Glossary of Tuning Terms

An alphabetical list of technical acronyms and tuning terms with brief definitions and explanations.

• Accelerator Pedal Maps

  ECU maps that define the relationship between accelerator pedal position (APS) and requested engine torque or throttle valve angle in electronically controlled diesel engines.

• Aftertreatment Control Module (ACM)

  Aftertreatment Control Module (ACM) is a electronic control unit responsible for managing the diesel aftertreatment system, including the diesel particulate filter (DPF), selective catalytic reduction (SCR), diesel oxidation catalyst (DOC), and related sensors. It works in coordination with the ECM to ensure proper emissions control and regeneration.

• Air Charge Temperature (ACT)

  Air Charge Temperature (ACT) is the temperature of the air entering the engine cylinders after compression and intercooling. Also referred to as AIT (Air Intake Temperature) or CAT (Charge Air Temperature) in diesel engine diagnostics.

• Active Regeneration

  The automatic process by which the diesel particulate filter (DPF) is cleaned by raising exhaust temperatures through post-injection events or other methods. Triggered by soot load thresholds detected by the ACM or ECM.

• Advance Multiplier

  In some diesel ECUs, a factor used to adjust or limit ignition timing advance based on conditions such as load, temperature, or knock control algorithms. More common in systems with pilot/main/post injection phases.

• Air Flow Meter (AFM)

  Air Flow Meter (AFM) is a sensor, often integrated as a Mass Air Flow (MAF) sensor, that continuously measures intake air to assist the ECM in calculating engine load, fuel delivery, and EGR control.

• Air Fuel Ratio (AFR)

  The ratio of air to fuel entering the combustion chamber in a diesel engine. Diesel engines typically run lean, with AFRs ranging from 18:1 to over 40:1 depending on load and operating conditions.

• Air Intake Temperature (AIT)

  The temperature of air entering the intake manifold, used by the ECM for air density calculation and load estimation. Also referred to as CAT or ACT in diesel terminology.

• Automated Manual Transmission (AMT)

  A type of transmission used in many diesel trucks that automates gear shifts and clutch engagement using actuators and the TCU. Common examples include Eaton UltraShift and Allison automatic systems adapted for heavy-duty diesel platforms.

• Accelerator Pedal Position Sensor (APS)

  A sensor that detects the driver's input on the accelerator pedal and sends a signal to the ECM to determine torque request and fueling strategy.

• Calculated AirFlow (CAF)

  In diesel engines, the estimated airflow into the cylinders based on sensor inputs (such as MAP, MAF, or IAT) and correction maps. CAF is critical for calculating engine load, controlling EGR, managing boost, and determining appropriate fuel delivery.

• Controller Area Network (CAN/CANbus)

  A high-speed vehicle communication network standard used in diesel trucks to allow ECUs, sensors, and modules (like the ECM, ACM, and TCU) to exchange data in real time. Essential for emissions systems, diagnostics, and powertrain coordination.

• Charge Air Temperature (CAT)

  The temperature of compressed intake air after the turbocharger and intercooler. Also referred to as ACT (Air Charge Temperature) or AIT (Air Intake Temperature) in diesel engine diagnostics.

• Check Engine Light (CEL)

  A warning light on the dashboard that illuminates when the ECM detects a fault, such as emissions issues, sensor malfunctions, or drivetrain problems. Common in diesel trucks with OBD systems.

• Closed Loop

  A control strategy where the ECM adjusts engine parameters (like fuel delivery or EGR) in real time based on sensor feedback. In diesel systems, this applies to components like NOx sensors, oxygen sensors, and DPF regeneration controls.

• Custom Datalogging

  The ability to record and analyze real-time engine data—including boost, injector timing, DPF status, and fuel trim—from the diesel ECU, using external tuning or diagnostic tools.

• Custom Gauge

  A dashboard display that shows data from the diesel ECU or custom tuning maps—such as boost pressure, EGT, AFR, or DPF regen status—depending on the vehicle and gauge integration system.

• Custom Maps

  User-defined calibration tables in the ECU that alter factory diesel parameters such as injection timing, torque limiters, EGR behavior, and boost control to improve performance or efficiency.

• Checksum Verification Number (CVN)

  A checksum stored in the ECM to verify the integrity of calibration or firmware files. Used in diesel systems to detect unauthorized tuning or file corruption during diagnostics.

• Diesel Exhaust Fluid (DEF)

  A non-toxic, urea-based solution injected into the exhaust system of diesel engines as part of the Selective Catalytic Reduction (SCR) process. DEF reduces nitrogen oxide (NOx) emissions by converting them into nitrogen and water vapor.

• Drive By Wire (DBW)

  An electronic throttle system used in many modern diesel engines, where the accelerator pedal sends an electronic signal to the ECM rather than using a mechanical linkage.

• Direct Injection or Direct Injector (DI)

  A fuel injection method in which diesel fuel is injected directly into the combustion chamber. It is standard in modern diesel engines for increased power and efficiency.

• Diagnostic Box

  A diagnostic interface device (such as a NEXIQ or DLA+) used to connect diesel vehicles to a diagnostic computer. Enables reading and writing ECU data, troubleshooting DTCs, and performing resets or reprogramming.

• Diesel Particulate Filter (DPF)

  A filter located in the exhaust system that captures and stores soot (particulate matter) from diesel combustion. It requires periodic regeneration to burn off accumulated soot and maintain performance.

• Diesel Oxidation Catalyst (DOC)

  An emissions control device in diesel exhaust systems that uses a catalyst to convert carbon monoxide (CO) and unburned hydrocarbons (HC) into carbon dioxide (CO₂) and water (H₂O).

• Diagnostic Trouble Code (DTC)

  A standardized code stored in the ECM when a malfunction or abnormal condition is detected in the diesel engine or emissions system. Used for troubleshooting and repairs.

• Engine Control Module (ECM)

  The main computer that manages all critical functions in a diesel engine, including fuel injection, emissions controls, boost management, and diagnostics. Interchangeable with ECU in most diesel contexts.

• Engine Coolant Temperature (ECT)

  A sensor input monitored by the ECM to regulate engine warm-up, fan operation, fuel delivery, and emissions in diesel engines.

• Engine Control Unit (ECU)

  Also known as the ECM in diesel engines, this module monitors and adjusts critical engine parameters such as fueling, turbo boost, EGR, and emissions to ensure efficiency and compliance.

• ECU Flashing

  The process of rewriting the ECU's firmware or software to modify engine parameters, improve performance, or add new features. This is typically done using specialized tuning software and hardware.

• Exhaust Gas Recirculation (EGR)

  Exhaust Gas Recirculation

• Engine Load

  AirFlow divided by engine RPM; effectively how much air enters the engine per revolution. It may be expressed as a percentage of cylinder fill

• End of Injection (EOI)

  Stipulated as an angle, in degrees

• Electronic Stability Program (ESP)

  Also Dynamic Stability Control, is onboard computer technology that improves vehicle stability by detecting loss of traction or steering control and intervening to correct it via the antilock braking system and engine control

• Equivalence Ratio

  The desired closed-loop AFR that the management ECU attempts to meet

• Fail Safe

  A device or function attribute that, in the event of a specific type of failure, responds in a way that minimises or negates harm to other devices or persons

• FastFlash

  Rapid system of ROM programming by block, where all code is built into the ECU

• Forced Induction (FI)

  Boosted air charge, as with supercharging and turbocharging

• FlexFuel (Also Dual Fuel)

  Refers to an engine capable of running on more than one type of fuel—such as diesel and biodiesel—sometimes mixed in the same tank.

• Front Mounted Intercooler (FMIC)

  Front Mounted Intercooler

• Fuel Pulse Width (FPW)

  The duration of opening of each injector in milliseconds (ms)

• Fuel Trim (FT)

  A system-integrated ability to automatically make small adjustments to fuel metering to compensate for certain factors affecting engine operation

• Fuel Trim Long Term (FTLT)

  Fuelling compensation applied on long-term basis

• Fuel Trim Short Term (FTST)

  Fuelling compensation applied on short-term basis

• Gauge Hijack (see also Custom Gauge)

  The temporary reassignment of certain dashboard instruments via software in order to display other functions such as AFR, Boost, Fuel Trims or Map Switch modes

• Hybrid Speed Density

  A programmable function that allows switching between MAP and MAF airflow sensing for the Engine Load calculation depending on operating conditions

• Hysteresis

  A slight margin for variation, or 'cushion zone', particularly with reference to a predetermined rev limit

• Idle Learning

  A program feature that balances idling parameters - particularly on a dual-intake system such as that of the Nissan GT-R

• Intake Manifold Runner Control (IMRC)

  Or Intake Manifold Swirl Control (IMSC), a vacuum and solenoid-actuated system that partially closes an intake duct to generate intake air turbulence under low-power running

• Intake Manifold Swirl Control (IMSC)

  Or Intake Manifold Runner Control (IMRC), a vacuum and solenoid-actuated system that partially closes an intake duct to generate intake air turbulence under low-power running

• Injector Scaling

  The recalibration of fuel injector characteristics (parameters such as flow rate, pulse width etc) to suit engine modifications

• Intercooler Spray System (ISS)

  A coolant-spraying mechanism that maximises intercooler efficiency and is used on a few high-performance turbocharged cars

• K-Factor

  A Nissan-specific multiplier for the manufacturer's base fuel schedule - a figure best left unchanged

• K-Line

  A pre-CANbus communications data-transmission line and protocol still occasionally used in conjunction with a CANbus

• Knock

  An abnormal combustion event where the air-fuel mixture ignites prematurely or unevenly, causing sharp pressure spikes that can damage the engine. Often audible as a metallic pinging sound.

• Knock Correction

  The amount of ignition timing correction (positive or negative) set by the ECU in response to cylinder knock, or its absence

• Knock Retard

  The amount of ignition timing retardation set by the ECU in response to detected cylinder knock

• Lambda

  The air-fuel equivalence ratio, which compares the actual air-fuel ratio (AFR) to the stoichiometric AFR—the ideal ratio for complete combustion.

• Lambda Sensor (O2 Sensor)

  A sensor that monitors the oxygen content in exhaust gases to help optimize combustion and emissions. Used in both diesel and gasoline engines.

• Launch Control

  An electronic aid - effected via a number of management functions - that assists drivers of both racing and street cars to accelerate cleanly (ie with minimal wheelspin) from a standing start

• Limp-Home

  A reduced-performance mode of engine operation adopted by the management system when certain engine faults are detected

• Live Data

  Data streamed from the management ECU as the engine is running

• MAF (Mass Air Flow)

  As in MAF Sensor; the amount of air flowing is stipulated in grammes per second (g/s)

• MAF Bank Switching

  A feature that allows airflow measurement correction after the fitting of an aftermarket intercooler that swaps airflow between cylinder banks

• MAP (Manifold Absolute Pressure)

  As in MAP sensor, whose output is stipulated in psi or bar

• Map Switching

  The selection of an alternative engine management map via a 'hijacked' or 're-purposed' control in the car

• Master Tuner

  Master Tuners are the most experienced category of engine tuners (as determined by BanditTuning) and have the authority to purchase Programming Kits and retail them to customers together with their own ECU calibrations

• MBT (Maximum Best Torque/Minimum Best Timing)

  Can also be understood as 'minimum timing advance for best torque'

• MRP (Manifold Relative Pressure)

  Negative or positive inlet manifold pressure relative to atmospheric pressure

• NA (Naturally Aspirated)

  Unboosted, neither turbocharged nor supercharged

• OBD (On Board Diagnostics)

  A general term for a vehicle's self-diagnostic and reporting capabilities; OBD systems give access to the status of the various vehicle sub-systems

• OBD-II (On Board Diagnostics)

  The current OBD standard capable of providing real-time data and a standardised series of diagnostic trouble codes.

• OEM (Original Equipment Manufacturer)

  Most often used by BanditTuning in the context of the manufacturer of the car being modified, and specifically its 'OEM' (factory) engine management maps

• Open Loop Control

  A control mechanism that does not observe the output of the process it controls, but instead computes its input on the basis of current state and its integral model

• Per-Gear Rev Limit

  As the name suggests, different rev limits can be set for individual gears

• Piggybacking

  An undesirable method of tuning whereby various factory-standard engine-management ECU input and output signals are 'hijacked' or manipulated by a third-party device in order to 'deceive' the ECU

• Power Balance

  The disabling of individual fuel injectors to help pinpoint cylinder faults

• ProECU TOOLS (BanditTuning)

  Everything the BanditTuning Tuner needs - hardware, software, licence key and documentation - to successfully tune using ProECU

• ProECU Programming Kit (BanditTuning)

  The hardware and software that Master Tuners purchase from BanditTuning and sell on to retail customers for their own, non-commercial use, together with the relevant vehicle ROM files.

• ProECU Tuning Suite (BanditTuning)

  The vehicle-specific software needed to produce tuned ROM files. Tuning Suites are ‘trade only’ tools that allow ECU calibrations to be altered (for a wide range of tuning requirements) then programmed into the factory ECU using the ProECU Programming Kit

• RaceROM Features (BanditTuning)

  Additional and enhanced features for OEM vehicle ECUs tuned with BanditTuning tuning tools, which bring increased tuning and driving capabilities such as Map Switching, Flat-Foot Shifting, Valet Mode and more. RaceROM features are included in the cost of the relevant Tuning Suite

• RaceROM Feature File (BanditTuning)

  The BanditTuning code and data applied to an ECU ROM file before it is programmed into a vehicle ECU

• RAM (Random Access Memory)

  A type of computer data storage (usually volatile as it needs constant power) in integrated circuit form that allows data to be read or written in almost the same amount of time regardless of its physical location within the memory

• Regional Distributor (BanditTuning)

  A company appointed by BanditTuning to exclusively sell and support BanditTuning products in a specific country or defined territory; receives support directly from BanditTuning

• Regional Sub-Dealer (BanditTuning)

  Receives support from the BanditTuning Regional Tuner chosen to be their 'parent' tuner who provides ROM file calibrations and tuning support, plus any BanditTuning software required

• Regional Tuner (BanditTuning)

  Operating in the specific country or defined territory of the Regional Distributor, the Regional Tuner purchases software, hardware and Flash Licences from, and is supported by, that distributor

• Rolling Cylinder Cut

  The engine management-controlled shutting-off of one or more cylinders in a predetermined sequence to achieve smoother rev limitation - especially in conjunction with Launch Control

• Roll Racing

  In motor sport a moving (rather than standing) start to a race that reduces shock stresses on vehicle components; also an BanditTuning RaceROM feature for the Nissan GTR

• ROM (Read Only Memory)

  A type of non-volatile memory used in computers and other electronic devices in which stored data can be modified only slowly, with difficulty or even not at all

• RaceROM Boost Control (RRBC)

  RaceROM Boost Control

• RaceROM Feature File (RRFF)

  RaceROM Feature File

• Supercharger or Supercharging (SC)

  Supercharger or Supercharging

• SCR (Selective Catalytic Reduction)

  A system that injects a urea-based solution into the exhaust stream to reduce nitrogen oxide (NOx) emissions in diesel engines.

• SD Card

  A small, portable memory card used for storing data, including ECU maps and logs.

• SD Card Reader

  A device that allows reading and writing data to an SD card, often used for transferring ECU maps and logs.

• Soot Accumulation Ratio

  The ratio of soot mass to the total mass of the diesel particulate filter (DPF), indicating how much soot has accumulated and how close the filter is to needing regeneration.

• Speed Density (SD)

  The calculation of engine load from manifold absolute pressure rather than mass air flow

• SD-VE (Speed Density-Volumetric Efficiency based)

  The SD feature changes the way Mass Airflow is calculated: in SD mode the ECU disregards MAF sensor input and calculates Mass Airflow based on Engine Speed, Manifold Pressure and Air Temperature

• Single Turbo

  as opposed to Twin Turbo

• Sub-Dealer (BanditTuning)

  A member of the BanditTuning Tuner network who tunes customer vehicles using ProECU Tools and suitable tuned ROMs provided by a 'parent' BanditTuning Tuner. There are two Sub-Dealer types: those who program only and those who create and edit ROMs using full Edit Software acquired from a parent dealer

• SRM (SynchroRev Match)

  A Nissan name for programmed double-declutching-style throttle 'blips' on gearbox downshifts – otherwise known as Autoblip in BanditTuning-speak

• Turbocharger or Turbocharging (TC)

  Turbocharger or Turbocharging

• Transmission Control Module (TCM)

  Transmission Control Module

• Traction Control System (TCS)

  Traction Control System

• TCU (Transmission Control Unit)

  An electronic control module that manages gear selection, clutch engagement, and shift timing in automated and automatic transmissions. In diesel trucks, the TCU works closely with the ECM to optimize performance, fuel efficiency, and drivability under varying load and terrain conditions.

• Throttle Angle

  The opening angle of the throttle butterfly valve, in degrees

• Throttle Target Max

  The maximum allowed throttle valve opening angle in relation to RPM

• Torque Actual

  The current torque produced by the engine, as calculated from MAF; the amount of torque available irrespective of Torque Demand

• Torque Demand

  The torque demanded by the driver using the accelerator pedal; the driver input

• Torque Monitoring

  The calculation of torque output from predetermined engine management data when there is no direct means of measuring it (ie with a dynamometer)

• Trustful Checks

  Pre-programmed data checks and comparisons built into some ECUs to detect and safeguard against errors, particularly those with road-safety implications

• Tuner

  A business whose facilities and experience are deemed suitable to recalibrate engines with a Delete Kit and Tuning Suites.

• Tuning Suite

  The software required to tune a given car, truck, excavator or tractor.

• Twin Turbo (as opposed to Single Turbo)

  Twin-turbo setups can fall into the two basic categories or parallel operation and series (sequential) operation

• Valet Mode

  An easily enabled low-power mode with torque, speed and distance settings that brings peace of mind when entrusting your vehicle to another person

• VDC (Vehicle Dynamics Control)

  A system based on anti-lock braking that senses a vehicle's loss of grip and impending wayward handling and applies individual brakes and adjusts engine power in order to correct it

• VE (Volumetric Efficiency)

  The efficiency with which intake air is packed into the cylinders, expressed as a percentage - the higher the better

• VTC (Variable Timing Control)

  Adjusts the inlet and/or exhaust camshaft position relative to the current crankshaft position

• VVT (Variable Valve Timing)

  Advances or retards the inlet or exhaust camshaft position relative to the current crankshaft position without changing either cam profile or valve lift

• Wastegate Duty

  The programmed cycling of a solenoid valve that applies positive pressure to the turbocharger wastegate actuator rod in order to control turbo speed

• WG (Wastegate)

  The boost-limiting valve of a turbocharger installation

• WHP (Wheel HorsePower)

  The horsepower produced and measured at the driven wheels

• WTQ (Wheel Torque)

  The torque produced and measured at the driven wheels