Boost Target Maps and Airflow Requirements ⋆ ECU Remap & Chiptuning Files — DPF, EGR, AdBlue, DTC

🧠 Part of the TuningBot ECU Knowledge Base — in-depth documentation on ECU logic, maps, emissions systems and safe calibration methods.

Boost target maps define the desired intake manifold pressure based on engine operating conditions. These maps are fundamental to airpath control and directly influence achievable power.

Vue d'ensemble

The ECU calculates boost targets based on torque demand, ensuring sufficient airflow for the requested fuel quantity while respecting smoke limits and turbo protection.

Target Map Structure

X-axis — engine speed (RPM)
Y-axis — requested load or torque
Z-value — target boost pressure (mbar absolute or relative)

Boost Target Chain

Driver Wish → Torque Request
         ↓
Airflow Requirement (from torque model)
         ↓
Boost Target (considering altitude, temp)
         ↓
Limiter Checks (turbo speed, EGT)
         ↓
Final Boost Target → PID Controller

Limiting Factors

Turbo speed limit — prevents overspeed damage
Compressor surge line — avoids unstable operation
EGT limits — thermal protection
Atmospheric pressure — altitude compensation
Intake temperature — density correction

Smoke Limiter Interaction

Boost and smoke limiter work together:

Smoke limiter caps fuel based on available air
More boost = more air = higher smoke limit = more fuel allowed
This is why boost must be raised BEFORE increasing fuel

Altitude Compensation

Relative Boost = Absolute Boost - Atmospheric Pressure

At sea level: 2000 mbar absolute = ~1000 mbar relative
At 2000m altitude: 2000 mbar absolute = ~1200 mbar relative

ECUs typically work with absolute pressure, compensating internally.

Temperature Effects

Hot intake air is less dense
ECU may target higher boost to compensate
Intercooler efficiency affects required boost

Calibration Strategy

Identify current boost targets across RPM range
Raise targets progressively (100-200 mbar steps)
Verify turbo speed remains within limits
Check EGT under sustained load
Adjust smoke limiter to utilize additional air

Common Map Types

Boost target vs RPM/load — primary target map
Maximum boost limit — absolute ceiling
Altitude correction — boost adjustment for elevation
Temperature correction — IAT-based adjustment

Best Practices

Log turbo speed when raising boost targets
Higher boost requires supporting modifications at some point
Verify actual vs target boost under load
Transient boost spikes need attention in PID tuning