Guide · RaceCapture

EGT on RaceCapture

RaceCapture/Pro logs an exhaust gas temperature amplifier like any 0 – 5 V sensor: one analog channel with linear scaling. This guide covers which units can take one, the wiring, the channel setup in the RaceCapture app, and a dashboard alert.

Checked against the Autosport Labs wiki, September 2026.

00What you need

• A RaceCapture/Pro MK4, MK3 or MK2, or a RaceCapture/Apex. Those have 0 – 5 V analog inputs. RaceCapture/Track has none of its own, and this guide doesn't cover adding them with an AnalogX2 CAN module.
• The RaceCapture app, connected to the unit.
• An EG5 for the unit's 5 V reference, or an EG12 for switched 12 V.
• A Type K probe and a bung or O2-port adapter for it, bought to the specifications under Recommended to use with.
• A multimeter.

Electrical

01Pick an input

RaceCapture/Pro MK4 and MK3 and RaceCapture/Apex have eight 0 – 5 V analog inputs, and MK2 has seven. They read 12-bit, with no pull-up resistors, so there's nothing to switch off.

• MK4: analog inputs 1 – 8 are on pins 4, 5, 7, 8, 1, 2, 9 and 3 of the M12 analog connector. The analog harness also fits the digital port, so check which one it's in.

02Wire it

• MK3 and Apex harness: red is the unit's 12 V power, not 5 V. An EG5's red goes to the yellow wire.
• MK4 single-channel pigtail: brown is ground, blue is 5 V, and black is the signal, not ground.
• EG12: take a fused switched 12 V feed from the car, and ground the module at the same point as RaceCapture.
• Ground at RaceCapture. Autosport Labs says to ground sensors at the same point as the unit. Every 4 – 5 mV of ground offset reads as about 1 °C.
• An EG5 goes on a 5 V sensor supply only, never 12 V. It has no reverse-polarity protection either, so check red and black before you power up.
• Neither output can go much above 5 V. The EG5 can't rise above its own 5 V supply, and the EG12 is capped at about 5.3 V.

Probe side

• The thermocouple cable is cut square. Take the jacket back, strip the yellow and red, and splice yellow to the probe's + and red to −. The cable is Type K extension, so the splice can sit anywhere along its run.
• Check the polarity. A reversed probe reads right at room temperature, so once it is spliced, warm the probe's tip: the reading must rise. If it falls, swap the probe's two leads at the splices. On a probe whose leads are not marked, the − lead is the one a magnet sticks to.
• Need more reach? Extend from the probe end with Type K extension wire, never copper.
• Ungrounded probes only. An ohmmeter from either lead to the sheath should read open.
• Mount the module somewhere cool, on the cabin side of the firewall or an inner fender: under 50 °C for an EG5, under 100 °C for an EG12.

Software

03Set it up in the RaceCapture app

1. Open Setup → Analog Sensors and choose the input you wired.
2. Under Channel, set the channel name, such as EGT.
3. Set Sample Rate. Temperature changes slowly; the Autosport Labs calibration guide suggests 1 – 5 Hz.
4. Set Mode to Linear. The formula is Raw × multiplier + offset, with Raw in volts:
   EG5: 200 and 0 for °C, or 360 and 32 for °F.
   EG12: 250 and 0 for °C, or 450 and 32 for °F.
5. Press Write. Nothing takes effect until you do, and the button pulses while there are unsent changes. Save keeps a backup file.

Mapped mode works too: enter the two calibration points above and repeat the last point across the remaining columns. Linear keeps scaling past the last point; Mapped holds the end value.

A dash means past that model's range.

04See it and log it

• Unlock the dashboard with its gear icon, choose Add gauge, and pick your channel in the gauge's settings.
• RaceCapture/Pro and Apex log to an SD card, FAT32 and 32 GB or smaller. Setup → Automatic Control sets the logging start and stop triggers. Speed is the usual trigger channel.
• The app records sessions too, for review in Analysis. SD card logs are plain CSV.

05Optional: a high-EGT alert

Dashboard alerts can pop up a warning or change a gauge's colour when EGT crosses a limit.

1. Open the dashboard gear, then More Settings → Alerts, and pick your EGT channel.
2. Add a rule: set its active range from your limit upward, and its active-after time for how long it must hold.
3. Add new Action: a popup alert, or Set Gauge Color.

Those alerts live in the app. For a light that doesn't depend on the app, a Lua script can drive a ShiftX3 or, on RaceCapture/Pro and Apex, a GPIO output.

Troubleshooting

It reads a steady, believable temperature with nothing connected

An unconnected RaceCapture input floats anywhere from 0 to 5 V, so check the yellow wire. To test the input itself, unplug the yellow wire, set Mode to Raw and press Write. With the unit on 12 V power, jumper the input to ground (about 0 V), then to Vref (about 5 V). Then set Mode back to Linear and press Write.

It tops out below full scale on USB power

On USB power alone, Vref sits near 4.7 V and inputs read no higher than about 4.6 – 4.8 V. Test on 12 V power.

The channel setup vanished after an update

Firmware updates can reset the configuration. Save it to a file before updating.

It reads near full scale on a cold engine

The probe is disconnected or open. Both modules drive their output high when the probe circuit is open, so an open probe reads hot, not cold.

The reading falls as the exhaust heats up

The probe's leads are reversed at the splices. A reversed probe reads right at room temperature, then falls toward 0 °C as its tip heats. Swap the probe's two leads.

The reading jumps with revs, fans or the alternator

You have a grounded probe, or the black wire goes to the chassis instead of RaceCapture's ground. Fit an ungrounded probe and move the black wire to a RaceCapture ground.

It reads high once the engine bay heats up

The module is mounted somewhere too hot, or there's copper wire between the probe and the module.