ECU tuning glossary

ECU remapping, also called chiptuning, is changing the calibration maps in a vehicle’s engine control unit so the engine behaves differently, for example with more torque, a sharper throttle response or lower fuel use.

The tuner reads the original software from the ECU, edits maps such as boost pressure, injection quantity and ignition timing, and writes the modified file back.

In a file service portal, the customer uploads the original read with the vehicle and the tuning options, and the tuner returns the modified file through the same request.

An ECU (engine control unit) is the computer that runs an engine: it reads sensors such as air mass, boost pressure and coolant temperature and controls injection, ignition, boost and the emission systems through calibration maps stored in its memory.

A modern vehicle has many control units; in tuning, ECU usually means the engine control unit, while the gearbox unit is called the TCU.

The ECU family and its software version decide which tool and which reading method can read it.

EDC17 (Electronic Diesel Control 17) is a family of Bosch engine control units for diesel engines, fitted to many passenger cars, vans and commercial vehicles.

Variants carry a suffix such as C46 or CP14, and the variant decides which reading method works: many can be read over OBD-II, others need a bench or boot connection.

On a file request the ECU type is part of the vehicle data the customer sends, so the tuner knows the family before opening the file.

A checksum is a value the ECU calculates over its software and calibration data to check that the memory content is intact.

When maps are changed, the stored checksum no longer matches, so it has to be recalculated before the file is written back; otherwise the ECU may report a memory fault and refuse to start the engine.

The correction is made by the tuner’s editing software or reading tool. A file service portal carries the corrected file to the customer; it does not calculate checksums itself.

Stage 1 is a software-only remap for an otherwise standard vehicle: the tuner changes the calibration maps and no parts are replaced.

It adjusts parameters such as boost pressure, injection and ignition timing within the limits of the standard hardware.

In a portal, Stage 1 is usually one of the tuning options the customer selects on the file request, priced as its own package.

Stage 2 is a remap written for a vehicle with hardware upgrades, typically to the intake, the intercooler or the exhaust, which let the engine breathe better and stay cooler at higher output.

Because the file depends on the parts fitted, the customer lists them on the request so the tuner can calibrate for that hardware.

OBD-II (on-board diagnostics) is the standard diagnostic port and protocol set of a vehicle, mandatory on new cars in the US from the 1996 model year; the European version, EOBD, followed for petrol cars in 2001 and diesel cars in 2004.

Many ECUs can be read and written through this port without being removed. Where OBD-II access is locked or not supported, the tuner reads the ECU on the bench, connected directly on a desk, or in boot mode, usually with the unit opened.

On a file request, the customer selects the read method, such as OBD, bench, BDM or boot, and the reading device, and both are saved with the request.

A DPF (diesel particulate filter) is a filter in the exhaust of a diesel engine that traps soot and burns it off during regeneration at high exhaust temperature.

Frequent short trips can stop a regeneration from finishing, so the filter clogs, back pressure rises and the ECU may limit power.

On a road vehicle the answer is diagnosis and repair: reading the fault memory and live data, finding the cause and cleaning or replacing the filter. Removing or disabling a DPF on a vehicle used on public roads is illegal in the EU, the UK, the US and most other markets.

EGR (exhaust gas recirculation) sends part of the exhaust gas back into the intake to lower the combustion temperature and reduce nitrogen oxide (NOx) emissions.

The EGR valve and cooler collect carbon over time, which can cause rough running, fault codes and limp mode.

On a road vehicle the fix is cleaning or replacing the parts and finding the cause. Disabling EGR on a vehicle used on public roads is illegal in the EU, the UK, the US and most other markets.

SCR (selective catalytic reduction) is a diesel exhaust system that injects AdBlue, a urea solution, into the exhaust so a catalyst can turn nitrogen oxides (NOx) into nitrogen and water.

Crystallised fluid, a failed pump or heater or a faulty NOx sensor can bring warnings, limp mode and, on many vehicles, a restart block once a countdown runs out.

On a road vehicle the system is repaired, not removed: removing or disabling AdBlue/SCR on a vehicle used on public roads is illegal in the EU, the UK, the US and most other markets.

An immobiliser is an anti-theft system that lets the engine start only when it recognises a coded key, usually a transponder chip in the key checked by the ECU or a separate immobiliser unit.

When an ECU is replaced or cloned, its immobiliser data has to match the vehicle again, which workshops do with key programming or cloning tools.

A file service portal does not change immobiliser data; it carries the file and the request.

Injector coding is entering the correction code printed on each diesel injector into the ECU, so the engine control unit can compensate for that injector’s small manufacturing differences in fuel delivery.

It is needed after an injector is replaced; with wrong codes the engine can run rough, smoke or set fault codes.

Workshops code injectors with a diagnostic tool; it is a separate step from remapping the calibration.

A tuning file service is a business that receives original ECU reads from workshops or dealers, writes the modified calibration and sends the finished file back.

The work runs through a portal: the customer uploads the read with the vehicle, the ECU, the reading device and the tuning options, pays with credits and downloads the result when the tuner has finished.

ECU Tuning Portal is software for running such a service under your own brand; it does not write tuning files itself.

MED17 is a family of Bosch engine control units for direct-injection petrol engines, the petrol counterpart of the EDC17 diesel family.

Variants carry a suffix such as MED17.1 or MED17.5, and as with EDC17 the variant decides whether the unit can be read over OBD-II or needs a bench or boot connection.

On a file request the ECU type is part of the vehicle data, so the tuner can tell a petrol MED17 file from a diesel EDC17 file before opening it.

A master tool is a reading and writing device licensed to a tuner who edits files; a slave tool is a version of the same device sold to a workshop, which reads and writes the ECU but works only with files from its master.

The workshop reads the vehicle with the slave tool and sends the read to its master; the tuner opens it with the master tool, writes the modified calibration and sends the file back for the slave tool to write.

A file service portal carries the read and the finished file between the two; it does not open or convert tool files.