Turbocharger

Compressor Map Model

Efficiency is modelled with an elliptical Gaussian centred on the peak efficiency point:

η(W, PR) = η_peak × exp(-[(W−W0)/σW]² − [(PR−PR0)/σPR]²)

Surge boundary: W_surge = SurgeIntercept + SurgeSlope × PR

Turbine Back-Pressure (EMAP)

Turbine inlet pressure is estimated from the energy balance:

P_comp [kW] = ṁ_air × Cp_air × (T2c − T1c)
EMAP / Patm = ER_turbine  (solved iteratively from power balance)

Dyno Spool Model

At each 5 ms timestep of the dyno simulation:

P_turbine    = ṁ_exh × Cp_exh × T_exh × η_turbine × √(0.83/A_R)
P_compressor = ṁ_air × Cp_air × (T2c − T1c) / η_mech
dMAP/dt      = 0.0373 × max(0, P_turbine − P_comp) × loadFrac

Twin Turbo

In parallel twin-turbo configuration, each compressor sees half the engine airflow.

The operating point on the compressor map shifts left by 2×.

EMAP is the same as single (each turbine also sees half the flow).