Williams FW31

Car_name = Williams FW31 | Image = [[File:Nakajima 2009 Spain.jpg|260px]] | Category = Formula One Constructor = Williams | Designer = Sam Michael (Technical Director) Ed Wood (Chief Designer) Clive Cooper (Head of Design - Composites and Structures) Christopher Brawn (Head of Design - Suspension, Steering, Breaks) Mark Loasby (Head of Design - Systems) Jon Tomlinson (Chief Aerodynamicist) Enrico Balbo (Double Diffuser, Concept Lead) | Predecessor = Williams FW30 | Successor = Williams FW32 | Team = AT&T Williams | Drivers = 16. Germany Nico Rosberg 17. Japan Kazuki Nakajima | Technical ref = | Chassis = Carbon-aramid and honeycomb composite monocoque. | Front suspension = Carbon fibre double wishbone, with pushrod activated springs. Zero keel geometry. | Rear suspension = Double wishbone, with pushrod activated springs. | Wheelbase = 3100 mm | Track = | Engine name = Toyota RVX-09 | Capacity = 2.4 L | Configuration = 90° V8. Limited to 18,000 rpm. | Turbo/NA = naturally-aspirated, | Engine position = longitudinally mid-mounted. | Power = 740 hp @ 18,000 rpm | Gearbox name = Williams | Gears = 7-speed | Type = electro-hydraulically actuated, semi-automatic, seamless shift. | Differential = | Weight = 605 kg (including driver) | Fuel = Esso | Lubricants = Mobil 1 | Tyres = Bridgestone Potenza | Debut = 2009 Australian Grand Prix Races = 17 | Wins = 0 | Cons_champ = | Drivers_champ = | Poles = 0 | Fastest_laps = 1 | Podiums = 0 The Williams FW31 was a Formula One motor racing car, designed and built by Williams F1. The AT&T Williams team used the FW31 to compete in the 2009 Formula One season. The car was unveiled on 19 January 2009 at the Autódromo Internacional do Algarve circuit in southern Portugal, and was first driven by the team's test driver Nico Hülkenberg. It was a mid-field runner, in contention for points on many occasions when driven by Rosberg, but rarely contending for podiums. Rosberg could have finished in third position at Marina Bay during the 2009 Singapore Grand Prix if he had not run wide on the exit of the pit lane and received a penalty.

Rosberg was criticised for failing to achieve a pole position while topping the times in practices on numerous occasions, notably at the 2009 Brazilian Grand Prix - the Williams cars had excelled during practice sessions in wet conditions, but did not produce the same level of performance in qualifying. While Rosberg often scored points, and elevated the car to a finishing position that it was considered incapable of, Nakajima failed to score a point all season and possibly cost the team a higher position in the championship standings than the seventh place they eventually achieved.

The Williams FW31 was the first British F1 car to use Esso-branded fuel since 1973, as well as the first Williams F1 car to use Mobil 1 lubricants since 1988 season, as they had been using ExxonMobil brands since 1999.

Diffuser controversy

At the first race of the season, an official complaint was launched by other teams against the rear diffusers of the Williams FW31, Toyota TF109 and the Brawn BGP 001 saying that they were illegal, but after analysing the cars, the FIA reported that the cars were not illegal. The teams appealed and after much deliberating the car were deemed legal by the FIA.