Where Should a CHT Sensor Be Mounted—Under the Spark Plug or in a Separate Bo

Both mounting methods are used in motorsports and performance applications, and each has its own advantages depending on your engine design, accuracy requirements, and installation constraints.

Mounting Under the Spark Plug (Ring-Type CHT Sensor):

This is the most common and convenient method of installing a CHT sensor, especially for air-cooled engines or racing engines with limited access to the cylinder head.

Pros:

  • Quick Installation – No modification to the engine is required.
     
  • Non-Invasive – Installs simply by removing the spark plug, sliding the sensor ring over the threads, and reinstalling the plug.
     
  • Good Relative Accuracy – Provides real-time temperature data closely correlated to cylinder head temperature trends.
     

Cons:

  • Less Direct Measurement – Since the sensor is clamped under the spark plug, the reading may be slightly lower than the actual metal temperature of the combustion chamber area.
     
  • Sensor Movement Risk – Repeated removal of the spark plug may slightly shift the sensor and affect consistency.

Mounting in a Dedicated Bore (Threaded CHT Sensor):

This method involves drilling and tapping a hole in the cylinder head for direct sensor insertion. It is often used in professional racing, dyno testing, or advanced tuning applications.

Pros:

  • More Accurate Measurement – The sensor is in direct contact with the head material, providing highly accurate and repeatable readings.
     
  • Permanent Installation – No interference with spark plug maintenance or torque values.

Cons:

  • Requires Engine Modification – Drilling and tapping must be performed precisely to avoid damaging the cylinder head or affecting structural integrity.
     
  • More Time-Intensive – Installation and setup are more complex compared to ring-style sensors.

Which Option Is Right for You?

Factor

Ring Under Spark Plug

Dedicated Bore

Ease of Installation

✅ Easiest

❌ Requires machining

Accuracy

✅ Moderate

✅✅ High

Spark Plug Interference

❌ Yes

✅ No

Long-Term Durability

✅ Good

✅✅ Excellent

Professional Use

✅ Common

✅✅ Preferred

Summary:

  • Use a ring-style CHT sensor under the spark plug for quick, non-invasive installation, especially in air-cooled engines or when modifying the head isn’t practical.
     
  • Use a dedicated bore-mounted sensor when maximum accuracy and long-term reliability are critical—such as in race engines, dyno testing, or advanced data logging.

Need help choosing the right CHT sensor for your application?
👉 Contact us for expert advice.

 

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CHT Sensors