Acceleration Enrichment¶
A transient squirt of fuel when the throttle is opened quickly, filling the brief lean dip caused by wall-wetting lag.
Demo build: this panel is locked
The enrichment column is available in the full game. See Demo vs Full Version.
What it is¶
When you snap the throttle open, manifold pressure (MAP) rises faster than fuel can follow — some of the new fuel condenses on the suddenly-wetted intake walls, leaving the cylinder momentarily lean. Acceleration enrichment (AE) detects the fast change and adds a short burst of extra fuel to fill that dip. It's the simulator's version of an accelerator pump.
In Engone, AE is shaped by several tunables:
- A rate dead zone (10 kPa/s) below which nothing triggers — so steady driving doesn't enrich.
- An addition curve — how much extra fuel for a given rate of change.
- A duration curve — how long the squirt lasts.
- An ECT scale — colder engines need more (up to 4× when cold), because wall-wetting is worse cold. It scales both the addition and the duration.
The trigger is the strongest of three signals, all on one kPa/s-equivalent scale: the manifold pressure rate, the throttle rate (one throttle-fraction per second is about 100 kPa/s), and the load rate (RPM × MAP rise, which keeps AE alive through a free-rev). It also requires a throttle demand above 2 %.
Defaults (warm):
| Rate (kPa/s) | ≤ 15 | 50 | 120 | 300 | 700 |
|---|---|---|---|---|---|
| Addition | 0 % | 4 % | 10 % | 18 % | 28 % |
| Duration (s) | 0.05 | 0.10 | 0.18 | 0.30 | 0.40 |
| Coolant (°C) | −40 | −20 | 0 | 20 | 40 | 60 | 80+ |
|---|---|---|---|---|---|---|---|
| ECT scale | ×4.0 | ×3.0 | ×2.2 | ×1.7 | ×1.3 | ×1.1 | ×1.0 |
The pulse decays linearly; a new pulse only replaces the running one if it is stronger.
Why it matters¶
Without AE, every fast throttle opening produces a brief lean stumble — a flat spot or hesitation right when you ask for power. Properly tuned, the tip-in is crisp and the mixture stays on target through the transient.
- Too little → a hesitation or stumble on throttle tip-in.
- Too much → a rich "blubber" and a puff of black smoke on tip-in.
The stock tunes have the addition curve at zero, because wall-film compensation already covers transients. With wall-film compensation on, leave AE at zero — a rate-triggered pulse on top of exact compensation is just excess fuel. With it off, AE is needed.
How to tune it¶
Tune with quick throttle stabs and watch measured lambda. If it dips lean on tip-in, raise the addition; if it spikes rich, lower it. Use the dead zone so gentle driving is left alone, and verify the cold scale by repeating the test on a cold engine.
Rule of thumb
Tune AE warm first to get the shape right, then confirm the cold multiplier on a cold engine — cold tip-in needs far more fuel than warm.
In the game¶
FUEL page → right column → ACCEL ENRICHMENT card. Three grids — MAP ROC → ADD,
MAP ROC → DURATION and ECT → AE SCALE — plus a pulse bar, an ACC ROC readout and the live
multiplier.