Datalog

A time-series recording of engine sensor and ECU parameters captured during driving, used to diagnose and refine a tune.

A datalog is a recorded stream of engine and ECU parameters captured over time while the vehicle runs, the raw evidence behind every tuning decision. Typical channels include RPM, MAP/MAF, commanded and actual AFR (wideband), spark advance, knock retract, fuel trims, coolant and intake temps, throttle position, and boost. You drive through the conditions you want to tune, cruise, wide-open-throttle pulls, idle, then analyze the data to see how the engine actually behaved versus what the calibration commanded. Datalogging is the safety backbone of tuning: you watch for knock, lean spikes, and runaway trims before pushing further, and you always log a wideband before adding boost. In HP Tuners this happens in VCM Scanner, where you build a channel layout, hit record, then review charts, histograms, and tables. Scanner logs feed directly back into VCM Editor table edits, often via overlay or comparison against commanded values.