IF YOU AIN’ T CHEATING, YOU AIN’ T TRYING
WRC Toyota Celica GT-Four restrictor
More air means more power, so Toyota wasn’ t going to let a restrictor hamper its Celica WRC car’ s performance
Toyota’ s turbo restrictor bypass on its Group A Celica GT-Four rally car was not just the ingenious bending of rules, it was a complete cheat. An imaginative, sophisticated and well-crafted cheat.
After the wild, terrifyingly fast and eventually dangerous era of Group B, rallying’ s governing body, the Fédération Internationale de l’ Automobile( FIA), wanted to keep speeds down. The easiest way to do that was to limit power and, as the vast majority of the field consisted of turbocharged cars, a simple solution was to restrict air to the turbos in each car. For the 1995 season, the choke for the turbo’ s inlet could be no more than 34mm in diameter. This capped power to around 300hp – quite a lot lower than the 600hp-or-so the later Group B cars had.
Knowing just how keen motorsport engineers are to purposefully misinterpret rules to gain an advantage, the World Rally Championship( WRC) scrutineers were thorough in their inspections. That meant, if you were going to mess with a restrictor, you had to be exceptionally clever. And the engineers at Toyota Team Europe( TTE) were exceptionally clever.
TTE’ s Celica was fitted with a restrictor. And any time the scrutineers took apart the turbo intake to inspect it, they found that the unit that held the restrictor in place against the turbo inlet was correct and legal. Because when it wasn’ t on the car, it looked exactly as the rules stated, even to the expert eye.
Toyota Team Europe’ s air restrictor bypass was one of the most ingenious cheats in motorsport history
The mere act of installing it, however, changed how air flowed through it. The unit consisted of the conical restrictor held inside a rubber and steel housing. As the jubilee clips that held the restrictor unit to the turbo were tightened, they squeezed a set of springs shaped like bezelled washers that pushed the internal restrictor 5mm away from the turbo.
This movement opened up an extra channel within the unit but around the restrictor. Fresh air continued to pass through the restrictor, as was legal, while extra air was sucked into the turbo from around the outside. Some sources say an additional 25 % more air entered the turbo, good for an extra 50hp.
When it was removed for inspection again, the jubilee clamps released their pressure and the restrictor shifted back to its legal position.
The hooky restrictor unit was discovered at Rally Catalunya in 1995; some say it was so elegant and subtle that a whistleblower had to have alerted the authorities. The drivers and Toyota’ s top management said they knew nothing of the bypass unit. Still, Toyota was banned from the rest of the WRC season, and all rallies in 1996 too. But not without a nod of respect from the FIA. The then president of the body, Max Mosley, said,‘ It’ s the most ingenious thing I have seen in 30 years of motorsport. Inside it was beautifully made. The springs inside the hose had been polished and machined so not to impede the air which passed through. It is the most sophisticated and ingenious device either I or the FIA’ s technical experts have seen for a long time.’
58 The Engine Rebuilder Issue 04