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GP Week : Issue 126
WRC PREVIEW >> New in the 2011 rally season are the Group R4 rally cars, conversions of cars running under the old N4 Class. The intention is to make the traditional turbocharged Mitsubishi and Subaru cars more competitive with the old generation and much more expensive 2-litre normally aspirated Super 2000 cars. Until the end of 2009, the N4 class cars ran with a 32mm restrictor, but there was a marked performance shortfall over many conditions found round the world, so at the start of the 2010 season the differential was reduced when 33mm restrictors were permitted, but still there was a general shortfall. More radical modifications were required, especially as the two types of car ran together under the same old class system. Meanwhile at the start of the 2011 season the FIA changed the class systems, so that now the old N4 specification cars would run alone in the new Class 3, the cars modified into the new R4 rules would run in Class 2 together with old generation Super 2000 cars, while the new generation (1.6 turbo, direct injection) Super 2000s would run alone in Class 1. Neste Oil Rally Finland will see the first time that the Mitsubishi and the Subaru R4 cars face each other in the WRC. The basic procedure is for existing Group N car which are authorised for use in Class 3. When the upgraded kit is added it becomes an R4 and is authorised to run in Class 2. There are specific areas allowed in this upgrade: longer travel suspension with revised geometry, lighter weight generally, stiffer chassis and improved under-bonnet cooling. Engines have to be unchanged and 33mm restrictors fitted. Cars can be upgraded privately by competitors using officially supplied components or by authorised preparation companies. Both Mitsubishi and Subaru have homologated the changes which can be used on two models – the Evo IX and Evo X, and the familiar five- door (hatchback) Subaru GRB and the newer four-door GVB models. Modifications can be carried out piecemeal but must always feature side door protection foam inserts. In the case of Mitsubishi, the upgrade work was aimed at providing budget- friendly conversion work and homologation was granted as of April after development work as a joint venture between Ralliart Italia and MML Sports in Britain. There were initial difficulties with the FIA because of a conflict of rules as to whether the R4 cars could run in WRC events with other than Michelin control tyres, and eventually the teams were told they could not. The first appearance of a Mitsubishi Evo X R4 was in Sardinia with Matti Rantanen. The total weight saving for both the Evo IX and Evo X models is reckoned to be about 60kg. The extended top mounts of both the front and rear suspension allow improved castor angles rather than increasing wheel travel. In the case of Subaru the two new bonnet orifices have had a marked effect on the engine performance. It is claimed that under bonnet temperatures themselves have been reduced by 30-40 degrees. Considerable work has been done with the suspension including a completely new subframe, roll cage stiffening, extended wheel travel and strengthening of the suspension with wider use of spherical bearings. It is claimed that the car is nicer, stronger and quicker to drive and up to 75- 80kg lighter! The debut of the car was the IRC event in Corsica with Toshi Arai while PG Andersson makes the debut of the car in the WRC in NORF this year. Development of Group R4 cars is continuing apace, and the benefits – and the corresponding performance equivalence with Class 2 Super 2000 cars – are still hard to define, and in any case are still highly dependent on the rally conditions, but certainly R4 cars are generally about between 0.6 and 1.0 second/kilometre faster than their basic N4 versions and still seem to be slower than the Class 2 S2000s. At this time R4 is going fine, but R- GT (Class 4, for sports cars) has not progressed. Here come the R4 cars ...