Limiters & Advanced Controls ~7m
Limiters & Advanced Controls
Limiters are maps or constants within the ECU that cap performance or protect the drivetrain. Understanding and adjusting them correctly is crucial for achieving higher power without compromising safety or reliability. This module also introduces advanced control features like launch control and anti‑lag.
🚦 Common Limiter Types
| Limiter Type | Purpose |
|---|---|
| Torque limiter | Caps requested torque by gear or RPM |
| Boost limiter | Restricts maximum turbo pressure |
| Speed limiter | Limits vehicle top speed |
| Fuel cut limiter | Cuts fuel at rev limit or under fault |
| Gear‑specific limiter | Adjusts torque per gear to protect the drivetrain |
Why They Exist
Limiters keep engines and drivetrains within their safe operating ranges. Simply raising one limiter without adjusting others can cause the ECU to invoke a different limiter—or worse, damage hardware.
🧠 Stacking & Interplay
Most ECUs use multiple limiters simultaneously. For example:
- Driver request vs. torque limiter: The driver may demand 400 Nm, but the torque limiter map caps it at 350 Nm. You need to raise the limiter if the hardware can safely handle more.
- Torque monitoring vs. gear limiter: Even if you raise the main torque map, a gear‑based limiter may still reduce torque in lower gears to protect the transmission.
- Boost and fuel limiters: Increasing boost without raising fuel and torque limiters may trigger fuel cut or limp mode.
Always analyse all related limiters and adjust them together so that no single limiter becomes the bottleneck.
🎮 Advanced Controls
Some ECUs include extra features you can tune or activate:
- Launch control: Holds RPM at a set point when the clutch is engaged, allowing a controlled launch. Requires careful coordination of spark and fuel.
- Anti‑lag systems (ALS): Keep the turbo spooled between gear changes by injecting fuel and retarding ignition. Effective but stressful on turbos and exhaust components.
- Pop & bang / crackle maps: Command fuel cut and ignition retard on overrun to produce pops. Purely for sound and not recommended for daily use.
- Rev limiter: The maximum engine speed; you can raise it slightly if the hardware can handle it, but be mindful of valve float and oil pressure.
Handle with Care
Advanced features like launch control and anti‑lag add significant stress to engines and drivetrains. They should only be used when supporting hardware (clutches, turbos) and tuning knowledge are in place.
🔍 Finding Limiter Maps
You can locate limiter maps using the Map Finder or Map Viewer tools:
- Search for flat regions: Limiters often appear as tables with flat or stepped values, e.g., 350 Nm across several RPM points.
- Use known axis values: Limiters frequently use simple axes such as RPM vs. gear or RPM vs. speed.
- Load profiles: If available, load a map profile for your ECU to see labelled limiters.
- Cross‑reference multiple maps: After raising a torque limiter, check other related limiters (like torque monitoring and boost limiters) to ensure consistency.
Incremental Adjustments
Raise limiters gradually and test. Jumping directly to a very high torque or speed limit may expose weak links in the drivetrain or fuel system.
✅ Key Takeaways
- Limiters cap torque, boost, speed and engine speed for safety and reliability.
- Multiple limiters stack together; raising one may not be enough if others remain stock.
- Advanced controls like launch control and anti‑lag provide extra performance but stress hardware.
- Use Map Finder/Viewer and profiles to locate limiter maps and adjust them cautiously.
Next you’ll learn how to handle diagnostics and DTCs in practice, including when and how to disable fault codes.
What happens if you raise the main torque map but leave a gear‑specific limiter unchanged?
Which limiter controls the maximum turbo pressure?