Production Spark Plug Modified to Accept
Optrand Miniature Cylinder Pressure Sensor

The PSIplug is a user-selected, modified production spark plug that accepts Optrand miniature M3.5 or M4.5 sensor. A detachable sensor is mounted in a spark plug collar and senses combustion pressure through a passage linking the sensor diaphragm to the cylinder chamber. Since no modifications to the electrodes are required, the modified spark plug retains the original electrical and thermal characteristics. The PSIplug/Sensor assemblies are particularly useful for engine knock studies.

Modified Spark Plug Collar Diameter:

Accepted Sensor Sizes:

Sensor Pressure Ranges:

Min. 22mm with M3.5 sensor,
        25mm with M4.5 sensor

M3.5x0.6 or M4.5x0.5

M3.5 sensor: 0-100 bar (~1,500 psi)
M4.5 sensor: 0-70 bar (~1,000 psi) or 0-200 bar (~3,000 psi)

PSIplug combines the miniature 2.8mm or 3.8mm diaphragm sensor with a modified production spark plug. The assembly offers uncompromising spark plug performance and pressure reading accuracy of a head-mounted sensor.