This post discusses the differences between 3-pin TGVs and 5-pin TGVs.
What is a TGV?
A TGV or Tumble Valve Generator is a piece of emissions equipment that reduces the air into the engine when only a small amount of air is required. It's located in between the heads and the upper intake manifold (upper plenum). A butterfly (or flapper) opens and closes depending on the engine's air needs. When the butterfly is closed, a small bypass allows air to pass through to keep the engine running. When the butterfly opens, it allows maximum airflow through the intake and into the heads.
Just a quick note. When replacing TGV sensors, you must clock them when they are installed. Click this link for a good how-to.
What does the TGV sensor do?
The sensor on each butterfly is there so the ECU can monitor the current position of the valve and decide whether it needs to be opened or closed. It can also use this signal to detect a failure if it tries to open or close and doesn't see the appropriate voltage.
What does the TGV motor do?
Based on the sensor information, the ECU will signal the TGV motor to open or close.
What are the differences between 3-pin and 5-pin TGVs?
While both models technically have 5 wires for the TGVs, the older models split the sensor (3-wires) and motor (2-wires) to the front and back of the TGV. You'll notice that the TGV on one side has the position of the motor in the front and the sensor in the back, while the other side has the sensor in the front and the motor in the back.
The 5-pin TGVs combine the motor and the sensor into a single part. You'll also notice for these models that this part is located on the front of one side and the back on the other side of the engine.
The Problem with Converting between 3-pin and 5-pin TGVs
The most common reason to switch between the two models is that the 3-pin versions have a side feed injector variant which is usually less desirable because the injector options are more limited than the top feed injectors. The problem with switching between 3-pin and 5-pin is the polarity of the motors and the sensors. The voltage to open/close the motor and the ECU's understanding of the position of the valves reverse between the 3-pin and 5-pin models. We've tried a few different ways to solve this but have yet to find a solution that properly opens and closes the valves and does not produce a check engine light.
Side feed injector to top feed injector solution for 3-pin TGV models.
You're in luck! The 2002-2005 WRX used a top feed injector and a 3-pin TGV setup. This would be your best bet for a top feed conversion.
Turbo models with 3-pin TGVs
2004-2008 Forester XT
2004-2006 Baja XT
2005-2006 Legacy GT
2005-2006 Outback XT
Turbo models with 5-pin TGVs
2009-2018 Forester XT
2007-2009 Outback XT
2007-2012 Legacy GT
If you need replacement connectors for the TGVS, we carry them below.