06 Engine Control
Tuning fundamentals
Load, interpolation, AFR, and the order you actually build a map.
10 min readUpdated 2026-08
A Race Core map is a set of tables the firmware interpolates. You are not typing a pulse width for every RPM. You are teaching the ECU how much air the engine moves (VE), what AFR you want, and how much spark the chamber will take — then letting the maths do the rest. If the basics are wrong, every race function on top of them is noise.
Tune in this order
- 01Trigger. Composite log, offset, stable RPM. Nothing else is real until this is done.
- 02Req-fuel and injector dead-time. These are facts about the hardware, not a tune.
- 03Idle VE and idle spark, hot, in gear if it idles in gear. This is your sanity cell.
- 04Cruise VE and spark. Most of a street or parade-lap map lives here.
- 05Transient (accel enrichment). After VE, not instead of it.
- 06Boost VE and spark, on a dyno or a quiet road, one cell at a time.
- 07Closed-loop AFR, then knock, then idle loop, then race functions (ALS, launch, traction, boost-by-gear).
Do not enable anti-lag, rotational idle or a 2-step on a map that has not idled cleanly. Those strategies assume fuel and spark already make sense.
What “load” means
| Mode | Load axis | Use when |
|---|---|---|
| Speed-density | MAP (kPa) | Turbo, supercharged, or any engine with a usable manifold-pressure signal. The default. |
| Alpha-N | TPS (%) | ITBs, aggressive cams, or MAP that is too noisy at idle. Fuel is then a guess against throttle, not air. |
| SD + Alpha blend | MAP and TPS | ITB turbo or a cam that makes MAP limp at idle and come alive at 3 000 rpm. |
Pick one load story and stick to it. Switching an engine from MAP to TPS halfway through a VE table is how you get a 0.8 AFR hole at the splice. Race Core interpolates between the cells you filled; it does not invent air the sensor did not see.
How a table is read
- The firmware finds the four nearest cells (RPM below/above, load below/above) and interpolates. A spike in one cell bleeds into its neighbours.
- If you never hit a cell, it does not matter what you typed there. Log RPM and load and look at the hit-count / trail, not at a pretty gradient.
- Tune the cell you are in, then the ones you pass through. A 4 000 rpm / 180 kPa pull does not tune 8 000 rpm.
- Do not put a giant number in one cell to “catch” a transient. That is accel enrichment or a PWM table, not VE.
AFR targets
| Region | Petrol (λ) | E85 (λ) | Why |
|---|---|---|---|
| Idle / cruise | 1.00–1.05 | 1.00 | Stoich is efficient and cool. A little lean at cruise is fine if EGTs and drivability hold. |
| Transient / tip-in | 0.90–0.95 | 0.90 | Wet the walls. Closed loop cannot keep up here — that is accel enrichment. |
| Power, NA | 0.86–0.90 | 0.85–0.90 | Best power is richer than stoich. Chasing 14.7 at WOT is how pistons die. |
| Power, boost | 0.78–0.85 | 0.78–0.85 | Fuel is also charge cooling. Leaner is not “more efficient” in the chamber under 1.5 bar. |
Command a target, then make VE hit it. Do not drag VE around because you do not like the target table. If power AFR is 11.5 petrol and you keep commanding 13.0, the wideband will obey you all the way into a melted ring.
Spark, briefly
MBT (minimum spark for best torque) is the ceiling on an NA petrol engine at cruise. Under boost you are not at MBT — you are at “as much as the chamber will take without knock.” Knock control is a backstop, not a tuning method. See Ignition control.
One change at a time
- Change VE or spark or accel, not all three on the same pull.
- Log the pull. Look at it. Then change the cell.
- If AFR and knock and boost all moved, you learned nothing. Lock boost, lock spark, move fuel — or the reverse.
- Weather, fuel and a dirty filter will move AFR. Do not chase a 0.1 AFR on a 35 °C Johannesburg afternoon against a 15 °C morning log without IAT compensation in play.
When to stop
A finished base map idles, cruises without a hiccup, pulls clean to redline on the AFR you meant, and does not knock. Race functions (anti-lag, rotational idle, boost-by-gear, traction, PWM extras) sit on top of that. Adding them earlier just gives you three ways to hide a bad VE table.