Racing telemetry glossary: 40 terms explained

This glossary explains the words you meet when you set up a racing HUD or read a telemetry field list. Terms are grouped by how the data travels, what the car does, and what the race adds. Which of them a game actually sends is the game’s choice.

How the data travels

Telemetry: Live data a game publishes about the car and the session: speed, RPM, pedals, forces, lap times. Dashboards, motion rigs and HUDs read it.
UDP: A network protocol that sends small packets with no handshake. Many racing games use it to send telemetry to an IP address and port, usually on your own PC. See How game telemetry works.
IP address: The address the game sends its packets to. 127.0.0.1 means “this PC”. Use the address of the PC running the HUD when the game runs on a console or on another machine.
Port: A number that tells the receiving PC which program should get the packets. The game and the HUD must use the same one. Common defaults are 20777 for the F1 and DiRT games and 20055 for Forza Horizon.
Packet: One UDP message. A game sends many per second, each carrying a snapshot of the car or the session.
Send rate: How many telemetry packets the game sends per second, in hertz. A higher rate gives a smoother HUD and uses more CPU and network.
Packet format: The layout of the bytes in a packet. Some games change it between versions, so the HUD must read the same format the game sends. See F1 25 and the 2026 Season Pack.
Shared memory: A block of memory the game writes to and other programs can read, with no network involved. Assetto Corsa, iRacing and Le Mans Ultimate use it, and some games need a community plugin to expose it.
OutGauge: A compact UDP dashboard protocol created for Live for Speed. It carries engine, pedals and dash lights, and BeamNG.drive supports it too. See BeamNG.drive OutGauge setup.
Data Out: The name of Forza’s UDP telemetry option, found in the HUD settings. See Forza Horizon 6 Data Out settings.
Plugin: A small add-on, usually a DLL in the game folder, that makes a game publish telemetry it does not send on its own. The truck games and rFactor use one.
Browser source: A streaming-app layer that shows a web page. A HUD served as a local web page can be added to OBS this way.

Engine and drivetrain

RPM: Revolutions per minute of the engine. A HUD usually draws it as an arc or bar that fills toward the limit.
Redline and rev limit: The RPM above which the engine stops gaining power or is cut by the limiter. Many games send it as a maximum RPM value.
Gear: The gear the transmission is in. Reverse and neutral are often sent as special values, so a HUD maps them to R and N.
Boost: The pressure a turbo or supercharger adds, often in psi or bar. Cars without forced induction send zero.
Power and torque: Engine output, in horsepower and newton-metres. Only some games send them as live values.
Shift light: A signal that tells you to change up, based on RPM. Rev lights show it as a row of LEDs that fill as you approach the limit.
Throttle, brake and clutch: Your three pedal inputs, usually sent as a value from 0 to 1 or from 0 to 255. A HUD shows them as bars or a trace.
Steering angle: How far the wheel is turned, from full left to full right. A HUD turns it into a steering-wheel graphic.
ABS: Anti-lock braking. When the system pulses the brakes to stop the wheels locking, some games send a flag so a light can show it.
TC: Traction control. It cuts power when the driven wheels spin, and some games send a flag for it.

Grip, forces and attitude

Slip angle: The angle between where a tyre points and where it travels. Some slip is what makes a tyre grip, and too much means it slides.
Slip ratio: How much a tyre spins faster or slower than the road under it. Positive values mean wheelspin, negative values mean braking slip or a lockup.
Tyre load: The vertical force pressing a tyre on the road. It rises on the outside tyres in a corner and on the front tyres under braking.
Tyre temperature: Some games send the surface, inner and core temperature of each tyre. The surface changes fastest, while the core follows the carcass. Temperature affects grip and wear.
Brake temperature: The heat of each brake disc. Long, hard braking overheats it and can reduce stopping power.
Suspension travel: How far each spring is compressed or extended. It shows weight transfer, bumps and landings.
G-force: Acceleration measured in multiples of gravity. Lateral G is cornering, longitudinal G is braking and acceleration, vertical G is bumps and crests.
Yaw, pitch and roll: The three rotations of the car: yaw is turning left or right, pitch is the nose going up or down, roll is leaning side to side.
Drift angle: The angle between the direction the car points and the direction it moves. A drift HUD uses it to show how sideways you are.
Handbrake: The state of the parking brake, sent as on and off or as a value. Drift and rally HUDs use it.

Race and lap data

Lap time: The time of a lap. Games usually send the current, last and best lap separately.
Lap distance: Metres travelled since the start line this lap. It lets a HUD compare two laps at the same point. Not every game sends it.
Lap delta: Your live time gap to a reference lap, usually your best. Negative means ahead. See Lap delta explained.
Sector: A section of a lap, normally one of three, with its own split time. Sectors show where on the track you gain or lose.
Fuel per lap: The fuel used in one lap, found by watching the tank drop over a lap. Divide the fuel left by it to see how many laps remain.
Pit limiter: A speed cap for the pit lane. Games send a flag that tells a HUD when it is active.
DRS: Drag Reduction System, an F1 rear-wing flap that opens to cut drag and add speed on a straight. The F1 games send its state.
ERS: Energy Recovery System, F1’s hybrid system. The stored energy level is sent, and a HUD shows it as a charge bar.
Driving line: The suggested racing line some games draw on the track. A few send a value that says whether you are on it.
Race position: Your place in the field, as a number. Practice and free-roam sessions may send zero.

Horizon Labs binds HUD layers to these fields in the Designer. Each game’s page lists the fields it sends, and the Designer flags a field a game does not provide. Horizon Labs only reads the telemetry the game sends out.