VT 275 DESIGN FEATURES Offset Crankpins The 4-stroke engine requires 720° of crankshaft rotation to complete all four strokes of the cycle. In a multi-cylinder engine dividing the 720 degrees by the number of cylinders will equal the ideal crankshaft rotation between combustion events in the firing order. The VT 275 achieves equal spacing of the combustion events by splitting the crankpins and staggering the individual journals 30є. #4 CRANKPIN #3 CRANKPIN Balance Shaft Timing The crankshaft counterweight, flywheel, and damper are used to offset the rotating and reciprocating forces developed in the 90° V6 engine, but these components alone will not offset the couple imbalance.
Couple imbalance is created when two or more forces act on the crankshaft at different points along its length. Couple imbalance, if not offset, results in pitch and yaw forces on the engine that are felt by the vehicle occupants as a vibration. BALANCER SHAFT BALANCER SHAFT COUNTER WEIGHT COUNTER WEIGHT BALANCER SHAFT GEAR BALANCER SHAFT GEAR COUNTER WEIGHTED COUNTER WEIGHTED • Couple imbalance forces in the engine are offset by the balance shaft forces as it rotates at crankshaft speed but in the opposite direction. International ® VT 275 V6 Engine 21