Work on the cars, based on the firms Impreza and Lancer models, began in late 2010 after the FIA World Motor Sport Council gave the green light to a new ‘R4’specification. An R4 kit, homologated by the current Group N manufacturers, enhanced the performance of the two-litre turbo cars, bringing them in line with the normally aspirated Super 2000s. R4-kit classifications were homologated 1st of May 2011

More details of the kit are yet to be finalised by the FIA, but 2011’s R4s were stronger and lighter than the existing N4 models, with longer suspension travel and modifications to steering columns, dashboards and windows. Further power was unlocked by widening the mandatory 33mm turbo restrictor.

Production car World Rally Champion Armindo Araujo gave a glimpse of the R4s potential when he drove a Mitsubishi Lancer Evo X R4 prototype at 2010’s Monza Rally Show in Italy. His times were consistently in the top two or three of the S2000 class and he rounded off the event by beating all the S2000 cars to win the final stage of the event.

Japanese Subaru Technica International (STi) developed and homologated a R4-kit for Subaru Impreza WRX STi N-5714 and N-5732 rally cars. The R4-kit increases the competitiveness of the group-N Subaru Impreza WRX STi.
R4-kit further improves on the already fast group-N Subaru Impreza WRX STi´s performance and reliability. For example it reduces the car's weight by approximately 50 kilograms, has stronger lower bottom arms with uniball and also increases the car's suspension travel for smoother and accurate functionality.

For more technical specifications regarding the R4-kit go to our downloads section below.