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Timing Table

The spark-advance map in degrees BTDC across RPM and load — more advance with RPM, less under load.

What it is

The timing table is a 16 × 16 grid of RPM × MAP / load cells, each holding the spark advance in degrees before top dead center (°BTDC). As the engine runs, the ECU looks up the cell at the current operating point and fires the spark that far ahead of TDC.

The table accepts −20° to +40° BTDC (step 0.5°, large step 2°), but the ECU never fires later than 5° BTDC after knock retard and trim, so the effective range is 5°–40°.

The classic shape:

  • Advance climbs with RPM. Flame travel takes a roughly constant time, but at high RPM that time is more crankshaft degrees — so the spark must fire earlier.
  • Advance retards under load. Denser charge burns faster and is far more prone to knock, so high-MAP cells carry less advance.

In Engone the physics also derives timing behavior from RPM, load, compression ratio, octane, and temperature, so the table interacts with the build rather than acting in isolation.

Cranking timing. At cranking speed the ideal is 0–18° BTDC. A table value far outside that makes the engine harder to start — the ignition-catch model penalises it, floored at 20 % (see Starting an Engine).

The stock tune is MBT, but where the engine is knock-limited it sits 6° below the knock limit.

Why it matters

Timing sets how much of combustion's energy becomes torque. The ideal is MBT — the minimum advance for best torque. Fall short and you leave power on the table; overshoot into the knock region and you risk engine damage. The table is where you walk that line.

How to tune it

Build the surface to rise smoothly with RPM and pull back in the high-load cells. Advance toward MBT where octane and conditions allow; keep margin in the high-load cells where knock lives. See Editing Tables.

Rule of thumb

Add advance until torque stops increasing — that's MBT. If torque stops climbing and you hear knock, you've passed the limit: back off.

Watch out

The most dangerous cells are high load / low-to-mid RPM, where cylinder pressure is highest. Be conservative there, especially on low octane.

On a boosted engine

Engone currently simulates naturally aspirated engines only. For background: a boosted engine packs far more air into the cylinder, so the tune changes — target lambda moves richer (to cool the charge and protect against knock), ignition advance comes down in the boosted cells, compression ratio is usually lowered, and higher octane matters more. See Boosted Engines (Background).

In the game

IGNITION page, left. A live tracer dot marks the active cell. The bottom bar shows four values: RPM, MAP, TABLE (the advance your table asks for) and FINAL (the advance actually fired, after knock retard and the engine's global trim — the V8 base, for example, carries a −5° trim). The TIMING readout in the left column shows the final spark too.

The table is editable in the demo build; the panels on its right are not.