At Volkswagen, TDI refers to diesel vehicles with direct injection and turbo charging. TDI engines are characterised by high levels of tractive power (torque) and and very good performance yield. TDI is a registered trademark of Volkswagen AG in many countries.

How it works:
a turbocharger supplies the engine with fresh air, ensuring optimum filling of the cylinder. After compression, the diesel fuel is then directly injected into this using a nozzle at a very high pressure. Effective engine encapsulation also enables quiet operation.

See also:
Direct injection

Image of the TDI label on Volkswagen diesel vehicles

Test cycle 

The legislator prescribes standardised test procedures for the type testing of new vehicles. The procedures measure exhaust emissions, consumption and CO2 emissions, as well as the range with electric vehicles. In the past, this was done in the EU on the basis of the New European Driving Cycle (NEDC). The latter was superseded in September 2018 by the WLTP (Worldwide Harmonized Light Vehicles Test Procedure). The WLTP is intended to provide customers with more realistic current consumption values and ranges. The new test cycle is considerably longer and the test procedure is significantly more complex than the previous one.


TGI refers to the combination of a standard natural gas drive with innovative TSI technology used to directly inject petrol into turbo-charged petrol engines.
The bi- and quasi-monovalent TGI engines run on natural gas and petrol. To exhaust the full potential of natural gas as a fuel, various measures are taken to modify the engines and adapt them to suit running on natural gas.

3. Fuel consumption Polo GTI natural gas (CNG), kg/100 km: urban 4.4-4.1 / extra-urban 2.9-2.7 / combined 3.4-3.2; CO₂ emissions combined (natural gas (CNG)), g/km: 93-88; efficiency class: A+

Schematic diagram in the VW Polo with TGI natural gas mode

Tilting and sliding panoramic sunroof 

The tilting and sliding panoramic sunroof is an enhancement of the panoramic sliding roof. The roof opening system consists of at least two glass elements.

The front glass section has an electric lift and slide function. It can be tilted or opened fully. When the sunroof is slid open, the front element covers the rear element completely. The rear glass element is fixed and does not open.

The tilting and sliding panoramic sunroof has an electric roller shade that covers the entire roof.

Image of vehicle roof with tilting and sliding panoramic sunroof in the VW Passat


Torque is the force applied to a centre of rotation under a lever arm (torque = force x lever arm). The physical unit of torque is the newton metre (Nm). Modern engines should provide the highest possible torque at the lower end of the engine speed scale and the ‘widest’ possible engine speed range. An example of this is the progression of the torque of the 1.4 litre Twincharger engine: a high torque at low engine speeds (250 Nm at 1,500 1/min) and constant up to the high engine speed ranges (up to 4,500 1/min). This indicates powerful traction when starting and overtaking and lots of driving fun.

Torsen differential 

The Torsen differential is a component of the 4MOTION all-wheel drive. It is a mechanically self-locking centre differential that controls the force between the front and the rear axle depending on requirements.

See also:

Schematic diagram of Torsen differential as component of the 4MOTION all-wheel drive in the VW Touareg

Torsion beam rear axle 

The torsion beam rear axle is the most economically efficient non-driven rear axle design. Two trailing arms are connected by a transverse beam that also acts as a stabiliser. The advantages of this design are the good lateral guidance on corners and a compact spatial requirement that enables economical use of space in the rear.

See also:
MacPherson axle
MacPherson suspension strut
Double wishbone axle
Semi-trailing arm axle
Multi-link rear axle
Four-link front axle
Trapezium link rear axle

Towbar, swivelling  

The swivelling towbar can be swivelled out electrically or manually, depending on the vehicle. It is released using a switch or handle in the vehicle interior. Once released, the towbar must always be swivelled back in manually. When folded in, the towbar disappears entirely beneath the vehicle.

VW Golf, towbar detail

Traction Control System (TCS)  

For high-torque engines, the Traction Control System offers more comfort and safety, particularly on roads with differing degrees of gripping and slipping. The Traction Control System enables harmonious starting and acceleration processes across the entire speed scale without spinning wheels or lateral offset.
The Traction Control System works with the electronic accelerator pedal (EPC) and uses the wheel speed sensors of the anti-lock brake system (ABS). If a sudden increase in speed (slippage) is detected on a drive wheel, the system intervenes in engine management, reduces the engine performance and prevents this effect.
The Traction Control System guarantees traction and driving stability during the acceleration phase across the entire speed range, thus supporting active safety. It also reduces wear on tyres. The Traction Control System includes the electronic differential lock and is part of Electronic Stability Control.

See also:
Electronic accelerator pedal (EPC)
Anti-lock brake system (ABS)
Active safety
Electronic differential lock (XDL)
Electronic Stability Control

Traction Control System (TCS) warning lamp in a VW Golf

Traffic Jam Assist 

Traffic Jam Assist uses reliable functions such as Adaptive Cruise Control ACC and the Lane Assist lane keeping system to ensure convenient distance control in traffic jams. In slow-moving traffic from 0 - 60 km/h, the system reacts to other vehicles and takes over steering, acceleration and braking, within the system's limitations, under the driver’s constant supervision. If traffic stagnates, it even stops the vehicle and starts it again within a certain period of time. Unlike pure Adaptive Cruise Control (ACC), Traffic Jam Assist uses a camera behind the windscreen that looks out for road markings. This keeps the vehicle in lane. Traffic Jam Assist makes life easier in stop/start traffic, helping to avoid typical traffic accidents.

Three vehicles seen from above, stuck in traffic on a street. The Traffic Jam Assist sensor system is depicted using lines

Traffic message channel (TMC) 

TMC (traffic message channel) supplies data on the current traffic situation. The navigation system uses this to calculate an adjusted traffic route (dynamic route guidance). Information is transmitted consistently throughout Germany. TMC is now also available in large swathes of Europe. Data is transferred digitally and irrespective of language as part of the RDS. The data is displayed in the user’s set language of their country.

See also:
Radio Data System (RDS)
Route guidance, dynamic

Image of the Traffic Message Channel (TMC) multimedia system in the VW Touareg

Traffic sign recognition 

Traffic sign recognition informs the driver of the current traffic situation. The system uses a camera to record traffic signs on the roads. They are displayed on the multifunction display and/or the navigation system display.
The driver can focus on what's happening on the road and their life is made easier in complex situations. Traffic sign recognition processes three different pieces of information for an optimum display: ‘Traffic signs detected’, ‘Navigation system information’ and ‘Current vehicle data’.

See also:
Driver assist systems

Image of traffic sign recognition in the multifunction display of the VW Golf

‘Trailer Assist’ trailer manoeuvring system

For the uninitiated, manoeuvring with a trailer can truly test the patience. The trailer does not always react the way you might expect: and what's more, the route travelled appears in mirror image. The steering angle is important for exact reversing. The ‘Trailer Assist’ trailer manoeuvring system takes charge of steering. All the driver needs to do is simply go into reverse, touch the park button and choose the preferred direction of travel for the trailer using the mirror adjustment switch. The vehicle is now steered automatically. But the driver is still in charge of using the switch, accelerating and braking.

Schematic diagram of the ‘Trailer Assist’ trailer manoeuvring system in a VW Touran

Trailer stabilisation  

Electronic trailer stabilisation is a subfunction of Electronic Stability Control. The system detects vehicle instability caused by travelling with a trailer without adjusting speed. The trailer is steadied by specifically reducing the engine torque and appropriate braking of individual wheels. Trailer stabilisation therefore makes a major contribution to increasing trailer safety.

A VW Golf, viewed from above, reverses around a corner with a trailer


TSI refers to direct injecting, turbocharged petrol engines from Volkswagen. The innovative TSI engines combine the positive characteristics of direct injection diesel and petrol engines to meet the highest standards and offer maximum driving fun. All TSI engines offer remarkably low consumption, high pulling power and high torque even at low engine speeds.

Image of the TSI petrol engine of a VW Golf


By compressing the air required for combustion, turbochargers boost an engine’s air flow. This means that in comparison to suction engines (with identical capacity), the use of turbochargers can not only increase performance and torque, but efficiency, too.
The turbocharger consists of two statically connected turbines. One is driven through the hot exhaust gas stream. The other turbine, known as the compressor wheel, is also turned by the static connection and compresses the fresh air flowing in. The temperature of the compressed air is cooled by a charge air cooler to reduce the volume and increase the amount of air, or oxygen, in the combustion chamber. The use of the turbocharger not only boosts performance but also primarily saves on energy and reduces emissions.

See also:
Variable turbine geometry

Turbocharger in front of a white background

Turning further angle sensor

The navigation system’s turning further angle sensor records changes in vehicle direction to the right or left. In combination with information from the wheel speed sensors on the distance covered, the navigation control system calculates the course of the journey and the curve radius. This data is important for what is known as dead reckoning navigation. Dead reckoning navigation increases the accuracy of positioning and permits route calculation in the event that GPS signals cannot be received at some point, such as when going through a tunnel.

See also:
Navigation system
Wheel speed sensor

Interior view of a Volkswagen, on-board computer with navigation detail

Tyre Mobility System 

The breakdown set (Tyre Mobility System) is used to reseal small punctures (up to 4 mm in diameter), particularly in the tread, and pump the repaired tyres back up.

It contains the following components:

  • Valve core remover
  • Sticker with speed indication ‘max. 80 km/h’ or ‘max. 50 mph’
  • Tyre sealant tube with sealing plug
  • Compressor
  • Tyre filler hose
  • Tyre pressure gauge
  • Air extraction screw
  • ON and OFF switch
  • 12-volt connector
  • Tyre sealant can with sealant
  • Valve core replacement
Image of the ‘Tyre Mobility System’ breakdown set

Tyre Pressure Loss Indicator 

The Tyre Pressure Loss Indicator runs using the ABS wheel speed sensors. If tyre pressure is decreasing, the relevant wheel’s rolling radius is reduced and it turns faster at the same vehicle speed.

The Tyre Pressure Loss Indicator helps the driver monitor tyre pressure. Permanent monitoring ensures a high level of safety. The right tyre pressure helps lengthen the lifespan of tyres and reduce fuel consumption.

However, the Tyre Pressure Loss Indicator cannot release the driver from their responsibility to monitor tyre pressure.

See also:
Wheel speed sensor
Tyre Pressure Monitoring System

Image of Tyre Pressure Loss Indicator lamp

Tyre Pressure Monitoring System  

The Tyre Pressure Monitoring System informs the driver of the current tyre pressure before and during the journey. Sensors are built into every wheel (including the spare wheel) alongside the wheel electronics unit. The wheel sends wireless signals to a control unit in the rear of the vehicle. These provide information on the tyre pressure and temperature. Each electronics unit transmits its own identifier to allow individual tyres to be pinpointed. If tyre pressure is too low or pressure is lost quickly, visual and/or audio signals warn the driver.

The monitoring system helps the driver monitor tyre pressure. Permanent monitoring ensures a high level of safety. The right tyre pressure helps lengthen the lifespan of tyres and reduce fuel consumption.

However, the Tyre Pressure Monitoring System cannot release the driver from their responsibility to monitor tyre pressure.

See also:
Tyre Pressure Loss Indicator

Image of the Tyre Pressure Monitoring System in the VW Passat’s multifunction display