Group N (otherwise known as NR4 as of 2018) was introduced in the 1980s as a replacement for the Group 1 (standard touring cars) class, allowing little if any modifications to the cars. With so many restrictions and a daunting homologation requirement (a minimum of 2500 cars of the competing model had to be built in one year, out of 25,000 for the entire range of the model), the Group N class can be considered as the entry level class for beginners getting into rallying, using only production based cars with little (if any) modifications to increase performance. in 2013 the class was renamed to Group R, however that class was later phased out and replaced with the NR4 class. Both Group R and NR4 are essentially the same as Group N. videos more information (https://en.wikipedia.org/wiki/Group_N)
