Frequently Asked Questions about CNG

CNG is the abbreviation for Compressed Natural Gas. It is a natural product, which covers basically all aerially hydrocarbon compounds that originate from the earth, and which can be combusted. Natural gas consists by volume of at least 85% methane as well as up to 10% of nitrogen and carbon dioxide. The rest is made up of gases like ethane, propane and butane. It belongs to the same group of organic resources like crude oil and coal.

In principal, natural gas can be offered in two forms:

CNG (Compressed Natural Gas, stored at a pressure between 200 -240 bar)

LNG (Liquid Natural Gas, stored at -164°C; this way, the volume can be reduced to 1/6000 of its original size)

Currently, only Compressed Natural Gas (CNG) is offered in Singapore.

CNG is basically composed of methane whereas LPG is a mixture of propane, butane and other chemicals.
Another important difference from a physical point of view is that CNG does not liquefy under high pressure - it remains a gas, unless it is cooled down to at least - 164°C. LPG on the other hand becomes liquid when it is compressed or when it is cooled down (therefore the name "Liquefied Petroleum Gas").

CNG directly comes from a gas field. The only process, which sometimes needs to be done, is filtering the gas. But usually, the gas can be used as a fuel right away after the compression process. LPG, however, is an artificial product. It is a mixture of the above-mentioned gases. Hence, these gases need to be blended, before they can be used as fuel.

CNG has a greater part of Hydrogen and is therefore lighter than air (this attribute in fact makes CNG very safe: once there is a leak in the system, the gas will simply be released to the atmosphere). LPG on the other hand, is twice as heavy as air. This gas is usually a by-product which accumulates from the oil drilling as well as the refinement of oil.

Prices of conventional fuels such as Petrol and Diesel are quite high, and it is foreseeable that these will rise even further. The prices for CNG, however, are much lower than that of Petrol and Diesel. Gas is therefore a cheap alternative fuel.

Further, the gas for Singapore is supplied by gas fields, which are located in nearby countries such as Malaysia and Indonesia. The transportation of gas is therefore quick and short. Thus, a continuous supply is guaranteed, and due to the vast resources, the prices for CNG in Singapore will stay low for a long time.

Yes, it is. As CNG mainly consists of methane, the exhaust fumes of CNG basically consist of water vapours, Carbon Dioxide and some fractions of Carbon Monoxide. There are no other carbons or toxic particles in the exhaust fumes. It is therefore much environmentally friendlier than other fuels. Thanks to that, CNG vehicles fulfill all present emission standards worldwide (such as the European EURO 4 standard). They do not need any additional aids, such as catalytic converters, etc.

No, CNG is neither poisonous, nor does it contain toxic substances or other cancer-causing contents.

CNG in its pure form does not smell. However, for safety reasons, scents are mixed with the CNG. This makes it possible to notice whether there is a leak in the system. These strong-smelling scents are not hazardous. They can be smelt at a low concentration of CNG. That means, once the "Gas" can be smelled, the concentration is still too low to ignite. The scent is the same as your household gas. If this smell can be perceived, a certified car workshop should be visited, and the car should be checked for possible leaks.

Generally speaking, a CNG gas tank is much more secure than a conventional Petrol tank. Petrol tanks are usually made of plastic, which is much less secure than a robust gas cylinder of pure steel. And even though the Petrol tank is made of plastic, only very few cars burn after an accident.

Further, once the pressure of the line from the gas cylinder to the engine exceeds a certain pressure, the valve at the cylinder will automatically shut. This way, maximum security is guaranteed, and no gas is able to evaporate. Even police cars drive on CNG in certain countries.

The resources of crude oil are estimated to be exploit within this century. However, the natural gas fields are said to supply sufficient gas until the next century. Gas supply will therefore certainly last longer than the life expectancy of your current CNG car.

In order to enjoy the vast benefits of CNG, one can purchase a brand new Natural Gas Vehicle. A much more simple way to get a CNG powered vehicle, however, is to simply convert the petrol car into a bi-fuel vehicle.

Taking all these positive effects into consideration, potential buyers also have to keep in mind that there are some disadvantages of a CNG modification.

Usually, the cylinder(s) are installed in the boot of the car, which means, that the storage capacity in the boot is reduced. For an idea of the decrease in storage capacity, images of installed cylinders can be seen on our carconversion gallery page. You may also drop by our workshop and try test-fitting a mock cylinder into your boot.

One other issue with running on CNG is mileage of your vehicle, which is limited by the capacity of the cylinder and the CNG infrastructure network in Singapore.

The standard installed cylinder may hold up to 11kg of natural gas at 220 bar with a fuel consumption of about 8kg/100km (2.4L engine), giving you a mileage of about 150km. The mass (kg) of gas that is filled into a tank upon refueling is dependent on the configuration of the gas station where you refuel at, and not something that is determined by the kit that we install. CNG Stations operate compressors and depending on the efficiency of that compressor you may or may not get a 100% full tank.

CNG conversion is a modification to your car, turning your car into a bi-fuel car. On petrol, your car will run as usual, but whilst running on CNG you may suffer a loss in performance. This is due to the fact that CNG and petrol are different forms of fuel. It can affect drivers who drive too gently, and also drivers who drive aggressively. Because of this, you may need to adapt your driving style to suit the optimal running of CNG.

Here are some recommended links:

• Land Transport Authority Singapore
• National Environment Agency
• International Associations for Natural Gas Vehicles
• NGV Global Home
• Clean Vehicle Education Foundation
• Green Car Congress
• Cleanest Internal-Combustion Vehicle on Earth
• How Natural-gas Vehicles Work