This EGT thermocouple measures exhaust gas temperature for engine tuning and monitoring. It is a Type K (Chromel/Alumel) sensor — the industry-standard thermocouple type for motorsport EGT — with a 3/16-inch (4.76 mm) probe and an exposed sensing junction for fast response (250 ms time constant). The leads are open-ended (unterminated), so you cut and terminate them to suit your amplifier, dash or ECU EGT input. Exhaust gas temperature is one of the most direct indicators of mixture and per-cylinder load, which is why a fast-responding EGT probe is a core tuning sensor on gasoline, alcohol, natural-gas and nitrous engines.
Technical Specifications
| Property | Value |
|---|---|
| Sensor type | Type K thermocouple (Chromel / Alumel) |
| Probe diameter | 3/16 in (4.76 mm) |
| Junction | Exposed (fast response) |
| Response time constant | 250 ms |
| Leads | Open-ended (unterminated) |
| Sheath material | Inconel or stainless steel |
| Usable EGT range | up to ~900–1000 °C continuous (Type K rated to 1260 °C) |
| Recommended fuels | Gasoline, alcohols, natural gas, nitrous |
| Mounting | 1/8 in NPT weld bung + compression fitting |
Wiring and polarity
The bare leads have no factory colour. Identify the negative leg with a small magnet — Alumel (−) is magnetic, Chromel (+) is not. Polarity matters: reversing the leads inverts the reading.
| Leg | Alloy | Polarity | Magnetic? | ANSI colour | IEC 60584 colour |
|---|---|---|---|---|---|
| Positive | Chromel (Ni-Cr) | + | No | Yellow | Green |
| Negative | Alumel (Ni-Al) | − | Yes | Red | White |
Extend only with Type K (KX) thermocouple wire — copper extension creates a second junction and introduces error. Terminate to a Type K input or a K-type amplifier with cold-junction compensation.
Type K calibration (cold junction 0 °C)
| Temperature | Output (mV) |
|---|---|
| 0 °C | 0.000 |
| 250 °C | 10.153 |
| 500 °C | 20.644 |
| 750 °C | 31.213 |
| 900 °C | 37.326 |
| 1000 °C | 41.276 |
Type K output is non-linear, so the conditioning amplifier or ECU input must apply cold-junction compensation and linearisation. Reference values per NIST ITS-90 / IEC 60584-1.
What you need to read it
- Miniature K Type Thermocouple EGT Connector, In-line Male — terminate the bare leads to a standard miniature K plug
- Emtron ETC4 CAN EGT Controller for 4 Sensors — Type K amplifier with cold-junction compensation and CAN output
- EGT Sensor K Type 3 mm Inconel Tip — 3 mm grounded-tip alternative when durability matters more than response speed
What thermocouple type is this?
Type K (Chromel/Alumel), the standard type for motorsport EGT. Type K is rated to 1260 °C; in exhaust use it is good for roughly 900–1000 °C continuous.
How do I tell the positive lead from the negative?
The negative leg (Alumel) is magnetic and the positive (Chromel) is not — check with a small magnet. Polarity matters; swapping the leads inverts the reading.
What amplifier or input do I need?
A Type K input or a K-type amplifier with cold-junction compensation, such as the Emtron ETC4 CAN EGT controller, or the EGT input on an AiM, MoTeC or Ecumaster dash or ECU.
Can I use ordinary wire to extend the leads?
No. Extend only with Type K (KX) thermocouple wire (yellow ANSI / green IEC). Copper wire creates a second junction and introduces measurement error.
How durable is the exposed junction?
The exposed junction gives the fastest response (250 ms) but is the most fragile of the junction types. For a more rugged probe, the grounded-tip 3 mm Inconel EGT sensor trades a little response speed for durability.
Where should I mount the probe?
In a 1/8-inch NPT weld bung in the primary header, about 25–50 mm from the head and before the first bend, with the tip in the centre of the gas stream.
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