Gearbox reprogramming

Contrary to what you might think, reprogramming is not limited to the ECU. In fact, most vehicles are equipped with a multitude of ECUs (sometimes over 50!), each of which has a well-defined role. There are ECUs for almost every aspect of the vehicle, including air conditioning, suspension and the gearbox. In theory, they can all be reprogrammed. In this article, we’ll focus on the gearbox, because its reprogramming represents real added value in terms of driving pleasure and performance.

Gearbox types

Before delving into the heart of the matter, you need to know that there are different types of gearboxes that can be reprogrammed. In theory, it’s possible to reprogramme any ECU, but in some cases (e.g. CVTs), there is no real point in doing so because the vehicles are not sporty and there would be no significant benefit. The two best gearbox types for reprogramming are dual-clutch gearboxes and torque converter gearboxes.

The dual-clutch gearbox is an advanced technology that combines the efficiency and responsiveness of a manual gearbox. It features two separate clutches, one for odd gears and one for even gears. When changing gears, the gearbox pre-selects the next gear, enabling near-instantaneous changes without any interruption in power. This system offers faster acceleration and better fuel economy than traditional automatic gearboxes. Dual-clutch gearboxes are particularly popular in sports cars, although their programming can sometimes make driving a little rough if not performed properly. Examples of dual-clutch gearboxes include DSG (VW Group), PDK (Porsche), DCT (Alpine), and more.

The torque converter gearbox is a classic type of automatic transmission. It uses a hydraulic torque converter to link the engine to the transmission, replacing the traditional manual gearbox clutch. This converter enables smooth gear changes and absorbs engine shocks, providing a smooth and comfortable driving experience. Although generally less responsive than dual-clutch transmissions, torque converter transmissions are robust, reliable and suitable for everyday driving as well as for heavy vehicles. Moreover, they are renowned for their ability to handle high levels of torque. Originally, these transmissions were not intended to be reprogrammed, based on their technology and relatively slow gearshifts compared with dual-clutch transmissions. However, advances such as those in the ZF’s 8-speed gearbox (ZF8) have expanded the options available, and today, torque converter gearboxes are installed in a wide range of vehicles, including sports cars, sedans or SUVs (e.g. the RS6 C8, the recent M3 G80, Range Rovers, Alfa Romeo Stelvio, etc.).

Which parameters are changed during reprogramming?

Significant changes are made to the gearbox to improve both performance and the driving experience. The main benefits are:

Reducing gearshift time: By reducing the time needed to change gears, the vehicle becomes more responsive. However, the margin for improvement depends on the gearbox itself and its tolerance levels. For example, the Volkswagen Group’ DSG gearboxes offer significant potential for improvement, while other gearboxes (e.g. those in Ferraris) are already very fast, with a shift time of around 60 ms, which can only be optimised very slightly.

Customising driving modes: By adjusting the driving modes, the gearbox responsiveness can be modified to meet the driver’s preferences, e.g. for more economical driving or for sporty driving. For fans of manual gearboxes, it’s even possible to lock the gears in manual mode.

Modifying torque limiters: All gearboxes are fitted with one or more torque limiters. When the engine ECU requests a certain level of torque, this value is transmitted to all the vehicle’s ECUs. If the engine ECU requests a torque of 500 Nm and the gearbox has a torque limiter at 450 Nm, the gearbox will limit the torque. By adjusting the gearbox torque, the total torque of the vehicle can be increased. Consequently, both its performance and driving pleasure will be improved.

Increasing the rev limit: Each gearbox has a rev limit. For example, if the ECU requests a speed of 7000 rpm but the gearbox has a limit set at 6500 rpm, this may restrict the vehicle’s maximum power. By adjusting the rev limit, the vehicle’s power can be increased, and when shifting gears, a rev range with greater power can be favoured over another. This optimises the vehicle’s overall performance.

Increasing the pressure on the plates: On dual-clutch gearboxes, the pressure on the plates can be increased. On a DSG gearbox, for example, the pressure can be increased from 15 to 16 bar, considerably boosting the maximum torque allowed by the gearbox. This modification is generally accompanied by a physical change to the clutch plates.

The impact of modifications on driving pleasure

Some changes do not directly affect the vehicle’s power, but they have a significant impact on what is known as “drivability”, i.e., the level of driving pleasure under normal circumstances. Manufacturers often relegate this to second place, because the average driver is not particularly sensitive to it. This is why it is common for gearbox calibration to be outsourced to external companies who have limited time and budgets to do the job. As a result, some gearbox calibrations are not fully optimised, which can sometimes result in inaccurate or inappropriate gearshifts. The process of readjusting these elements is both complex and demanding, but it can make a huge difference and it’s just as important for the user’s driving experience as reprogramming the engine itself.

At WOT, we attach great importance to a pleasurable driving experience. To benefit from consistent reprogramming, it’s crucial to work on the gearbox. When we have access to the gearbox TCU, we systematically reprogram it with the aim of creating a vehicle that provides consistent increased performance and optimum driving pleasure.