Turbocharger CT20b Toyota MR2 Celica 3SGTE

CT20b is one of the most popular OEM upgrades for the Toyota 3S-GTE engine. While it is technically a “small” CT26, it is widely referred to in the community as the CT20b. It was factory equipment on the Gen 3 3S-GTE found in the JDM SW20 MR2 (1994–1999) and the Celica GT-Four (ST205).

1. Performance Comparison: CT20b vs. CT26

The CT20b is superior to the Gen 2 CT26 in almost every performance metric, primarily due to its more efficient internal design.

2. Technical Specifications & Part Numbers

• OEM Part Number: 17201-74080 (Standard ST205/SW20 Gen 3).

• Manufacturer: Produced by Toyota in collaboration with Hitachi.

   

• Flange Type: Toyota “Twin Entry” 7-bolt outlet (Standard for 3S-GTE manifolds).

• Actuator: Fixed internal wastegate, typically set to 0.8–1.0 bar from the factory.

3. The “Ceramic” Risk

Most original JDM CT20b units utilize a ceramic turbine wheel.

• The Benefit: Extremely low rotational mass allows for nearly instantaneous spool and better throttle response.

• The Risk: Ceramic is brittle. Running high boost (above 18 psi) or experiencing “anti-lag” style exhaust temperatures can cause the ceramic wheel to shatter and send debris into the engine or out the exhaust.

   

• The Solution: Many performance shops offer a “Steel Wheel Conversion” during a rebuild, replacing the ceramic internals with Inconel or Steel for high-boost reliability.

4. Compatibility & Retrofitting

• Gen 2 3S-GTE (ST185 / Early SW20): This is a direct “bolt-on” upgrade. You will need to retain the CT20b’s specific oil and water lines or use a conversion kit, as the Gen 2 lines have slightly different bends.

• Gaskets: Always use a fresh 7-bolt exhaust gasket (04175-74040) to prevent leaks, as the CT20b runs higher exhaust gas temperatures than the stock CT26.