rallies since 2019 but the FIA regional rally championships continue to allow N4 cars. Away from FIA sanctioned events, many rallies at national level are run under Group N. Some local variants of Group N have been created to allow other marques to compete where Group N is the national formula. Allowed modifications The range of modifications allowed was quite narrow - few mechanical engine modifications were allowed (save for lightening within set limits and baffled sumps) although the choice of ECU was free, and this could liberate some extra power itself, and most of the modifications allowed were to promote longevity rather than increased performance, although the boundaries of these two areas were blurring towards the end of the group's lifespan. Furthermore, cars with forced induction engines were fitted with a restrictor in front of the charger to limit power. Originally, Group N meant that all the interior trim had to be present (including the rear seat), but it later changed to allow removal of the trim aside from the dashboard and replacement of the door trim. The springs and dampers were free, as are the internals of the gearbox and the final-drive ratio, providing that the homologated gear ratios and gear change pattern were respected. This allowed the use of dog-engagement gearboxes, providing quicker gearchanges and longer gearbox life. There was provision for strengthening of the suspension components and bodyshell, provided this didn't alter the operating principle. References Group N Touring car racing Fédération Internationale de l'Automobile Rally groups Racing car classes