Boost Pressure
Displays turbocharger or supercharger boost pressure in real time. The value is calculated as a relative pressure — MAP minus barometric pressure — where positive means boost and negative means vacuum. Three display styles are available: Text, Gauge, and Bar. In Gauge mode, a single needle sweeps from vacuum to the red zone.
1.Overview
The boost widget uses OBD-II PID 0x0B (intake manifold absolute pressure, or MAP) to calculate and display current boost status in real time. If the vehicle doesn't support this PID, the widget won't appear in the selection list.
It's useful on turbocharged and supercharged vehicles, but even naturally aspirated (NA) cars can benefit: the reading stays negative, but you can observe how manifold pressure changes with throttle input. At wide-open throttle, it climbs toward 0 bar; at idle, it sits around −0.6 bar.
| Required PID | 0x0B (MAP: intake manifold absolute pressure) |
| Availability | Vehicles supporting PID 0x0B only (hidden otherwise) |
| Display styles | Text / Gauge / Bar |
| Slot sizes | Text: all / Gauge: Medium & Large / Bar: Wide & Tall |
| Units | bar / kPa / PSI |
2.Calculation
Boost pressure is the difference between MAP and barometric pressure. Simple formula, but the accuracy of the barometric reading directly affects the result.
Boost (bar) = (MAP − Barometric Pressure) ÷ 100
| Variable | Source | Unit |
|---|---|---|
| MAP (manifold absolute pressure) | OBD-II PID 0x0B | kPa (0–255) |
| Barometric pressure | OBD-II PID 0x33 / fallback 101 kPa | kPa |
How to read the value
| State | Example | Meaning |
|---|---|---|
| Positive (+) | +0.80 bar | Turbo is making boost |
| Near zero | 0.00 bar | About equal to atmospheric (NA wide-open throttle) |
| Negative (−) | −0.60 bar | Throttle partially closed (vacuum) |
3.Barometric pressure
Since boost is a difference from atmospheric pressure, the barometric reading matters. The app polls PID 0x33 (Barometric Pressure) every 60 seconds. Vehicles that don't support it fall back to 101 kPa (standard sea-level pressure).
In Gauge style, the current barometric pressure is shown at the bottom-right as "Baro: XXXkPa", so you can check at a glance whether it's reading correctly.
| PID | 0x33 (Barometric Pressure) |
| Polling interval | Every 60 seconds |
| Fallback | 101 kPa (standard sea-level) |
| On-gauge display | "Baro: XXXkPa" at bottom-right |
Vehicles that don't support PID 0x33 always use the 101 kPa fallback. At high altitude (e.g. 1000 m ≈ 90 kPa), boost values will read higher than actual because the assumed baseline is too high.
4.Display styles
Three display styles are available. Which ones you can pick depends on slot size.
| Style | Slot sizes | Key feature |
|---|---|---|
| Text (default) | All sizes | Simple numeric readout with icon |
| Gauge (analog meter) | Medium & Large | Needle gauge from vacuum through boost |
| Bar | Wide & Tall | Positive/negative bar from a zero baseline |
Gauge style
A 270° arc gauge with −1.0 bar (vacuum) at the left and the user-set maximum (default 2.0 bar) at the right. The 0 bar mark sits partway along the arc, acting as the atmospheric baseline.
The needle is smoothed so it tracks changes without jumping. The arc turns warning-red beyond the alert threshold.
| Arc | 270° |
| Minimum | −1.0 bar (fixed) |
| Maximum | User-configurable (default 2.0 bar) |
| Center readout | Current boost + unit |
| Bottom-right | "Baro: XXXkPa" (current atmospheric pressure) |
| Warning zone | Arc turns red above alert threshold |
Bar style
A bar centered on zero: positive pressure extends right (Wide) or up (Tall), negative extends the opposite way. The bar turns warning-red when it crosses the alert threshold.
5.Units
Change the display unit in Detail Settings. The value is stored internally in bar and converted only for display.
| Unit | Conversion | Decimals | Common in |
|---|---|---|---|
| bar | Base unit | 2 | Japan, Europe |
| kPa | 1 bar = 100 kPa | 0 (integer) | SI / academic |
| PSI | 1 bar ≈ 14.5 PSI | 2 | US, UK |
6.Detail Settings
In the slot's Detail Settings tab, you can change the display style, unit, gauge maximum, and warning threshold.
| Setting | Range | Default | Notes |
|---|---|---|---|
| Display style | Text / Gauge / Bar | Text | Restricted by slot size |
| Unit | bar / kPa / PSI | bar | Conversion at display time only |
| Meter range (max) | 1.0–3.0 bar (0.5 steps) | 2.0 bar | Upper limit for gauge and bar |
| Warning threshold | 0.5–2.5 bar (0.1 steps) | 1.5 bar | Triggers warning color |
The warning threshold is always set in bar, even if the display unit is kPa or PSI.
7.Playback
During playback of a recorded session, boost is recalculated from the saved raw OBD data. The same gauge, bar, and text visuals are reproduced.
| Item | Live | Playback |
|---|---|---|
| Data source | OBD-II real-time | Recalculated from saved raw data |
| Barometric pressure | PID 0x33 / fallback | Value from the recording session |
| Update rate | Polling-dependent | Follows playback speed |
8.Tips
Typical boost ranges by vehicle
| Vehicle type | Typical boost |
|---|---|
| Kei car turbo (Japan) | 0.5–0.8 bar |
| Common turbo | 0.7–1.2 bar |
| Sports turbo | 1.0–1.8 bar |
| Tuned / modified | 1.5–3.0+ bar |
| NA (naturally aspirated) | Always negative (−0.2 to −0.8 bar) |
NA cars can still use this widget. Boost stays negative, but you can watch manifold pressure change with throttle input: near 0 bar at wide-open throttle, around −0.6 bar at idle.
Gauge range tips
- Daily turbo: set the max to 1.5 bar — keeps the scale readable.
- Track use: set the max to actual peak boost + 0.5 bar, so you can read fluctuations near the peak clearly.
- NA cars: drop the max to 1.0 bar to make better use of the vacuum range.
Warning threshold tips
- Stock turbo: set it to stock boost limit + 0.1–0.2 bar to catch overboost early.
- Boosted / tuned: set it to your target boost value.
- NA: not needed (it'll never go positive).
Picking a style
| Style | Best for |
|---|---|
| Gauge | Track or spirited driving — maximum visibility. Use a Medium or Large slot. |
| Bar | Compact alongside other data. Works in Wide or Tall slots. |
| Text | Quick glance in a Small slot. |
9.FAQ
Boost isn't in the widget list.
Your vehicle doesn't support PID 0x0B (MAP). Check PID compatibility for your car.
My turbo car shows zero or no movement.
Make sure the engine is running. At idle, the reading should be negative (vacuum). It rises when you open the throttle while driving.
Boost reads too high at altitude.
If your vehicle doesn't support PID 0x33, the app uses 101 kPa (sea-level) as the baseline. At higher altitudes the real pressure is lower, making the calculated boost appear higher.
Is boost useful on an NA car?
Yes. It always reads negative, but you can track manifold pressure changes with throttle input — a useful proxy for engine load.
What happens when the threshold is exceeded?
Visual warning only — the number and gauge turn red. No vehicle controls or audible alerts are triggered.
I switched to PSI but the threshold is still in bar.
By design. The threshold is managed internally in bar and the settings UI always shows bar.
What's "Baro: XXXkPa" on the gauge?
The barometric pressure currently read from the ECU. Vehicles that don't support PID 0x33 will show 101 kPa (the fallback value). Useful for checking accuracy at altitude.
Gauge style is greyed out.
Gauge requires a Medium or Large slot. In Small slots only Text is available; in Wide or Tall slots, Bar is the option.
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