Longitudinal G
The G-force measured along the car's forward-backward axis. Positive longitudinal G indicates acceleration; negative values indicate braking. This channel shows how effectively you are using the car's braking and acceleration capabilities.
Deep dive
Segers defines it precisely in Analysis Techniques for Racecar Data Acquisition: "Longitudinal g-force is the acceleration logged along an axis parallel to the car's centerline (i.e., perpendicular to the lateral g-force). It is basically the acceleration created by the engine's power or the deceleration due to application of the brakes. A positive value is used for acceleration. For deceleration, the sign for the longitudinal g-force is negative." He explains reading the trace: "Maximum braking effort is displayed as the minimum value of the downward dips as the car decelerates." Under braking, a typical HPDE car on street tires generates 0.8-1.2G; under acceleration, 0.3-0.6G depending on power-to-weight ratio.
Sources
- Analysis Techniques for Racecar Data Acquisition
- Data-for-Drivers-PRINT
- Analysis Techniques for Racecar Data Acquisition (Jorge Sergers)(p. 8, 10, 11)