Log Glossary

The ratio of air to fuel in the combustion chamber. Lower number = richer (more fuel). Higher number = leaner (less fuel).

Another way to measure air-fuel ratio, expressed as a ratio where 1.0 = perfect stoichiometric combustion. Below 1.0 = rich. Above 1.0 = lean.

The ECU's real-time, moment-to-moment adjustment to fueling. Think of it as the ECU saying "right now I need to add a little more fuel" or "right now I need to pull back a little."

The ECU's permanent, learned correction to fueling. Unlike STFT which changes moment-to-moment, LTFT is the ECU saying "over time, I've learned I consistently need to add or remove this much fuel."

Pressurizes fuel to ~2,900+ PSI for direct injection. When it can't keep up with demand, fuel pressure drops and the engine runs lean.

Feeds fuel from the tank to the HPFP. If it can't supply enough volume, the HPFP starves and pressure drops.

What percentage of available time the fuel injectors are open. Above ~85% means the injectors are near maximum capacity.

Fuel pressure in the high-pressure rail feeding the injectors. Dropping under load means the HPFP can't keep up.

The percentage of ethanol in the fuel blend. E0 = pure gasoline, E85 = 85% ethanol. Ethanol has higher octane and burns cooler but requires ~30% more fuel volume.

The boost pressure the tune is requesting. Actual boost should track this closely.

The measured boost pressure in the intake manifold at any given moment.

How hard the ECU is working to keep the wastegate closed and maintain boost. 0% = fully open, 100% = fully closed.

How long it takes the turbo to reach target boost from low RPM. Affected by turbo size, exhaust flow, and wastegate behavior.

When actual boost exceeds target and the wastegate can't bleed enough exhaust to control it. Dangerous at high RPM.

When actual boost pressure exceeds the target. Can be intentional (brief overshoot) or dangerous (wastegate failure, boost creep).

When airflow reverses momentarily through the turbo compressor during a sudden throttle lift at boost. Causes fluttering and turbo wear.

Air pressure measured inside the intake manifold, downstream of the throttle body. This is the pressure the engine actually breathes.

Boost pressure measured between the turbo compressor outlet and the throttle body. The turbo's direct output before any throttle restriction.

The percentage difference between actual boost pressure and the ECU's requested target, measured after the turbo has fully spooled.

The turbo building up to target boost pressure from idle or cruise. During spool, boost is low, WGDC is high, and deviation from target is large. All completely normal.

How many degrees before the piston reaches top dead center the spark fires. More advance = more power, but too much causes knock.

When the ECU detects detonation (uncontrolled combustion), it pulls ignition timing to protect the engine. Any amount above 0 degrees means knock was detected.

Uncontrolled combustion where the air-fuel mix ignites from pressure/heat instead of the spark plug. Causes knock and can destroy engines.

When combustion fails in a cylinder. Caused by spark, fuel, or compression issues.

The difference in average knock retard between the cylinder with the most knock and the cylinder with the least. A large spread isolates the problem to a specific cylinder.

The temperature of air entering the engine. Hotter air = less dense = less power and more knock risk.

Engine coolant temperature. Monitors the health of the cooling system under load.

Engine oil temperature. Oil breaks down at high temperatures, reducing its ability to protect engine internals.

When repeated hard use causes temperatures to build up faster than the cooling system can dissipate.

When the DME reduces power output because temperatures have exceeded safe thresholds. Manifests as throttle closure or reduced boost target.

How effectively the intercooler cools compressed air. 100% = ambient temp, 0% = no cooling.

Temperature of exhaust gases. Extremely high EGT indicates lean fueling, excessive timing, or insufficient cooling.

The amount of torque the driver is requesting via the accelerator pedal.

Internal ECU/TCU software caps that prevent the engine from producing more torque than the transmission can safely handle.

When the DME reduces throttle angle even though the driver's pedal is at 100%. Used as secondary boost control to prevent overboost or protect the engine.

A measure of how much air the engine is ingesting relative to capacity.

Digital Motor Electronics: BMW's engine control unit. Manages fueling, timing, boost, and all safety interventions.

Transmission Control Unit. Manages shift points, torque limits, and clutch pressures in the ZF8 automatic.

Wide Open Throttle: 100% accelerator pedal. The condition under which most diagnostic analysis is performed.

A time-series CSV recording of ECU parameters captured during driving. The raw data TBK Logs analyzes.

The ECU uses O2 sensor feedback to actively adjust fueling in real time.

Fueling runs from a fixed map without O2 sensor feedback, typically at WOT under boost.

BMW's variable valve timing system. Adjusts cam timing for optimal performance.

Unintended air escape in the pressurized intake system. Symptoms: can't hit boost target, high WGDC, lean trims.

The combined term for STFT and LTFT: how much the ECU adjusts fueling to hit target AFR.

The percentage of accelerator pedal travel. 100% = wide open throttle (WOT).

The chemically ideal air-fuel ratio (14.7:1 for gasoline). At this ratio, all fuel and oxygen are fully consumed.

A hard cap on the overall health score that activates when safety-critical conditions are detected, regardless of how well other categories score.

A meta-score (0-100) measuring how hard the car was pushed during the log, separate from the health score. Grades: Extreme, Hard, Moderate, Light, Minimal.

The overall engine health rating (0-100) computed from 5 weighted categories: boost, fueling, ignition, drivetrain, and temperatures.

How you use your car: Street, Track, Drag, Drift, or Mixed. This determines how scoring categories are weighted in the health score.

A score (0-100, graded A+ through D) measuring the quality and completeness of the log data: channels present, sample rate, pull duration, data completeness, and multi-pull coverage.

Hardware upgrade recommendations generated from your analysis findings, prioritized by impact, with cost ranges, expected score improvements, and prerequisite dependencies.

The modification level of the ECU tune: Stock, Stage 1, Stage 2, Stage 2+, or Custom. Higher stages run more boost and timing.

A cross-category diagnostic finding that fires when two or more single-category findings correlate, revealing the root cause rather than just listing symptoms.