Modern turbocharged engines are controlled by an ECU (Electronic Control Unit). By placing custom software in the ECU in which the amount of fuel injection and turbo pressure is adapted, a 25-30% increase in power is possible, for petrol and diesel engines. This is called remapping, or chip tuning.
The original software is read from, edited and restored on the memory of the ECU. Because of the increased power (with the same driving style) a fuel consumption reduction of 5 to 10% is possible thanks to the higher efficiency. The resulting higher power can also be used to increase speed. As a result, however, the fuel-saving effect is then lost.
Chiptuning BMW M5 with dynamometer
Chip tuners often use a rolling road to measure the output before and after tuning. In the video below we see a BMW M5 which has been tuned by a French tuner. The power has increased from 545 hp to 673 hp and torque from 720 Nm to 857 Nm, with the aid of an Akrapovic exhaust.
OBD tuning
Reading and reinserting the custom software in the ECU is often done by “flashing” the chip via the OBD interface (On Board Diagnostics). The advantage of tuning through the OBD interface is that nothing has to be disassembled and the tuning is done via a special OBD connector, which is usually located somewhere in the dashboard of the car. You can make your car original very simply this way too. Some tuners even provide a device with which you can load the software yourself.
BDM tuning of an ECU
With modern ECU’s a tune through the OBD port often is not possible because of security measures. In that case, the tuner might have to take the ECU out of the car and connect it directly to a computer via the BDM interface (Background Debugging Mode) located on the ECU itself. In some cases, a special socket has to be soldered in order to read out the software. After the editing, the software is written back to the ECU through this port again.
Example BDM tuning of an ECU
Powerbox
In addition to optimizing the ECU software itself there is also the possibility of “fooling” the ECU with a so-called “Powerbox”. This power box is placed between the transmitters and the ECU, providing other data to the engine control than the channels themselves. The engine management system responds by eg. increasing the amount of fuel or turbo boost, and this way you will get more power. The results of a Powerbox are varying, and this method is generally not recommended.
External ECU
As mentioned, many modern ECU’s are protected from external access by the manufacturer. If the ECU is really inaccessible, sometimes an external ECU (ECM or External Control Module) is used. This external box is coupled to the engine and has its own software. The external ECU can adapt much more than one or two values, and while tuning the software on the ECU itself (remap) still is considered the best way of tuning, this method is in contrast to the above power box solution, a reliable way to tune. The fact that the car remains original is an advantage too. You can easily remove the tuning this way by disconnecting the unit.
Tuning of naturally aspirated engines
On engines without a turbo remapping gains are usually relatively small (a few percent) and therefore tuning of those engines is not often performed.
Manufacturers do it themselves
For marketing reasons a car model sometimes comes with the same engine with different power output. The Volvo 2.4D five-cylinder diesel engine is an example. It delivers 163hp and 340nm of torque. The engine is identical to the D5 which delivers 185hp and 400Nm. The 2.4D is down-tuned to a lower power output and, therefore, very easy to tune to its “original” power or more. The Volkswagen 1.0 TSI is another example, with power outputs ranging from 85 to 115 hp. Sometimes power trains differ in parts (eg. turbo, clutch, gearbox) and then the engine needs to be tuned accordingly.
Cons of ECU remapping
There are many car owners who have had their car tuned and have had years of troublefree driving. However, there are also negative aspects to chip tuning that are not always mentioned by chip tuning companies. You better weigh up the advantages against the disadvantages in order to make an informed choice for chip tuning.
Fuel consumption not always lower
At constant driving your fuel consumption can be slightly lower after a remap. The extra power will however also be used for more speed, simply because it’s fun. You can feel in your bones that a tuned engine uses more fuel in that case; after all, more fuel is injected for the bigger bang that is required. Consumption therefore fully depends on your driving style.
Engine margin
With more torque gives you margin used by the manufacturer to ensure that the engine performs adequately in all (extreme) conditions and has a long life. The manufacturer must take into account poor quality fuel, extreme temperatures, poor maintenance and especially the abuse / use of the driver (no warm up, and much or little load (long-term full load, caravanning etc.). Combine this with tuning and you can expect problems.
Tolerance power train
A more powerful engine will put more strain on the rest of the power train. The parts can therefore wear more quickly. In addition, these components also have certain tolerances, i.e.. The amount of torque that the clutch or gearbox can handle. If the tolerance is exceeded, or parts are already worn, problems may manifest themselves quickly after remapping. A good chip tuner will advise you when to expect certain problems after tuning, and take into account the specifics of your car.
Warranty
If you do not use a tuning approved by the manufacturer or approved dealer to tune the car, you usually lose (factory) warranty. You can therefore enter a discussion in case of problems with the powertrain, including a very fast worn clutch, clogged DPF, gearbox problems or blown turbo. Leasing companies are not keen on tuning and it is therefore often not allowed, even if the tuning is done by an approved dealer.
Software updates
Manufacturers provide regular software updates for the engine of their cars. For older cars this isn’t much of a problem, but modern cars regularly receive an update when in the garage for maintenance. Although there are several types of updates, it can happen that the tuning is overwritten. In that case, you’l have to return to the tuner for a re-tune. This is often done free of charge, but if it’s a lot of work (bdm tuning for example) the tuner sometimes asks a fee for it.