Tuesday, February 24, 2015

Homologation Special

Words & Snaps by Ben

Born back when the WRC required to have "Homologation Specials", the Celica GT-Four is among the rare cars that were brought to the roads as detuned competition vehicles

When Yoshi encountered this ST185, the second generation of the Celica GT-Four and second-last model Toyota ever pit in the WRC, he knew he found a unicorn. A unicorn with pop-up headlights. Who would say no to that?

In 1974, the FIA set up a new rule for manufacturers to enlist their creations in the WRC: the Homologation Specials. To avoid having too outlandish, purpose-built vehicles that no one could relate to lining up on the grid, manufacturers had to make production runs of their rally cars. Group A had to have a run of at least 2,500 units and Group B of 200 units.

To qualify, the production cars had to be very similar to their race counterparts, with identical mechanical and electronic parts, and even body designs.

These rules redefined the way car manufacturers built their racing monsters: instead of taking a production car and beefing it up, they switched the recipe around and built race cars first, before devising its down-tuned road-going version.

The FIA rule book gave birth to rather interesting Homologation Specials, which were built with little care of the road-worthiness of the production model, as long as it gave them more freedom with the rally version. For example, the rules stated that the racing version's wheels could not exceed the size of the homologated version. This translated in the public getting cars with the biggest wheels the manufacturers could fit on them, so that they would have wider wheel arches, and thus more freedom to fit whatever setup they wanted in the WRC line-up vehicle.

Needless to say, Homologation Specials were an awesome breed of cars. They were literally road approved race cars in disguise.

Introduced back in 1988, the Celica GT-Four marked a new turn in the World Rally Championship: it was the first time the Japanese lined up an AWD turbocharged platform on the starting grid.

As it clinched Driver's and Manufacturer's Championships, the other Japanese manufacturers replicated the AWD turbocharged recipe, with the Galand VR-4, Lancer Evo, Legacy and Impreza to create the legends we all know today.

While the ST185 became Toyota's most successful rally car, and its third version, the ST205 continued to set trends by being the first car in Group A to sport an Anti-Lag System, which was subsequently quickly adopted by the other teams.

After getting some hands-on experience at the wheels of a varied list of cars, including an Alfa Romeo GT 1.8, a Saab 9-3 Troll Edition, a Lancer EX-GT, and a Lancer CS5 1.8 GDI turbo, Yoshi couldn't simply leave his Celica unmolested, and he thus began to bring in his own additions to Toyota's rally-bred all-wheel drive creation.

While he had plans to upgrade the Celica mechanically, Yoshi loved the smooth, curvy design of the ST185, and thus decided to leave her looks as they came from the factory, less the logo and model name, which he never put back after getting the car resprayed.

Yoshi complemented the fresh blue hue of the body with a set of 17" Rota Boost, shod in Sumimoto's HTR Z III sizing 215/50. To preserve the rally history of his car, as well as to keep her easy to drive on a daily basis, Yoshi made sure that the Tein Superstreet Coilovers retained a reasonable height.

Handling is one of the key aspects of a rally car, but as much as the Homologation Specials had to be close to their road-going sisters, some elements, such as the roll cage, were not made public-friendly. With the aim of strengthening the aging chassis, Yoshi complemented the factory 3-point strut bar with a Cuzco 4-points lower brace.

Handling was further sharpened with a Whiteline antiroll bat and Super Pro bushings for the front & rear lower arms, as well as for the trailing arms.

With the handling meeting his needs, Yoshi then turned his attention to the heart of his ST185.

From the inside out, the engine has received Brian Crower conrods, topped with Wiseco pistons. The rotating assembly dances at the rhythm set by HKS high cams and adjustable cam pulleys.

Sufficient fueling is ensured by a Sard fuel rail with upgraded injectors, while a Link G4 Storm standalone ECU ensures the engine runs at its optimal rate.

Fresh air is fed into the engine through a Choon's Motorworks custom heat-shielded air intake, and expelled through a chunky HKS Silent Hi-Power catback exhaust. The fat muffler not only gives the uneven, high cam idle a nice raspy growl, it also complements the rally-heritage of the ST185 perfectly!

The ever-important engine cooling is handled by a dual-core aluminium radiator with 3 radiator fans, slotted behind the front-mounted intercooler.

Yoshi upgraded the turbo to a Garrett GTX3076 with an HKS blow-off valve, but quickly realised that while this made his ST185 fun for the drag and track, the turbo-lag made her very unpractical on a daily basis, to the point where he started preferring taking his father's car for his errands.

The Homologation Special rules stated that the WRC car had to have the same turbo as the road-going version, and Yoshi experienced first-hand why Toyota chose the CT20B as the preferred snail for the ST185. Following the expertise of Toyota's engineers, he dumped the aftermarket turbo and put the original piece back in its place.

To handle the 250WHP his setup puts down, as well as the abuse he puts his drivetrain when doing stunt driving, Yoshi mated the engine with an Excedy 3-puck clutch.

Inside, Yoshi replaced the stock front seats with a black and yellow leather set inherited from a friend.

He swapped the original steering in favour of a Momo wheel mounted on a KYB boss kit, behind which peeks out an HKS EVC to control and keep his boost pressure in check.

Above the dashboard, Yoshi fitted a Defi VSD X, for a heads-up reading of his speed. To keep tabs on his engine vitals, he added 5 Defi gauges at the top of his windscreen, reading the boost, oil temp and pressure, water temp, and exhaust temp

Yoshi's pretty happy with the way his ST185 is now, somewhere between the factory version and the all-out race monster that terrorised the WRC stages back in the 90's. Then again, maybe it could do with a few more mods?

We all know the story, and it's a never ending one. One this is set in Yoshi's mind, though, is that he aims at keeping this car for as long as he can to show the next generation what Toyota was capable of doing in the good old days. To keep it even closer to the legend, he even mentions reverting the FMIC to the stock water-to-air intercooler, one of the GT-Four's highlights when it came out.


Celica GT-Four ST185
3S-GTE, 1,998cc, Turbocharged
Drive Layout
Front Engine, AWD
Max Output

Power Mods
Choon’s Motorworks Custom Air Intake With Heat Shielding
Dual Core Aluminium Radiator, 3 Radiator Fans, Front Mounted Intercooler
Sard Fuel Rail With Upgraded Injectors
Brian Crower Conrods, Wiseco Pistons, HKS Hi-Cams, HKS Adjustable Cam Pulleys
Toyota CT20B Turbocharger, Greddy BOV
HKS Silent Hi-Power Catback Exhaust
Excedy 3 Puck Clutch
Link G4 Storm Standalone ECU

Rota Boost 17x8jj
Sumitomo HTR Z III 215/50R17
Tein Superstreet Coilovers
Cusco 4-Points Lower Brace
Super Pro Bushings For Front & Rear Lower Arms, and Trailing Arms, Whiteline Sway Bar

Leathered Front Seats
Steering Wheel
Momo Steering Wheel With HKB Boss Kit
Lonza Aluminium Pedals
5 Defi Gauges (Boost, Oil Temp, Oil Pressure, Water Temp, Ext Temp), Defi VSD X, HKS EVC

Acknowledgments: Yoshi would like to give special regards to his grandma who has been very supportive of him and his passion. He would also like to thank to Sam, Ah Long, and all the friends he met during his various car ownerships.

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