World Rally Car
A World Rally Car is a racing automobile built to the specific regulations set by the Fédération Internationale de l'Automobile and designed for competition in the World Rally Championship. The cars were introduced in 1997 as a replacement for Group A regulations used in the manufacturers' championship, and were replaced by Group Rally1 in 2022.
Regulations
1997–2010
Between 1997 and 2010, the regulations mandated that World Rally Cars must have been built upon a production car with a minimum production run of 2500 units. A number of modifications could be made including increasing the engine displacement up to 2.0L, forced induction, addition of four wheel drive, fitment of a sequential gearbox, modified suspension layout and attachment points, aerodynamic body modifications, weight reduction to a minimum of 1230 kg and chassis strengthening for greater rigidity. The maximum width was set at 1770 mm while front and rear tracks shouldn't exceed 1550 mm.Unlike the requirements for the preceding Group A cars, manufacturers were no longer required to build "homologation specials" in order to meet approval. The base model did not need to have all the characteristics of the WRC car, as evidenced from cars such the Peugeot 206, 307, Citroën Xsara, and Škoda Fabia, which during this period had no road car variant with a turbocharged petrol engine or four-wheel-drive.
To limit power, all forced induction cars were fitted with a 34 mm diameter air restrictor before the turbocharger inlet, limiting the airflow to about 10 cubic meters per minute. The restriction was intended to limit power output to although some WRC engines were believed to produce around. Engine development did not focus on peak power output but towards producing a very wide powerband. Typically, power output in excess of was available from 3000 rpm to the 7500 rpm maximum, with a peak of at around 5500 rpm. At 2000 rpm power output was slightly above.
By 2004, the best cars had ABS, electronic clutch control, paddle-shift, traction control, three active differentials, ride height control with GPS, electronic dampers and active suspension.
For 2005 the maximum width of the WRC cars was increased from 1770 mm to 1800 mm.
In an attempt to cut costs, since 2006 new regulations required mechanical front and rear differentials, while the central differential remained active. Active suspension and water injections were also prohibited. Cars entered by a manufacturer had to be equipped with the same engine for two rallies; further limitations were imposed on the changing of some parts, including suspension, steering, turbochargers, and gearboxes.
2011–2016
Starting in 2011, rules for WRC cars changed to be more restrictive. New regulations were derived from Super 2000 cars with a different aerodynamic kit. The cars could be smaller models.Exotic materials were forbidden except when present in the base model. Carbon fibre and aramid fibre were very restricted, except for bodywork's side protections where multiple layers of aramid fibre were allowed.
The gear changes must be made with a mechanical linkage system, so paddle-shifters were outlawed. However the system was re-allowed in 2015. There was no center differential, but the new regulation allows the only front and rear axle differential and a mechanical clutch to disconnect the rear axle during handbrake use. These two differentials must be mechanical, without electronic control or hydraulic or viscous systems.
The minimum weight was 1200 kg empty and 1350 kg with driver and co-driver.
2017–2021
The 1.6 L turbo-charged global race engine was retained in the 2017 World Rally Car regulations, but the turbo restrictor diameter was increased from 33 mm to 36 mm, increasing the engine's power output from. The minimum empty vehicle weight was decreased by 10 kg but the combined vehicle, crew and spare wheel weight remained at 1360 kg.Manufacturers were given more freedom to maximise aerodynamic performance, including large brake cooling ducts in fairings forming enlarged wheel arches. Electronically controlled active centre differentials were permitted, while the front and rear differentials remain mechanical.
While 2011 specification World Rally Cars were allowed to compete in 2017, the new World Rally Cars were allowed for use by manufacturers' teams only.