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MAP — Manifold Absolute Pressure

The pressure in the intake manifold, in kPa. It's the primary load signal — the vertical axis of almost every table.

What it is

The MAP sensor reads the absolute pressure inside the intake manifold in kilopascals (kPa). At idle the throttle is nearly closed and the engine pulls a strong vacuum, so MAP is low (well below atmospheric). At wide-open throttle MAP approaches barometric; under boost it climbs above it. In short, MAP is a direct read of engine load.

Why it matters

MAP is the backbone of the speed-density approach:

  • It's the load axis for the VE, lambda, and timing tables — the cell the ECU looks up depends on MAP.
  • It drives the air-density term in speed-density: more pressure means more air mass.
  • Its rate of change triggers acceleration enrichment — a fast MAP rise means a throttle tip-in.

A wrong MAP reading throws off fuel and spark at once, because both read from it.

How to tune it

MAP isn't tuned — it's an input you read. Use it to know which table cell you're in, and to confirm load is doing what you expect (low at idle, high at WOT, boosted under forced induction).

Rule of thumb

When tuning a specific cell, hold the engine at the RPM and MAP that select it — otherwise you're editing a cell the engine isn't actually using.

In the game

The MAP gauge is one of the primary readouts. Watch it swing low at idle and climb toward (or past) atmospheric under load.