Nowadays it’s all too simple for the likes of the FIA to accurately control the performance of a turbocharged car through the careful implementation of restrictors of different sizes. It’s a method that’s in use across the board, from the BTCC to the World Rally Championship and beyond, but it hasn’t always been this way. Indeed, for much of the late ‘80s it was decidedly tricky for the powers that be to govern the amount of boost being generated by a given car, with the WRC being among the toughest of a tough bunch to manage.

It didn’t take long before late ‘80s Group A cars like the Delta Integrale were making an easy 400bhp and probably more, and with the horrors of 1986 fresh in their mind, the FIA opted to pursue a programme of mandating the fitment of increasingly restrictive turbo restrictors. 

The Celica ST205 was a new and largely unproven car come the beginning of the 1995 season

Things reached a nadir in the lead up to the 1995 season, when the FIA once again increased the size of the restrictor for all Group A cars competing at the top of the sport. The new, 34mm restrictor adversely impacted all of the teams, though not equally; Mitsubishi’s ‘long stroke’ 4G63 could call upon greater torque than rival offerings from Subaru, Ford, and the subject of Turbo Tuesday today, Toyota Team Europe.

That same season saw TTE grappling with a new car, the latest variant of the hitherto dominant Celica GT-4, the ST205. The new machine had made its competitive debut in the final rounds of the 1994 season and while reliable and quick enough to set decent stage times, it was far from universally loved by the men tasked with driving it, Didier Auriol, Juha Kankkunen and Armin Schwarz. 

The 1995 World Rally Championship kicks-off in customary fashion, the Monte Carlo Rally

The need to grapple with the new car, coupled with the decrease in peak power enforced upon the team through the restrictor change, probably conspired TTE to commit one of the best known and most ingenious motorsport cheats ever devised. 

Not that there was any hint that Toyota was playing anything other than fair for most of the season. The Celica was forced to play second fiddle to the Impreza 555s of Colin McRae and Carlos Sainz, and also the Evo III of Tommi Makinen, with Auriol winning just the once, at home on the French island of Corsica.

The sole win of the season for Auriol (and the ST205’s only WRC event victory) occurred on the Tour de Corse

All of this meant that TTE’s engineering ruse could well have remained undetected and probably would have done, were it not for a series of (for Toyota at least) unfortunate events. The first occurred at Rally Australia and the Langley Park super special stage, where a pair of cars were effectively ‘raced’ against one another. This unusual layout provided the FIA with the opportunity to benchmark the various Group A cars against one another, and it was noted that the Celica was noticeably faster away from the line than the Evo, the Impreza or the Escort. 

The final staw took place some weeks later on the tarmac of Spain, a surface all but detested by Toyota’s Juha Kankkunen. It was therefore something of a surprise to find the Finn leading and leading comfortably, or at least he was until he went off the road and crashed heavily. 

Kankkunen’s battered Celica rolls out of contention…and into the scrutiny of the FIA!

It was enough to prompt the FIA to seize turbochargers from all four teams for a careful, nut-and-bolt disassembly. It was found that the turbo restrictors were modified in a number of fiendishly clever ways and the scale and complexity of Toyota’s nefarious behaviour became apparent. 

The restrictor was designed to be able to move freely and could therefore be positioned further away from the turbine, significantly further than the 50mm limit speficied by the FIA. The ingeniously clever setup also enabled air to enter the engine without having first passed through the restrictor, a further contravention of the rules governing the sport. This bypass valve was actuated by a spring and worked in conjunction with a highly modified tube leading from the FIA mandated restrictor to the turbo. This could open the bypass valve by a full 5mm, hence the Celica’s performance advantage and supposed power advantage of up to 50bhp. 

TTE’s very public shaming was tempered by a general acceptance that while the device had been against the rules and indeed the spirit of the WRC, it had been beautifully engineered and executed bit of cheating. 

Max Moseley begins to publicly disassemble the Celica’s turbo assembly

Max Mosely was especially vociferous in his description of the device: 

“Inside it was beautifully made. The springs inside the hose had been polished and machined so not to impede the air which passed through. To force the springs open without the special tool would require substantial force. It is the most sophisticated and ingenious device either I or the FIA’s technical experts have seen for a long-time. It was so well made that there was no gap apparent to suggest there was any means of opening it.”

The results of Toyota’s public shaming were spectacular. The team was stripped of all its points accrued in 1995 and was banned from WRC competition outright for the following season. It was also enough to convince Toyota to abandon the Celica, the basis of its rally cars since the early ’70s. Its first World Rally Car would be based upon the Corolla.

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