OBD Gear Indicator

REQUIRED HARDWARE: This app needs a Bluetooth LE (BLE) ELM327-compatible OBD-II adapter. The adapter is sold separately and is NOT included. Without one the app cannot read your vehicle. Classic Bluetooth (SPP) and Wi-Fi adapters do not work on iOS.

BUILT FOR PRACTISING HEEL-AND-TOE
Rev-matched downshifting is normally learned by feel: nothing in the car tells you what engine speed the lower gear actually wants. OBD Gear Indicator calculates it and shows it live, so you practise against a number instead of a guess.

When a downshift becomes possible, a bar appears with the engine speed the next lower gear needs at your current road speed. Blip the throttle, watch the marker slide toward the centre, and release the clutch when it turns green. The target is recalculated continuously while you brake, so it follows the speed you are actually at.

- A number instead of a guess. You learn what 4,200 rpm at 60 km/h in third actually feels like.
- Smoother downshifts. Matching the engine to the gear removes the driveline shock, and the mid-corner upset a mismatched clutch release causes.
- Less wear. Every mismatched downshift is absorbed by the clutch. Matching first means the clutch is not used as a brake.
- Adjustable tolerance. Decide how close counts as matched: a tight band for practice, a wider one for everyday driving.
- Switch it off and check yourself. Practise with it, then turn it off and see how close you still get.

DISPLAY
- Large gear number in the centre of the screen, sized automatically to the space available
- 12-segment RPM LED bar with a configurable start and full-scale engine speed
- Longitudinal G bar showing acceleration and braking in real time, with peak values held briefly
- Portrait and landscape layouts
- Four gear number typefaces (Analog, Racing, 7-segment, 14-segment) and six colours
- Plain black screen designed to be read at a glance; the display stays awake while in use

TWO WAYS TO KNOW THE GEAR
- Auto learning: start at a standstill so the idle speed is recorded, then shift up in order, holding a steady speed for ten seconds in each gear. The app learns each gear's RPM-to-speed ratio and keeps it on the device. Learned values and the per-gear detection window can be edited by hand.
- Enter gear ratios: type in the transmission ratios, final drive ratio and tyre circumference instead. No learning drive needed.

DEMO MODE
Demo mode runs the gear number and the RPM LEDs with no adapter and no vehicle. The G bar still follows your device's real motion.

PRICING
Free to download. The gear display is free. A one-time US$4.99 purchase adds the RPM LED bar, rev-match indicator and G-force bar. Not a subscription. Demo Mode stays free.

HOW IT WORKS, AND WHAT IT CANNOT DO
This app estimates the current gear from engine RPM, vehicle speed and throttle position read over OBD-II. It does not read gear position directly from the vehicle or the gearbox. Because it is an estimate, the gear shown can be wrong while the clutch is disengaged or when sensor conditions are poor.

OBD-II communication itself adds at least about 50 milliseconds between reading the vehicle and drawing the screen. Any delay beyond that comes from the adapter, and ELM327-compatible products vary enormously: an adapter with high response latency will visibly increase both the lag and the error in what is displayed. If the gear reading feels slow or unstable, the adapter is the first thing to change.

The display is reference information only. It never takes priority over the vehicle's own instruments or your awareness of your surroundings. Do not look at or operate the screen while driving; change settings only while stopped.

WHAT YOU NEED
- A Bluetooth LE (BLE) ELM327-compatible adapter, sold separately. A low-latency one is strongly recommended.
- A vehicle with an OBD-II port that reports engine RPM, vehicle speed and throttle position.
- A manual transmission, for the rev-match indicator to be useful.