Q: What is CNG?

CNG stands for Compressed Natural Gas. A gaseous fuel, CNG is a mixture of hydrocarbons, mainly methane, in the range of 89% to 90%. Due to its low density, it is compressed to a pressure of 200-250 Kg/cm² (g) to enhance the vehicle’s on-board storage capacity.

Q: Is CNG safe?

The properties of CNG make it a safe fuel. It is lighter than air, so in case of a leak it rises and disperses into the atmosphere.

Q: How to convert a vehicle to a CNG-friendly vehicle?

A: All spark-ignited engines can be converted to CNG. There are specially designed conversion kits available to help you convert your vehicle to CNG. The kit consists of a cylinder that has to be fixed in the boot of the car and other equipment to allow gas flow into the engine.

Q: Can a CNG-fitted car run on petrol after its runs out of CNG?

A: CNG vehicles have dual fuel facility. Even after conversion to CNG, the vehicle continues to be fitted with the petrol carburettor and fuel tank. You can switch to petrol by simply by flicking a switch on the dashboard.

Q: What is the cost of converting a vehicle to a CNG-friendly one?

A: Depending on the make and type of the kit converting to CNG can cost anywhere between INR 25,000 to INR 55,000 (approximately).

Q: What are the dimensions and weight of a CNG cylinder?

A: CNG cylinders are compact in size and can easily fit in a small car. An empty CNG cylinder with a 50 litre water-carrying capacity weighs 48 kg (approximately), and has a length of 835 mm and a diameter of 316 mm. The 50 litre capacity cylinder is one of the most regularly used cylinders, but cylinders with 45 litre, 55 litre, 60 litre and 65 litre capacity are used as well.

Q: What is the capacity of a cylinder, and mileage from one fill? How does one get to know the quantity of CNG left in the cylinder?

A: A cylinder with a 50 litre water-carrying capacity is capable of carrying approximately 9 kg of CNG. This is equivalent to 12.5 litres of petrol and will allow a run of about 150-160 kms on a medium sized 1300 CC car. An electronic fuel gauge fitted on the dashboard as part of the conversion kit indicates the quantity of CNG left in the cylinder.

Q: What is the pressure of CNG in a cylinder? Is refuelling of a cylinder safe, given the pressure?

A: CNG cylinders are designed and built to withstand high pressure. The maximum pressure in a CNG cylinder is up to 200 kg/cm2 (g) (about 2840 pounds per square inch (gauge) or psi[g]). CNG cylinders are safe as they are manufactured as per specific requirements and tested before use, in accordance with international specifications and standards, and are duly approved by the Chief Controller of PESO. Moreover, they are provided with a pressure relief device (PRD) that consists of a fusible plug and a burst disc that ruptures in case of inadvertent high pressure and temperature.

Q: How much will I save by converting my vehicle to CNG?

A: You can expect to reduce your fuel bill by 60 percent approximately. The cost of installation of the kit can be recovered within a year,

Q: Does CNG kit require servicing?

A: CNG kit doesn’t require frequent servicing, but just routine services by an authorised person. As per Gas Cylinder Rules, 1981, the cylinder should undergo hydro-stretch testing every 3 years to check pressure tolerance.

Q: Does CNG have any harmful effect on the engine?

A: CNG’s distinct features do not contaminate or dilute crankcase oil, giving engine. The absence of any lead content in CNG avoids lead fouling of plugs, thereby enhancing plug life. One of the important benefits of CNG is that upon entering the engine in the form of a gas (and not as a spray or mist like other fuels), it doesn’t disturb the presence of lubricating oil in the engine, and reduces chances of wear and tear.

Q: How does the performance of a CNG-converted vehicle compare with that of a petrol-run vehicle?

A: CNG provides easy starting, reliable idling and smooth acceleration. The acceleration of a CNG vehicle is a bit slower, which is due to a power loss of 5-15%. This can be minimised by proper tuning on CNG like advancing the spark timing to take advantage of the high octane rating of the fuel.

Q: Can diesel vehicles be converted to CNG?

A: A diesel vehicle can be converted to run on CNG, but the conversion cost is higher than that of petrol vehicles.

Q: Why are exhaust fumes so small in CNG-run vehicles?

A: CNG is an environment-friendly fuel which is mainly composed of methane and its exhaust emissions consist of water vapor and a negligible fraction of carbon monoxide. The absence of carbon and other particulates result in negligible amount of harmful elements in exhaust fumes.

Q: How does large-scale CNG usage benefit the country?

A: CNG emits less carbon dioxide and contributes in lowering air pollution. It also helps in improving the Balance of Payments by acting as a substitute for imported liquid fuels, provides more business and job opportunities with the opening up of a new sector, and being competitively priced, it appeases motorists.