With rising prices for gasoline and diesel fuel, more and more car owners are thinking about converting their vehicles to alternative energy sources. Abbreviation CNG (Compressed Natural Gas) is increasingly appearing in the specifications of new models and in the conversations of mechanics. But what exactly is behind those three letters and why is this type of fuel becoming the standard in commercial transportation and taxis around the world?
Essentially CNG is compressed natural gas, the main component of which is methane. Unlike the usual liquefied petroleum gas (propane-butane), methane is stored in cylinders under high pressure, which allows you to hold a sufficient amount of fuel for a confident mileage. The use of this resource allows not only to significantly reduce refueling costs, but also to reduce the harmful impact on the environment.
In this article, we will analyze in detail the technical features of the system, the nuances of installation and operation, and also answer the question of whether the gamble is worth the candle in the current economic conditions. Understanding of operating principles gas engine fuel will help you make an informed decision about upgrading your car.
Technical features and physics of the process
To understand how CNG differs from other types of fuel, you need to turn to physics. Natural gas extracted from the subsoil consists of 90-98% methane. For use as automobile fuel, it is purified from impurities and compressed by compressors to a pressure of 200-250 atmospheres. Exactly high blood pressure is a key characteristic requiring the use of special cylinders.
Unlike the propane-butane mixture, which at room temperature is in a liquid state under low pressure, methane remains gaseous. This creates certain engineering challenges: cylinders for CNG must be much stronger and heavier to withstand colossal internal stress. Typically steel, metal-composite or all-composite containers are used.
The process of supplying fuel to the engine also has its own characteristics. Gas from the cylinder passes through a reducer, where its pressure is reduced to operating pressure, and then enters the nozzles. Modern control systems such as OMVL or BRC, provide precise dosage comparable to gasoline injection.
Why is methane lighter than air?
Methane (CH4) has a molecular weight of 16 g/mol, while air has a molecular weight of about 29 g/mol. This means that when there is a leak, the gas does not spread along the ground like propane or gasoline, but instantly evaporates upward, which significantly reduces the risk of an explosion in a confined space, such as a garage.
It is important to note that the octane number of methane is 105-110 units, which is higher than that of any gasoline. This allows engines to operate more steadily, without detonation, although it requires proper tuning ignition timing angles.
HBO device for methane: what the system consists of
Converting a car to CNG is a complex technical process that requires the installation of a whole range of equipment. The basis of the system is a block of cylinders, which, due to high pressure, have a cylindrical shape and impressive weight. The placement of containers often becomes the main difficulty when installing on passenger cars.
The key element is the gas reducer-evaporator. Since the gas is greatly cooled with a sharp decrease in pressure, the gearbox is connected to the engine cooling system. Circulating antifreeze heats the gas, preventing freezing of components and ensuring a stable supply of fuel even in cold weather.
☑️ CNG system components
The electronics of modern gas equipment of the 4th generation and higher allows the system to independently adapt to changes in gas composition and environmental conditions. Injectors open and close in milliseconds for precise mixing. Unlike propane systems, the tightness of all connections is critical here due to the small size of the methane molecule.
It is worth mentioning the filter elements. The quality of gas at gas stations can vary, so the presence of high-quality fine filters in front of the reducer and in front of the injectors is a prerequisite for a long life of the system.
Comparison of CNG and LPG: cost-effectiveness
The main question that concerns drivers: which is more profitable? If you compare methane (CNG) and propane-butane (LPG), the difference in price at the gas station can reach a double value in favor of methane. However, savings do not only come from the cost of a liter of fuel.
Gas consumption is always higher than gasoline, by about 15-20%. But thanks to the low price of 1 cubic meter of methane, the final cost of 100 km of track is significantly lower. For commercial vehicles with high mileage payback CNG installation occurs faster, sometimes within 30-40 thousand kilometers.
| Parameter | CNG (Methane) | LPG (Propane-Butane) |
|---|---|---|
| Physical state | Gaseous (compressed) | Liquid (liquefied) |
| Cylinder pressure | 200-250 atm | 10-16 atm |
| Cylinder weight | Heavy | Lightweight |
| Power reserve | Less (due to volume) | More |
However, there is also another side to the coin. There are significantly fewer gas stations with methane than with propane. In large cities and on federal highways the infrastructure is well developed, but in the outback there may be problems. This phenomenon is called range anxiety — fear of being left without fuel.
Effect of methane on engine life
There is a myth that gas “dries out” the engine and causes burnt valves. In reality, everything depends on the quality of tuning and the condition of the motor. Methane burns at higher temperatures than gasoline, but it does so cleaner, without leaving carbon deposits on spark plugs and pistons.
The main problem is the thermal load on the exhaust valves. Since the gas does not wash away the oil film and burns completely, the valves can overheat if the mixture is lean or the cooling system is faulty. Therefore, for engines without hydraulic compensators Valve clearances will require more frequent adjustment.
⚠️ Attention: Installing LPG on an engine with direct gasoline injection (GDI, TFSI, EcoBoost) requires special systems with liquid gas injection or a constant supply of gasoline to cool the injectors. A regular gas reducer will not work here!
The oil in an engine running on CNG retains its properties longer, since unburned fuel and wear products do not enter it. This allows for longer oil change intervals, provided that the specifications recommended for the oil are used. gas fuel.
Safety of operation and storage
Safety is the main trump card of methane. As already mentioned, it is lighter than air. In the event of an accident or damage to the pipeline, the gas will simply escape into the atmosphere without forming an explosive cloud near the ground, as propane or gasoline vapor does.
CNG cylinders undergo the most stringent tests. They are made with a multiple safety margin. They are able to withstand gunshot wounds (the bullet simply penetrates the wall without causing a rupture) and falls from great heights. It must be installed on the neck of the cylinder fire valve, which shuts off the gas supply when the temperature rises critically.
When purchasing a used car with LPG, be sure to check the inspection date of the cylinders. For composite tanks, the service life is limited, and an expired cylinder is a direct threat to life and problems during technical inspection.
However, regular diagnostics of the tightness system using a gas analyzer is mandatory. Methane is odorless, and it is more difficult to sense its leak by its characteristic “aroma” (odorant) than propane, since the concentration of odorant in methane is lower.
Prospects and environmental aspect
In conditions of tightening environmental standards (Euro-5, Euro-6), methane becomes an ideal transition fuel. During its combustion, virtually no particulate soot particles are formed, and emissions of nitrogen and carbon oxides are minimal. This makes CNG attractive to environmentally friendly zones in the centers of megacities.
Many automakers, including Volkswagen, Mercedes-Benz and Volvo, produce factory models that run on methane. Such cars have a guarantee and gas-optimized operation of all systems, which eliminates many of the problems that arise with a makeshift installation.
The future belongs to bio-methane, which is produced from agricultural waste. It is a completely renewable resource that makes transportation virtually carbon neutral. Gas station infrastructure continues to grow, supported by government programs in many countries.
Switching to CNG is a strategic decision for those who drive a lot. The high initial cost of the equipment is compensated by the low price of fuel and increased engine life with proper maintenance.
Is it necessary to register the installation of gas equipment with the traffic police?
Yes, the installation of gas equipment is a change in the design of the vehicle. According to the technical regulations, it is necessary to undergo a preliminary examination, install certified equipment, obtain a safety inspection protocol and make changes to the STS and PTS. Driving with an unregistered gas equipment may result in a fine and a ban on operation.
Will engine power decrease on methane?
Theoretically, methane has a slightly lower energy content than gasoline, which could result in a loss of 5-10% of power. However, in practice, with proper calibration of the ignition and the use of high-quality 4th generation systems, the driver practically does not notice the difference in acceleration dynamics.
Is it possible to refuel with methane in winter?
Yes, you can. Since methane is stored in a gaseous state, it does not have the evaporation problems that propane has in extreme cold. The pressure in the cylinder depends on the temperature, but remains sufficient for engine operation even at -30°C and below.