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Lambda (λ)

A dimensionless ratio describing the relationship between the actual air–fuel ratio and the stoichiometric air–fuel ratio required for complete combustion. Lambda values below 1 indicate rich operation, while values above 1 indicate lean combustion, with direct implications for emissions and efficiency. Lambda is continuously monitored by engine management systems to enable closed-loop fuel control and optimal catalyst performance. See: Air–Fuel Ratio and Emissions

Lateral Acceleration

The acceleration acting perpendicular to the direction of travel during cornering, typically expressed relative to gravitational acceleration. It is generated by tyre lateral forces and limited by tyre–road friction and suspension geometry. Lateral acceleration is a primary metric for vehicle handling assessment and stability system calibration. See: Vehicle Dynamics Fundamentals

Leaf Spring

A suspension component formed from stacked metal leaves that support vehicle load and locate the axle. Leaf springs may provide both vertical compliance and axle location depending on configuration. They are widely used in commercial vehicles due to durability, simplicity, and load capacity. See: Suspension Types

Lift Coefficient

A non-dimensional aerodynamic parameter relating lift force to speed, air density, and reference area. It enables aerodynamic comparison independent of vehicle size or operating speed. In automotive design it is used to assess high-speed stability and tyre loading. See: Automotive Aerodynamics

Limited Slip Differential

A differential that limits excessive speed difference between driven wheels under unequal traction. Torque biasing may be achieved through mechanical, viscous, or electronic means. Limited slip differentials improve traction, stability, and controllability. See: Differential Types

Linear Velocity

The rate of change of position along a straight path, typically expressed in metres per second. It links rotational motion of drivetrain components to vehicle road speed. Linear velocity is fundamental to braking, driveline, and wheel slip analysis. See: Vehicle Motion Parameters

Load Path

The engineered route through which forces are transmitted through the vehicle structure. Effective load paths reduce stress concentrations and structural deformation

Load Transfer

The redistribution of normal forces between tyres during acceleration, braking, or cornering. It depends on vehicle mass, centre of gravity height, track width, and wheelbase. Load transfer directly affects tyre grip and handling balance. See: Weight Transfer in Vehicles

Lock-Up Clutch

A mechanical clutch within a torque converter that directly couples input and output. It eliminates hydrodynamic slip under defined operating conditions. Lock-up clutches improve efficiency and reduce heat generation. See: Torque Converter Operation

Longitudinal Dynamics

The study of vehicle motion in the direction of travel, including acceleration and deceleration. It considers powertrain, braking, tyre forces, and resistive loads. It underpins performance assessment and control system design. See: Vehicle Dynamics Fundamentals

Lubricant Viscosity Index

A measure of how lubricant viscosity changes with temperature. Higher values indicate more stable viscosity across operating conditions. It is critical for wear protection, efficiency, and cold-start performance. See: Lubricant Properties

Lubrication System

The system supplying lubricant to moving components to reduce friction and wear. It also assists with cooling, sealing, and corrosion protection. Effective lubrication is essential for durability and reliability. See: Engine Lubrication Systems