Oxygen Sensor Bung Plug
What Is an Oxygen Sensor Bung Plug?
An oxygen sensor bung is a threaded fitting or weldable component that provides a location to install an oxygen sensor in the exhaust system. The bung plug is its companion piece — a threaded cap that seals the bung opening when an O2 sensor is not installed in that port. Together, they are fundamental building blocks of any custom or modified exhaust system.
Located in the exhaust system, the oxygen (O2) sensor measures the amount of oxygen in the exhaust gases and compares it to the oxygen content in the air, sending that information to the Engine Control Unit (ECU) to adjust the air-fuel mixture. O2 sensors help the ECU maintain the correct air-fuel ratio by signaling when the engine is running rich or lean, allowing for more efficient combustion, improved fuel economy, and lower emissions. When an exhaust bung exists but no sensor is being used in that location — such as during a catback swap, turbo build, or custom header fabrication — a bung plug seals the opening and prevents dangerous exhaust leaks.
Why Bung Plugs Matter in Custom Exhaust Builds
Oxygen sensor bungs and plugs are commonly used in exhaust fabrication to accommodate wideband and narrowband O2 sensors for tuning, monitoring, and engine management. A weld-in bung allows an O2 sensor to be screwed into your exhaust system and is also useful for air/fuel ratio measurements when dyno testing. When a bung port is present but unused, a plug is used for sealing off O2 bungs when not using an O2 sensor or wideband port.
Selecting the right plug is just as important as the bung itself. Selecting the correct oxygen sensor bung is important to ensure proper installation and functionality. Start by considering the thread size, ensuring it matches the specifications of your oxygen sensor — common thread sizes include 18mm, 12mm, and 14mm. Consider the material of the bung, ensuring it is compatible with your exhaust system and can withstand high temperatures and corrosive environments. Stainless steel and zinc-plated mild steel are the most common materials, each offering reliable sealing and resistance to the extreme heat cycles of performance exhaust applications.
Tips for Installation
- Locate the sensor or bung 90° to the exhaust gas stream, and position it with a minimum 10° upward angle to prevent liquid buildup in the sensor element.
- When installing an O2 sensor or plug, use an O2 sensor–compatible high-temperature–resistant grease on the threads.
- Do not have the bung plug or an oxygen sensor installed when welding the bung in place, as welding can distort the bung — it is recommended to chase or tap the threads after welding.
Top Brands for Oxygen Sensor Bung Plugs
Vibrant Performance is the go-to name for exhaust fabrication hardware, and their O2 sensor bung plug lineup is a prime example of why. Vibrant Performance oxygen sensor fittings and bung plugs are engineered to give fabricators, tuners, and performance enthusiasts the precision and durability they need when installing or relocating oxygen sensors — whether building a custom exhaust, adding wideband monitoring, or upgrading a turbo system. Vibrant Performance hex head oxygen sensor bung plugs are made of zinc-plated mild steel to ensure lack of thread damage during hot and cold heat cycles during installation.