Barometric Sensor¶
Reads atmospheric pressure — effectively altitude — and serves as the reference the load calculations are scaled against.
What it is¶
The barometric sensor measures ambient atmospheric pressure. At sea level that's about 101 kPa; it falls as altitude rises. It gives the ECU a fixed reference for "outside" pressure to compare manifold pressure against.
Why it matters¶
- Load reference — MAP is meaningful relative to atmospheric pressure. Barometric is the baseline that distinguishes vacuum from boost and scales the load tables sensibly.
- Altitude / density — thinner air at altitude means less air mass for the same manifold pressure; the speed-density density term uses the baro reference so fuelling stays correct as conditions change.
How to tune it¶
Barometric is a reference input, not something you set. Its value is that it lets a single tune behave correctly across different atmospheric conditions, because load is computed as a ratio to baro rather than an absolute.
Rule of thumb
If a tune that's perfect at sea level runs differently at altitude, the baro reference is doing its job — it's telling the ECU the air is thinner, not that your tables are wrong.
In the game¶
The barometric reading underlies the load and density calculations. It's the steady "atmospheric" baseline behind the MAP gauge's swing.