Engine Geometry & Map Range
Geometry Parameters
| Parameter | Description |
| Bore (mm) | Cylinder bore diameter |
| Stroke (mm) | Piston stroke length |
| Rod Length (mm) | Connecting rod centre-to-centre |
| Static CR | Geometric compression ratio |
Dynamic Compression Ratio
DCR is the actual compression ratio experienced by the trapped charge,
based on the IVC timing using the slider-crank equation:
DCR = (V_eff_stroke + V_clearance) / V_clearance
Where V_eff_stroke is the piston displacement from IVC to TDC.
A later IVC (e.g. 55° ABDC) gives a lower DCR than the static CR.
Map Range
The RPM and MAP axes define the grid of operating points calculated.
- MAP min: typically -14.7 psig (hard vacuum) to 0 psig
- MAP max: 0 psig for NA engines; boost pressure for forced induction
- Grid size: (RPM steps) × (MAP steps) cells