What does the G value mean?
3 Answers
The G in cars is a unit of gravity, with g representing more, mainly gravitational acceleration. During vehicle testing, there are two sets of data: lateral and longitudinal. The lateral data indicates the side-slip limit of the car when turning, commonly understood as the relationship between the vehicle's speed and the angle of the curve without causing side-slip. This represents the vehicle's handling performance. The longitudinal data indicates the vehicle's performance during acceleration and deceleration, i.e., the maximum capacity for speed increase and braking. A car with a higher g value performs better. For general-use vehicles, the maximum and minimum longitudinal values can be achieved, but the lateral values, due to the risk of losing control, are rarely achieved by anyone other than professional drivers. The full vehicle value of a car: This refers to the length and tonnage of the vehicle, charged as a single fee. The vehicle is delivered to a specified location individually, with the fee based on the full vehicle price, equivalent to a charter price. The ECU of a car: ECU (Electronic Control Unit), commonly known as the "onboard computer," is a specialized microcomputer controller for cars, also called the car's dedicated computer. When the engine is running, the ECU collects signals from various sensors, performs calculations, and converts the results into control signals to manage the controlled objects. The inherent program continuously compares and calculates with the signals collected from the sensors during engine operation. The results of these comparisons and calculations control multiple parameters of the engine, such as ignition, idle speed, and exhaust gas recirculation. It also has self-diagnostic and protective functions. The memory continuously records driving data, forming the ECU's learning program to provide optimal control states adapted to driving habits, known as the adaptive program.
Last time at the track day, the coach mentioned G-force, which essentially measures the intensity of the push-back sensation during acceleration or cornering. For example, when braking hard, the force that makes you lurch forward is negative G-force; the push-back feeling during acceleration is called longitudinal G-force; and when cornering, the sensation of being thrown toward the door is lateral G-force. My hot hatch can hit 0.6G during hard acceleration, while my friend's tuned car reaches 1.2G, feeling like a giant hand pressing you into the seat. Normally, exceeding 0.5G while driving can easily cause tire slip, and extra caution is needed in the rain. To improve G-force, start by upgrading to high-grip tires—just modifying the engine without better tires can be dangerous.
As vehicle testers, we measure G-forces daily with professional equipment. Simply put, it quantifies dynamic vehicle loads – stronger braking is indicated by larger negative X-axis values; Y-axis figures reflect anti-roll capability during cornering; acceleration is measured by positive Z-axis peaks. Regular sedans typically reach about 0.8G cornering limits, while supercars can achieve 1.5G. However, high G-forces expose chassis weaknesses: during a recent test of a new model, steering became unstable just beyond 1G, and disassembly revealed undersized anti-roll bars. Tuning requires balancing suspension rigidity with comfort – otherwise daily driving becomes uncomfortably bumpy.
