MP4-27 semi ‘Coanda’ exhaust solution, gills added in front of rear suspension to reject heat

Photo by: Giorgio Piola

The complexity of the exhaust blown diffuser solutions used during 2010 and 2011 had culminated in the FIA ​​preventing the use of off-throttle blowing, while also creating more narrowly defined positions for the exhaust outlet in 2012.

However, whilst the teams would no longer be able to channel the exhaust outlet into the desired location, they had no intention of simply relinquishing the performance advantage they had enjoyed over the course of the last few seasons.

And, as such, the ‘Coanda’ exhaustive solutions were born, with a number of variants employed by the teams as they looked to claw back some of the performance they had lost.

Two main contenders emerged and were developed extensively throughout the course of 2012, the semi-Coanda and the down ramp solution.

The semi-Coanda solution was first seen on the McLaren MP4-27, with a rear pod perched out over the top of floor that saw the exhaust plume drawn down into a similar area where the exhaust blown diffusers had been physically channeled.

This perched position above the floor also allowed the airflow that arrived around the side of the sidepod passageway into the coke bottle region (blue arrows, above).

Red Bull RB8 sidepod and exhaust changes (twin cross-under tunnel in new specification, old spec inset)
Red Bull RB8 exhaust solution change (older specification inset)

Meanwhile, the down ramp solution, seen on the Red Bull RB8, created a physical passage for the exhaust plume to follow into the desired location beside the diffuser and tire’s sidewall. However, this came at the expense of being able to better direct the airflow’s passage into the coke bottle region.

In an effort to better utilize the airflow and exhaust gases, which were competing for a similar space, Red Bull chose to run a cross under tunnel arrangement, which was relentlessly developed throughout the course of the season, with the shape of the trough in which the exhaust outlet exited also constantly under a state of flux.

Red Bull RB8 exhaust detail, note use of 'Helmholtz' resonance chamber (alterations made to original specification, inset)

Red Bull RB8 exhaust detail, note use of ‘Helmholtz’ resonance chamber (alterations made to original specification, inset)

Photo by: Giorgio Piola

To better tune the plume of exhaust gases emitted, given they’d lost the ability to blow the exhaust off throttle, teams also developed resonator chambers within the exhaust system.

YOU GIVE

Finally, one of the most bizarre visual technical novelties to appear during the course of a pre-season test came in 2020, when the onboard camera captured Lewis Hamilton pulling and pushing on the steering wheel of his Mercedes W11 like it was an aircraft’s yoke.

The unusual movement immediately prompted speculation as to what was being altered in the W11’s setup when the driver used what Mercedes had already coined as a Dual-Axis Steering system (DAS).

Mercedes AMG W11 DAS steering

Mercedes AMG W11 DAS steering

Photo by: Giorgio Piola

The driver would use DAS routinely around the course of a lap, with the system providing a different toe angle depending on the position of the wheel.

This essentially gave the driver more control over the car’s setup, on the fly, rather than having the conventional trade-off.

This adjustability likely allowed the team to run a more aggressive toe angle for cornering than would otherwise be possible, as the tread and bulk temperature of the tire wouldn’t skyrocket from the additional scrubbing that would ordinarily be caused on the straights.

The system’s life span was short lived, as the incoming regulations were changed for 2021 to prevent its use, which also put paid to anyone looking into developing a similar system for 2020, as the performance gains on offer didn’t seem to be enough to warrant the cost to develop it for what would be just a few races.



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