Audi unveiled a CNG-powered A5 coupe last year called the Audi A5 2.0 T-CNG, powered by a 2.0 litre TFSI CNG engine which can run on both normal petrol and Compressed Natural Gas, which is what our NGV vehicles in Malaysia run on.
The Audi A5 2.0 TFSI CNG is designed to provide similiar power and torque outputs as the base A5 1.8 TFSI model. It can produce 170 PS, similiar to the 1.8 TFSI model’s 170 PS figure. This 2.0 litre engine can produce the same power figures running on both petrol and natural gas. It is said to be an enlarged version of the 1.8 TFSI engine rather than using the 2.0 TFSI in the Golf GTI.
CNG is stored in four pressure tanks with a total volume of 130 litres, which according to Audi is able to store 21kg of CNG. This allows a total mileage of 420km from the CNG alone. The conventional petrol tank has been reduced to a mere 14 litres, which Audi says is good for 180km.
The engine’s ECU is modified to support CNG operation, with new features and functions to support controlling the CNG injectors as well as facilitating a smooth changeover between CNG and petrol. The coating of the catalytic converter is modified to take into account the different exhaust gas composition.
The direct injection feature of the engine allows the air-CNG mixture to be compressed up to a high 12:1 compression ratio, which allows the engine to extract much more power out of similiar amounts of CNG compared to what non-direct injection CNG engines can do, which have to run at lower compression to prevent engine knocking when petrol is being used as fuel. This is because CNG is naturally knock-resistant.