How to disconnect the T-VSV system



Please note that I am not a mechanic by trade and that I nor can be held responsible for any damage, injuries or death caused by work you perform using this website as a guideline.

T-VSV, or Turbo Vacuum Switching Valve is the name of a system which is fitted on all GT-Fours. This valve is the reason why the boost in the first two gears is lower (ST185: 50 kPa) than in the rest of the gears (ST185: 65~70 kPa). To get the same boost in all gears, you can disconnect the T-VSV. However, without fitting a boost controller, the boost will be 50 instead of 70 kPa in all gears.

Parts and tools needed

Vacuum hose with inner diameter (ID) of 6 mm (~10 cm)
Hose clamps for the above hose
2 bolts/screws/etc. to block the above hose

Basic socket set
Sharp knife

Small hands/help of a friend with small hands would be nice and makes this job easier.


Remove the intake assembly from the turbo to create space to work in:

1) Disconnect the black connector of the airflow meter (AFM)
2) Undo the hose clamp on the turbo side of the inlet hose
3) Undo the metal clamps of the airbox (4 from the top of my head) and remove the piping/AFM/airbox cover assembly

Locate the wastegate actuator - it's a drum shaped metal box in between the turbo compressor housing and engine block. There are two hoses connected to the actuator:

The one bent to the engine is the one to block. Take out the rubber hose. Cut the new hose in half so you now have two pieces of approximately 5 cm each, as pictured above. Put a bolt in each hose and make sure they can't get out easily. Put one on the engine facing actuator nipple and one on the pipe the nipple was connected to. You might need some hose clamps to make sure the system is disconnected properly. If the wastegate actuator isn't fully blocked off you risk serious engine damage.

Reinstall the intake assy and make sure you don't forget the AFM connector. Make sure all hose clamps are tightened.

Job done!

Related links

How to..
How to install an electronic boost controller
T-VSV disconnection