How do natural gas engines work


Bi or mono

Gas cars are produced in two designs: monovalent or bivalent (sometimes also called monofuel and bifuel), i.e. either with a pure CNG drive or with additional petrol operation. Even if you have your car converted, you can choose any of the variants. Today almost all new vehicles are offered bivalent. The filler opening for petrol is right next to the connection for refueling with gas. In this case, there is no reason to worry about not being able to find a restaurant in remote areas. The car will automatically switch to conventional drive (or you can use the fuel selector switch yourself) and will bring you safely to the nearest gas dispenser. That's where you want to go, because you're always cheaper with natural gas!

graphic: Monovalent (source gibgas)

graphic: Monovalent / gasoline (source: gibgas)

graphic: Bivalent (source gibgas)

Tank well hidden

Your fuel is invisible and lighter than air, but it still needs a little space in the form of fuel bottles. When retrofitting a car, these are usually housed in the trunk. The space available there is then a little smaller, but this has to be offset against the many advantages of the CNG drive. One of the advantages of this technology is that almost every vehicle can theoretically be converted and then protect the environment and your wallet.
In the case of new vehicles, which are designed to run on gas from the outset, the containers are usually installed under the floor. The tanks are located with the petrol tanks under the floor of the vehicle fund instead of in the trunk, thus leaving more space for suitcases and the like.

Drive longer

Today, gas cars can achieve ranges of approx. 400-600 kilometers in CNG operation, depending on the performance and vehicle, monovalent cars with a correspondingly larger tank volume drive a little longer with their pure CNG drive, while bivalent vehicles of course still have a similar one via the gasoline tank additional range. With some models, you can travel more than 1,200 km without refueling - that's roughly the distance from Vienna to Paris.

Dichter saves space

In principle, the same non-toxic gas that we know from cooking, for example, is used for the gas vehicle's engine. To ensure that the vehicle driver has enough energy available in a reasonable proportion to the size of the gas tank, the natural gas is compressed to around 200 bar - hence also: Compressed Natural Gas (CNG).

How does a CNG drive work?

In principle like a gasoline engine, only the compressed gas has to be transported into the cylinders. The operating pressure of 200 bar is reduced to around 5-7 bar (depending on the vehicle type) using a high-pressure regulator or pressure reducer, the gas enters the engine via a low-pressure line and valves, while microprocessors control the gas distributor. There it mixes with air and burns in the cylinder, just like the gasoline-air mixture in conventional vehicles - just as a gas-air mixture. The latest generation of engines usually also has turbochargers or compressors that are optimized for CNG operation and provide even more power. If you then step on the gas properly, this time it really is gas.

graphic: Components of the natural gas installation in CNG vehicles

graphic: VW Golf TGI, technology (© Volkswagen)

graphic: Škoda Octavia Combi G-TEC, technology

graphic: Seat Arona TGI, technology (© Seat)