Self Study Program 621 – Audi A3 Sportback g-tron

VAG SSP 621. This Self-Study Programme provides you with information about the CNG system in the Audi A3 Sportback g-tron. The Audi A3 Sportback g-tron showcases state-of-the-art CNG drive technology, starting with the fuel storage. Its two tanks under the luggage compartment floor can each hold 7.2 kg of CNG at a maximum 200 bar pressure referred to 15 °C. In keeping with Audi’s ultra-lightweight construction principle, each tank weighs 27 kg less than its conventional steel counterpart.

The CNG tanks made from an enhanced plastic matrix. A gas-impermeable polyamide polymer forms the inner layer, while a second layer of carbon fiber-reinforced polymer (CFRP) gives the tank its extremely high strength; a third layer of glass fiber reinforced polymer (GFRP) provides protection against exterior damage. High-strength epoxy resin is used to bind the fibrereinforced materials.

The electronic gas pressure regulator reduces the high pressure of the gas flowing from the CNG tanks down to around five to nine bar in two stages. This ensures that the right pressure is always present in the injector rail and at the injector valves. If the pressure in the CNG tanks drops below the required level, the engine management system automatically switches to petrol operation. After refueling, and whenever it is very cold, the engine is started with petrol initially, then it switches over to CNG.

The engine in the Audi A3 Sportback g-tron is based on the 90 kW 1.4 TFSI. Modifications were made to the cylinder head, turbocharging, injection system, and the catalytic converter. Developing 81 kW (110 hp) and 200 Nm of torque, the Audi A3 Sportback g-tron has a top speed of 190 kph, with 0 to 100 kph taking eleven seconds. The five-door model consumes on average less than 3.5 kg per 100 km of CNG. CO2 tailpipe emissions are less than 95 grams per km in gas mode.

Learning objectives of this self study programme:

Once you have completed this Self Study Programme you will be able to answer the following questions:

  • What are the components of the CNG system?
  • How is authorised to carry out work on the CNG system?
  • How do you identify an Audi A3 Sportback g-tron?


  • Introduction
    • Qualification
    • Natural gas
    • Audi e-gas project
    • Vehicle distinguishing features
  • Engine mechanicals
    • 1.4l TFSI engine of the EA211 series (81 kW)
    • Comparison of torque/power curves
  • CNG drive
    • Overview
    • CNG filler neck
    • CNG lines
    • Distributor with non-return valve
    • CNG tank
    • Tank shut-off valves
    • Gas pressure regulator
    • Gas distributor rail
  • Engine management system
    • Sensors and actuators
    • Engine management control unit J623
    • Operating strategy
  • Displays
    • Instrument cluster
  • Service
    • Special tools and workshop equipment
  • Annex
    • Test your knowledge
    • Self Study Programmes
    • Information on QR codes

The Self Study Programme teaches a basic knowledge of the design and mode of operation of new models, new automotive components or new technologies.
It is not a Repair Manual! Figures are given for explanatory purposes only and refer to the data valid at the time of preparation of the SSP. This content is not updated.
For further information on maintenance and repair work, always refer to the current technical literature.

Language: English
Format: PDF
Pages: 40

Self Study Program 621 – Audi A3 Sportback g-tron PDF free online