Under this section I will share work done on the Toyota Celica GT-FOUR ST185.
The first 21 units ST185 were built in December 1988 as prototypes for various tests. The production model was launched in Japan in September 1989, and delivery began a month later.
The 3S-GTE in the GT-Four features an air-to-air intercooler and CT26 twin entry turbo to eliminate exhaust gas interference. The Japanese market GT-Four has 225 PS (165 kW; 222 hp) of power and 304 N·m (224 lb·ft) of torque, a result of more aggressive ignition advance and ceramic turbine. The Full-time 4WD system in the GT-Four has viscous coupling limited slip center differential and some models are equipped with a Torsen rear differential.
All export market GT-Four are wide-body Liftback models with flared fenders. The Japanese market GT-Four was also offered as normal/narrow body from 1989 to 1991.
In August 1990, the wide body GT-Four A was added into the Japanese lineup. Super Live Sound System with 10 speakers became standard on the GT-Four A.
There are three different gearboxes for ST185 GT-Four. The E150F with 4.285 final gear ratio was installed in the Japanese market and All-Trac. European and Australian specs come with E151F with 3.933 ratio. The Japanese market only GT-Four Rally has E152F with close ratio on the 1st through 4th gear and 4.285 final ratio. All the RC/Carlos Sainz/Group A Rallye have E151F.
Anti-lock braking system (ABS), Leather interior, Sunroof, and System 10 Premium Sound System are optional on '90–'92 All-Trac Turbo, and standard on '93 model year All-Trac Turbo. With its sport-style interior, power-operated driver's seat, auto tilt-away steering wheel, SRS Airbag, and cruise control as standard equipment, the ST185 All-Trac Turbo was the most expensive Celica yet. With a 2.0 L turbocharged 3S-GTE producing 149 kW (203 PS; 200 hp) and 200 lb·ft (270 N·m) of torque, it was the most powerful Celica ever sold in the USA.
The European versions have standard ABS. Sunroof came standard in the UK models, or optional for cars in the Continent. However, System 10 Premium Sound System and Leather interior were only available as options in selected European countries, and were not offered in the UK.
The Australian spec is less luxurious than other destination models. Cruise control, leather, and sunroof were not offered. Early models don't have ABS and fog lights which became standard few months after introduction. However, Australia was the country with the large numbers of ST185.
Like other Celicas, the GT-Four received minor changes in August 1991 for the 1992 model year. This facelift included the new Toyota ellipse emblems on the hood and trunk, restyled tail lights with smoked red frame, and shorter gear shift. The Japanese models also got round-shape front fog lights. The All-Trac Turbo retained the automatic air conditioner, but the fan switch was changed from the push button type to the more conventional rotary type, the same one as in the lesser grades Celica.
The special rally edition of 5000 units was known as the GT-Four RC was launched in September 1991 in Japan. The export version is known as Carlos Sainz(CS) Limited Edition in Europe (in honour of their famous WRC driver), or Group A Rallye in Australia.