BUDAPEST, Hungary - Defending F1 Constructors' champion team Red Bull has been forced to change its engine mapping for the 2012 Hungarian F1 GP on Sunday.Motor racing's ruling body, the International Automobile Federation, on Thursday confirmed a clarification to the technical regulations that closed a loophole in the rules.Red Bull is believed to have been running its cars - driven by defending Drivers champion Sebastian Vettel and title contender Mark Webber - with computes set to allow them to run with reduced torque in the mid-rpm range.RULES RE-WRITTENThis is perceived to have given them an illegal performance advantage that was identified on July 22 at the 2012 German GP where the stewards, when presented with an IAF report on the matter, ruled that the cars were not breaking the rules as written.The IAF has since re-written the rules and clarified the issues to ensure that the Red Bull cars will not continue to take any advantage. It issued a clarification of Article 5.5.3 within F1's technical regulations to the teams ahead of this weekend's race.It is understood that the teams will be required to supply one engine map - as a reference - that they used during the first four events of this season, which must then be approved by the governing body. Once passed by the IAF, the engine torque curves above 6000rpm must not vary by more than 2% from that reference map.Teams will be allowed to make specific requests for changes when races take place in "exceptional atmospheric conditions.Red Bull has yet to make any official reaction to the ruling but McLaren's managing director Jonathan Neale said he could not quantify the effect the clarification would have on Red Bull's performance. 'LOOKING CAREFULLY'"I really don't know," Neale said. "None of us really knows what it is that has antagonised the IAF so much as to provoke (IAF technical delegate) Jo Bauer into issuing the note he did last Sunday morning. That was quite an unusual step - I don't think the IAF would have referred to the stewards unless they had very serious concerns."It's really not for us to know or tell exactly what the Renault engine is doing in the Red Bull and therefore how much advantage they gain but I know we are not the only ones on the grid who are looking at it very carefully."The controversy over engine mapping erupted during the German GP weekend when Bauer issued a statement that said a reduced level of torque in the mid-rpm range on each Red Bull car was a breach of the regulations in itself but also because it could offer illegal aerodynamic benefits. Stay with Wheels24 for the 2012 Hungarian F1 weekend.