They are ecological and run on a fuel that is less expensive and just as safe as petrol or diesel; but do we really know how natural gas powered, hybrid cars work? Andrew Shepherd and Antonio Calvo, experts on compressed natural gas cars (CNG cars) at SEAT, tell us all about how these vehicles operate:
You can readily see the two filler necks for both fuel types when you open the fuel door. “Refuelling this hybrid car is the same as on a petrol or diesel car. The filler neck is in the same location and it takes practically the same amount of time. And since the refuelling is done with natural gas, it doesn’t smell or drip”, explains SEAT director of sustainable mobility Antonio Calvo.
They are located beneath the boot floor of CNG cars, where you would normally find the spare tyre, and are made of high resistance steel with an anticorrosion treatment. A set of solenoid safety valves seal the gas inside and only open when the ignition is turned on.
Their condition gets certified every 4 years and the components have been tested to withstand extreme conditions: “The tanks on this car resist 200 bars of pressure, but they’re made to withstand more than double that, so safety is completely guaranteed”, says Antonio.
The tanks are sealed and reach half the pressure they can actually withstand.
CNG cars are equipped with a latest generation internal combustion engine that works indistinctly with compressed natural gas or petrol. By default, the car drives on gas until it is depleted, and automatically switches over to petrol. The driver cannot tell when the shift takes place, as the engine’s performance is exactly the same with both fuel types.
“The engine features many specifically reinforced components for burning natural gas. It complies with the most stringent emissions regulations, and the ECO label issued by the Directorate General of Traffic to cars fuelled with CNG is evidence of this”, explains SEAT CNG product manager Andrew Shepherd.
CNG vehicles comply with the most stringent industry standards. During the entire development stage, they undergo a series of tests, including crash testing, to guarantee they are completely safe.
“In the most extreme case of high temperatures caused by fire, the gas would be released constantly in a controlled manner thanks to the thermal fuses located in each tank, thus preventing an excessive pressure build-up” says Andrew.
For easy refuelling there are two filler necks beneath the fuel door, one for gas and the other for petrol.
The natural gas is housed in the tanks at around 200 bars, but it gets injected in the engine at a pressure that does not exceed 10 bars. A two-stage pressure regulator located in the engine bay reduces the pressure and ensures an optimum gas supply, and the engine control module monitors this electronic regulator at all times.
The feeling at the wheel is the same whether you drive with natural gas or petrol, so the only way the driver can tell the difference is by looking at the indicator on the instrument panel.
When it’s on, the car is operating with natural gas; when it’s off it means the car is in petrol mode. In addition, two further indicators display the level of each fuel type and the trip computer provides information such as consumption and how much range is left.
Andrew Shepherd explains that “gas fuelled cars are designed, made and certified according to the industry’s highest quality standards”. “There are no differences either during their production or when driving them. I like to say that there is absolutely nothing unusual about a CNG powered car, and that it’s just as safe and reliable as all the rest”, concludes Antonio Calvo.