This is the Audi A3 Sportback g-tron that will make its debut at the end of the year. ‘G’ stands for gas, and this A3 is powered by compressed natural gas (CNG). But Audi isn’t just rolling out the car, they’re making their own gas as well!
With Audi e-gas, Audi says that it’s the first carmaker to develop an entire chain of sustainable energy carriers. The start of the chain has electricity produced from renewable energy sources; the end products are hydrogen and the synthetic e-gas. Construction of the world’s first industrial plant to produce synthetic methane from CO2 and renewable electricity is almost complete in Werlte, Germany.
The Audi e-gas plant uses renewable electricity in the first stage for electrolysis – splitting water into oxygen and hydrogen, which could one day power fuel-cell vehicles. Because there is not yet a widespread hydrogen infrastructure, however, the hydrogen is then reacted with CO2 in a methanation plant to produce renewable synthetic methane = Audi e-gas.
Chemically speaking, Audi’s e-gas is identical to fossil-based natural gas. As such, it can be distributed to CNG stations via the standard natural-gas network.
As for the car, it showcases new CNG drive technology, starting with the fuel storage. Its two tanks under the luggage compartment floor can each hold seven kg of CNG at maximum 200 bar pressure.
The inner layer of the tank consists of gas-impermeable polyamide polymer, while a second layer of carbon fiber-reinforced polymer (CFRP) gives the tank strength; a third layer of glass fiber reinforced polymer (GFRP) provides rugged protection against damage from the outside. High-strength epoxy resin is used to bind the fiber reinforced materials. Audi says that each tank weighs 27 kg less than a conventional unit.
A second highlight is the electronic gas pressure regulator. This compact and lightweight component reduces the high pressure of the gas flowing from the cylinders down to around five to nine bar in two stages. It ensures the right pressure in the gas rail and at the injector valves – low pressure for efficient driving in the lower speed range, and higher when the driver needs more go.
If the pressure in the tank drops below ten bar, the car automatically switches over to gasoline operation. The g-tron is fully bivalent, which means that its performance figures are identical in CNG and gasoline modes.
The engine is a 1.4 TFSI with key mods to the cylinder head, turbo, injection system and catalytic converter. Developing 110 hp and 200 Nm of torque, the A3 Sportback g-tron has a top speed of 190 km/h and 0-100 km/h time of 11 seconds. Average CNG consumption is less than 3.5 kg per 100 km, while CO2 emissions are less than 95g per km in gas mode.
CNG provides a range of around 400 km, while the petrol adds on another 900 km if necessary. This equates to a total range that is approximately on a par with a TDI-powered conterpart.