Introduction:
With chiptuning, the characteristic maps in the ECU (engine control unit) are adjusted in order to obtain a higher power output or lower fuel consumption (called Eco-tuning).
Often, the characteristic maps for ignition timing, turbo pressure and air/fuel mixture composition are modified.
Engines with forced induction (turbo / supercharger) are very suitable for chiptuning, both petrol and diesel engines. Naturally aspirated engines (that have to draw in air themselves) are hardly suitable for chiptuning. Power and torque often only increase by a few percent, which is hardly noticeable when driving.
You might wonder why car manufacturers do not simply give a car more power from the factory. Usually the reason is that the settings have been deliberately chosen to meet worldwide emission standards, or because a single car model is available with several engines of the same displacement but with different power outputs. Tuning cleverly takes advantage of this. After tuning, the car of course still has to comply with the legal emission standards.
Chiptuning:
Adjusting the ignition map:
Every petrol engine has a certain ignition advance. With chiptuning, the limit of the ignition advance is pushed a bit further.
For example: With a certain engine with factory software, the ignition advance varies between 30 and 40 degrees before TDC, at an engine speed of 4700 rpm. When the speed is increased to 5000 rpm, the engine will switch to 0 degrees ignition advance.
The tuner will raise the limit at 5000 rpm to, for example, 5200 rpm and only from this speed onward switch to 0 degrees ignition advance. This results in a power gain, because the combustion pressure at this speed becomes higher.
Turbo pressure:
By increasing the maximum turbo pressure, a larger amount of air enters the cylinders. By adjusting the fuel quantity (injection time) accordingly, a strong power gain is achieved. Turbo pressure is controlled by the wastegate. This valve opens at a certain pressure (e.g. 0.8 bar). The tuner will increase this pressure to e.g. 1 bar. The valve will only open when a boost pressure of 1 bar has been reached.
Injection time:
By adjusting the injection time, a larger amount of fuel can be supplied to the incoming air. When the turbo pressure has been increased (more incoming air) and more fuel is injected, a large power gain is achieved.
Not only the characteristic maps for ignition, turbo pressure and injection time need to be modified, but also the maps of all sensors and actuators of the engine.
Take the knock sensor as an example: if its maps are not changed, this knock sensor will respond to the injection time that no longer corresponds to the factory values. This results in a fault code in the ECU (and it may therefore switch to a limp-home program). Every map of every sensor must therefore be programmed according to the modifications that have been made.
Software-based chiptuning:
Nowadays, all chiptuning is loaded into the ECU via software. Through the OBD connector, the software is read from the car’s ECU, modified, and then written back again.
Many tuners offer complete packages for various engine types. This software has been extensively tested and stored.
When the owner of the car has made modifications to the engine himself (think of a larger turbo, larger intercooler, different injectors, etc.), a new tuning program needs to be written. Usually the car is then placed on a dynamometer. The values in the ECU are read out and edited. By then performing new power measurements, the graphs of the power and torque curves can be used to see whether the desired results have been achieved. When the torque or power line shows a strong drop somewhere, this may indicate poor programming. By adjusting the software a number of times and performing a new test run each time, a clean power and torque curve will be obtained (see image).
Replacing the original chip (hardware-based):
The original chip is removed from the ECU and a new chip, pre-programmed with the tuning software, is soldered in. These chips cannot be programmed via the OBD connector. However, this is an older technique and is no longer used on modern cars.
Installing an additional ECU:
With this tuning method, a separate ECU with a wiring harness is supplied. The original ECU is retained and an additional ECU with tuning software is connected. The wiring harness is simply a pass-through system between the two ECUs. Nowadays this technique is increasingly used for tuning, including for Volkswagen. The diagram on the left shows the original ECU and on the right the ECU with tuning software that is connected to the original ECU.
Powerbox:
A powerbox is usually the cheapest, but also the worst way to tune. The powerbox manipulates the input signals to the ECU. This means that the signals sent by the sensors to the ECU are altered. Usually, the signals from the fuel (rail) pressure sensor, the temperature sensors and the mass air flow sensor are modified. The consequences include the fuel pressure / rail pressure rising too high and the air/fuel ratio becoming incorrect because the mass air flow sensor signals have been changed.
Power output will have increased slightly (less than with chiptuning), but the service life of the engine components will be greatly reduced. Internal contamination in the engine will also increase. A powerbox is therefore not recommended.
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