Dyno Graph

BMEP Pipeline

For each operating point:

m_air  = MAP_abs × VE × Vd / (R_air × T_IVC)
m_fuel = m_air / AFR
Q_in   = m_fuel × LHV_fuel          (actual fuel LHV — not a fixed gasoline reference)
η_ITE  = η_otto × η_comb(λ) × η_timing × RCF
IMEP   = η_ITE × Q_in / Vd
FMEP   = A + B×S_p + C×S_p²         (Chen-Flynn)
PMEP   = max(0, EMAP − MAP_abs)
BMEP   = IMEP − FMEP − PMEP
T      = BMEP × V_total / (4π)
P [hp] = T [Nm] × RPM / 9549

Real-Cycle Factor (RCF)

The RCF is automatically set when fuel type or induction mode changes:

These values are calibrated for use with the actual fuel LHV in Q_in. Override manually after a real dyno pull by adjusting RCF until the simulation matches measured peak HP.

Pull Model

Both NA and turbo pulls start at −10 psig MAP at the map minimum RPM.

A load ramp simulates the absorber building from zero to full braking torque.

For turbo engines, MAP builds via the exhaust enthalpy spool model at each 5 ms step.

The wastegate holds boost at its setpoint once reached.

Friction MEP (Chen-Flynn)

FMEP [bar] = A + B × S_p + C × S_p²

Where S_p is mean piston speed in m/s. Coefficients:

• A ≈ 0.80 bar (constant term, bearing loads)
• B ≈ 0.05 bar·s/m (viscous losses)
• C ≈ 0.0015 bar·s²/m² (inertial losses)