Inline-Four Engine Cutaway: Crank, Cam and Charge

Show, in one isometric cutaway, how a car engine's four pistons, connecting rods and crankshaft convert reciprocating motion into rotation, and how throttle opening and spark timing change the illustrative air charge and combustion phasing reported by the readout. Cylinder 2's piston-rod-crank linkage and valve events are the single emphasized subject. The apparatus is a generic teaching engine, not a specific production engine or a physically certified instrument.

Generic 1.6-litre-class inline-four, not a specific make or model. Illustrative geometry: 80 mm bore, 80 mm stroke (r = 40 mm), 140 mm connecting rod, 40 cm³ clearance volume and 10 mm maximum valve lift. Fixed cam timing with idealized events: intake open 360–580° of the 720° cycle, exhaust open 140–380°, giving 20° overlap. Firing order is 1-3-4-2 with even 180° firing intervals. Manifold-pressure index is a linear 0.25–1.00 bar proxy; charge is proportional to it; torque index is charge times a Gaussian spark-phasing factor. Friction, pumping losses, heat transfer, fuel dynamics, emissions and knock are not modeled, so the torque index is not a prediction of engine output. Fastener, spring and repeated valve sets are grouped as named assemblies for the 74-part count. All colours are solid four-tone shading; no photographic or measured material is represented.