What is a TGV on a Subaru?

If you own a Subaru, you may have heard of the Tumble Generator Valve, or TGV for short. But what exactly is it, and why does it matter? In this article, we’ll dive into the details of this important component, explaining its purpose and impact on your vehicle’s performance.

Key Takeaways

  • The Tumble Generator Valve, or TGV, is a component found on some Subaru engines.
  • Its purpose is to improve the air/fuel mixture in the engine’s cylinders, resulting in better combustion and improved performance.
  • TGVs are known to suffer from issues with carbon buildup, which can lead to a variety of problems including rough idling and reduced power.

Now, let’s take a closer look at the TGV and its role in your Subaru’s performance.

What is a TGV?

The Tumble Generator Valve is a component found on some Subaru engines, specifically those with the company’s "Boxer" design. The Boxer engine features horizontally opposed pistons, with two cylinders on each side of the engine block. This design allows for a lower center of gravity and improved handling, among other benefits.

The TGV is located on the intake manifold of the engine and is responsible for controlling the flow of air into the engine’s cylinders. Its purpose is to improve the air/fuel mixture in the cylinders, resulting in better combustion and improved performance.

How does a TGV work?

The Tumble Generator Valve works by introducing a swirling motion to the air as it enters the cylinders. This swirling motion, or "tumble," helps to mix the air and fuel more thoroughly, ensuring that each cylinder receives a consistent mixture.

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When the TGV is closed, air flows into the engine in a relatively straight line. But when it opens, a flap inside the valve redirects the air, causing it to swirl around as it enters the cylinder. This improves the mixing process and allows for more complete combustion.

Why does the TGV matter?

The Tumble Generator Valve plays an important role in your Subaru’s performance. By improving the air/fuel mixture in the cylinders, it can lead to better combustion and more power. This can result in improved acceleration, better fuel efficiency, and smoother operation overall.

However, TGVs are also known to suffer from issues with carbon buildup. Over time, carbon can accumulate on the valve and in the intake manifold, leading to a variety of problems. These can include rough idling, reduced power, and even engine misfires in severe cases.

How to diagnose TGV issues

If you’re experiencing problems with your Subaru’s performance, it’s possible that the Tumble Generator Valve is to blame. Here are some signs that you may have an issue with your TGV:

  • Rough idling: If your engine is running rough at idle, it could be a sign of carbon buildup in the TGV or intake manifold.
  • Reduced power: If you’re experiencing a noticeable decrease in power or acceleration, it could be due to a clogged TGV.
  • Check engine light: A malfunctioning TGV can trigger the check engine light on your dashboard.
  • Engine misfires: In severe cases, a clogged TGV can cause the engine to misfire, which can be felt as a loss of power or a rough running engine.
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If you’re experiencing any of these symptoms, it’s important to have your TGV inspected by a qualified mechanic. They can diagnose the problem and recommend the appropriate repairs.

How to fix TGV issues

If the problem with your Tumble Generator Valve is due to carbon buildup, there are several steps you can take to address the issue. Here are some common solutions:

  • Cleaning: One of the most effective ways to remove carbon buildup from the TGV and intake manifold is to clean them. This can be done with specialized cleaners and tools designed for this purpose.
  • Replacement: In some cases, the TGV may be too damaged to be cleaned effectively. In this case, it may need to be replaced with a new unit.

It’s worth noting that some Subaru owners choose to "delete" their TGVs altogether. This involves removing the valve and replacing it with a straight pipe or block-off plate. While this can improve airflow and potentially increase power, it’s not a recommended modification for everyone. It can also lead to issues with emissions compliance and can potentially harm your engine if not done properly.

Conclusion

The Tumble Generator Valve is an important component of some Subaru engines, playing a crucial role in improving the air/fuel mixture and overall performance of the vehicle. However, it’s also prone to issues with carbon buildup, which can cause a variety of problems. If you’re experiencing issues with your Subaru’s performance, it’s important to have your TGV inspected by a qualified mechanic. With proper maintenance and care, your TGV can help keep your Subaru running smoothly for years to come.

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FAQ

Q: What Subaru engines have TGVs?

A: TGVs are typically found on Subaru engines with the company’s "Boxer" design, including the EJ20, EJ25, and FA20.

Q: Can you remove the TGV from a Subaru?

A: Yes, it’s possible to remove the TGV and replace it with a straight pipe or block-off plate. However, this is not recommended for everyone and can lead to issues with emissions compliance and engine damage if not done properly.

Q: What causes carbon buildup on TGVs?

A: Carbon buildup on TGVs is caused by a combination of oil vapor, fuel, and other contaminants that accumulate over time. This buildup can cause a variety of problems with the valve and the engine overall.

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Alton Brobst

As a longtime Subaru enthusiast, Alton brings a wealth of knowledge and experience to our blog. From his early days of tinkering with engines to his current role as a certified Subaru technician, Alton has seen it all when it comes to Subarus. When he's not working on cars, he enjoys hiking and exploring the great outdoors.

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