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SEAT Leon S2000's development
Ahead of the news that SEAT’s ultra-successful León Super 2000 touring car may be given a new lease of life in 2012, PMW presented an insider’s perspective on its development
by Jordi Riba and Graham Heeps
With Volkswagen having developed a 1.6-liter turbo race engine for its forthcoming Polo R WRC car, the possibility has arisen that SEAT may use the powerplant to make a limited return to customer motorsport in 2012.
The remarkable thing is that this would represent the fourth engine for the ubiquitous León, which started out with a 2-liter NA engine in 2005. It later became the first diesel-engined S2000, running a 2-liter TDI with great success, while in 2011, the SUNRED team fitted a Lehmann-built 1.6-turbo.
The diesel car was particularly challenging to develop.
“The first shakedown of the Leon TDi WTCC during the summer of 2007 confirmed what all the previsions had foreseen,” says Xavi Serra, SEAT Sport’s chief race engineer. “There was more power, but the quite neutral balance and good reactivity of the fun-to-drive petrol car, had become slow to react, with a notable change to an understeer balance.”
Several changes were made to counter this, including altering the positions of the movable ballast, extinguishers, etc. The front springs required a softer setting to take care of the Yokohama control tire, and the longitudinal pitch geometry was changed too. On the rear axle, different set-up options aimed for a softer load transfer on the rear axle, with an outer tire movement that helped to steer the car, since the front axle was close to the limit.
The changes required for the diesel led to a number of interesting technical features and test techniques being adopted by the SEAT Sport team.
A Beru TPMS system was introduced in the middle of 2008, mainly to avoid punctures, while tread temperature sensors from Texys were used both in race and test events, to control and evaluate the different setup changes and their effect on the rubber temperatures. Even a warning for cold tire temperatures was used during winter testing.
To prepare for the team’s first outing at Imola in 2008, the Sigma ECU’s real-time channels were used during a test run on a high-speed oval track to simulate the acceleration and braking processes, the main issue at Imola. These sent ‘what to do’ information to the driver’s display, with orders like ‘Push until 230km/h" and so on. A race distance was done using this process, to check the likely fading problems and other possible braking issues.
An Inertial Measurement Unit was used for the development of the 2009 car to analyze small improvements in the car’s balance, since it gave very precise data on the car's heading angle and attitude (roll and pitch), as well as being very useful to check very small differences in the driving lines between drivers.
Since all the setup information and logged data was openly shared within all the engineering staff of the team, the team used a website-based setup database to share the setups of all five works cars. This also gave the option to store some significant data to summarize each session, obtained either from the datalogging system or the meteorological station.
On top of the usual data analysis (via Toolbox), the team profited from its Data Object Wrapper license, which enables the user to ‘tap’ or pick up the desired data directly from the data file, without having to export. More detailed analysis can then be done in Excel or through some previously programmed interfaces in MATLAB. The team used this to keep track of damper performance and evaluate its damper setup changes, while also optimizing up-shift up points.
By the end of 2009, the team had started using Wi-Fi-based telemetry for testing. The equipment had previously been used to send engine maps without stopping the car; it was then expanded to receive data from both engine and chassis, reaching coverage values close to 99% at circuits such as Magny-Cours or Algarve. This was used for keeping control of the main chassis and engine values and also to send new engine maps as the car passed by the main straight.
For chassis development the team also used an instrumented arm (developed and patented by IDIADA, pictured) to measure the real positions and angles that the rear axle was experiencing under load on a skid-pad, in order to optimize its performance and help steer the front.
Regarding aerodynamics, few changes were made from the original petrol car, which had already been trough some Saint-Cyr and Ingolstadt wind tunnel sessions. The scale model was updated to diesel spec and run again in the Magny-Cours wind tunnel. The car had to accommodate both the intercooler and the radiator in a space that initially was conceived only for the latter, while also ensuring a good flow through the permitted opening on the bonnet. The airflow under the car was also optimized by the exhaust line and the fuel tank, once the initially mandated flat floor had to be removed.
On the damping side, the team used both Sachs and Öhlins (both of them four-way adjustable) depending on the track and also on new developments, taking advantage of the “development fight” that both suppliers had to face to stay on the list of available parts for the following race. Several handling tests were undertaken and also curb riding, since with the diesel there was a notable change in the mass you had to control, so special attention was paid to the landing after curb impacts. Damper performance was monitored using the team’s self-created MATLAB graphical interface, which was intended to act as a form of ‘dynamic shaker rig’.
As well as improvements to the standing start performance, a lot of emphasis during testing was also placed on the stopping performance. Some the three available test cars ran brake temperature sensors and most of the brake pads on the market were evaluated in deceleration, bite, ease of modulation and driver feedback. During a race weekend, the race engineer could then choose the most suitable pads depending on the circuit.
With such a wealth of development knowledge behind it and a huge amount of data available, not to mention an extremely well-sorted chassis, there’s no reason why the León S2000 shouldn’t be competitive again in 2012, as it enters its eighth season of world-class competition.