Saturday, July 18, 2009


With rising cost of petrol , I was wondering whether switching to CNG would be a solution to cut cost.

So I did some research, on CNG and surprisingly found that it is indeed cheaper and safer than petrol! , AND IT ENVIROMENTALLY FRIENDLY.

Yes, like many of us, when it comes to gas, we have this phobia of explosion and leaks. But you will be surprised by what I found out.

Just take petrol for instance:

I found out that it takes a temperature of 455 C to ignite.

Guess the temperature needed to ignite CNG?.... a whooping 700 C!

Yes almost double that of petrol….

For a comparison of how hot is 700 C , I did some research and came up with this: let take the common everyday cigarette. This is what I found out.

Temperature of a lit cigarette = 400 C (at outside) / 580 C (at the middle)

But during drawing in the smoke, the temperature will increase to 700 C (at the middle).

So looks like CNG is safe indeed! For those of you interested on some FAQ, please read on and knowledge yourself this the information. It is quite detailed , will take 10 to 15 mins of you time…….cheers!


CNG is abbreviation of Compressed Natural Gas

When we compress or pressurize the Natural Gas to 250 Bar pressure then its called CNG. Natural Gas or CNG consists of at least 85% methane and 10% of nitrogen and carbon dioxide. It belongs to the same group of organic fuels like crude oil and coal.


Because at ordinary pressure, the quantity of gas filled in cylinder will not be enough for long distance running. That’s why it is compressed to 250 Bars (the pressure of Natural Gas in homes is 0.13 Bar)


There is 40 to 50% saving to the pocket, by running car on CNG instead of Petrol.


CNG cars give out 90% less carbon monoxide, which is a poisonous gas and causes global warming and climate change. Also, unlike Petrol, CNG doesn’t have lead emission, which is harmful for health. Thus, CNG usage ensures a cleaner air by reducing poisonous exhaust emissions. CNG operated vehicles can meet the highest emission standards around the world (as big as the EURO 4).

CNG is pollution free. Its exhaust emissions consist of water vapors and a small fraction of carbon mono-oxide. There are no black carbon, sulphur and other particles in the exhaust, like in Petrol.


YES. There are 06 reasons that why CNG is a safer fuel than Petrol/ Diesel/ LPG.

  1. CNG has specific gravity of 0.59 (lighter than air) so in case of leakage CNG just rises up and dissolves into atmosphere. On the other hand, Petrol, Diesel or LPG after leakage, will form a dangerous pool below the car, which can catch fire.
  2. CNG ignites at temperature of 700 C while petrol at 455 C, which means Petrol can burn more easily and is unsafe.
  3. In case of leak, if CNG concentration in air is less than 5% or more than 15%, then CNG will not burn even in presence of a spark. However, Petrol has no such limit, and it will catch fire rapidly by a spark.
  4. CNG cylinders are designed and built with special materials to the highest safety specifications, which make CNG storage far safer than petrol tanks (which are generally made of plastic).
  5. CNG is not poisonous and it does not contain toxic substances or other cancer causing contents.
  6. In case of an accident, you are safe, because the CNG cylinder is thousand times stronger than a Petrol tank, because it is made of steel. Also, once the pressure of gas exceeds a certain limit, the valve at the cylinder automatically shuts off, thus avoiding any leakage.


Almost every Petrol car can be converted to CNG. The conversion of carburetor vehicles is easier and can be done in 2 to 3 hours. However, for EFI Cars (Electronic Fuel Injection) conversion takes a longer time because of many electronic parts.

Converting a vehicle to run on CNG involves the fitting of a CNG Conversion Kit, CNG storage cylinder and associated equipment to allow the gas to flow into the engine.

With a switch on the dashboard you can switch between using Petrol or CNG. Therefore, the car can run on petrol if CNG is not available. By default, the car switches to CNG. When the cylinder has been depleted, it will switch to Petrol automatically.

Further more, whether you decide to use CNG or petrol is not a hustle at all. Even while you are driving, there is no need to stop or to switch off the engine. Feel free to press the switch any time.


YES. There are 06 reasons:

  1. CNG is natural product, it doesn’t have any chemicals/ lead/ sulphur to harm the engine. The Octane Number of CNG is 130 as compared to 98 of premium motor gasoline.
  2. CNG does not contaminate and dilute the crankcase (like in Petrol), so Lube oil life is extended considerably
  3. CNG doesn’t have any Lead (like in Petrol) this increases the life of spark plugs preventing plug fouling.
  4. Petrol or Diesel enter engine in form of spray, washing down the lubricating oil from piston ring, resulting in depreciation of engine. But CNG is gas and it does not wash off the oil, thus increasing the life of engine and reducing maintenance cost.
  5. When gas fuel is used, no carbon is formed during combustion and engine stays very clean internally.
  6. CNG has a good mixture distribution quality, which improves the combustion efficiency of the engine.


CNG consumption depends on the size of the engine. However, since 1 KG CNG has more energy than 1 Litre Petrol, the consumption of CNG is lower than that of Petrol under equal conditions.

Example: A car (1.6L) consumes about 5.8 litres of CNG per 100 KM. This cost about S$6.60 (at 1.25 SGD per kg)

Compared to petrol , a car (1.6L) consumes 7.1 litres per 100 KM. This cost about S$14.50 per 100 Km at present fuel price. More than 50% savings!

1 kg CNG = 1,1 litres Petrol (under 200 bar pressure)


There is a narrow power loss of 5-15 % which can be minimized by proper tuning of the CNG kit (e.g. advancing the spark timing). The power loss on CNG is generally not noticeable while driving on highways.


NO. The equipment is not complex and gives trouble free service for years. However, to maintain maximum efficiency it is advisable to have a routine check by an authorized technician after every 10,000 KM, just like in a petrol engine.


Sequential Gas Injection System:

This advanced gas injection system can be installed in all fuel injected vehicles. The system is fully homologated in compliance with the latest safety standards for gas fuel systems (R110) and keeps the emission in the expectable range established by the strictest standards (EURO 4). This system has the following parts:


The ECU is controlled by a microprocessor which automatically detects the optimum combustion parameters and constantly monitors the engines operating conditions checking the various parameters like petrol injection time, gas pressure, gas temperature, regulator temperature. It also determines the right volume of gas to be injected, thus reducing emission and extending the life of the catalytic converter. Other functions are the automatic switching from gas to petrol and vice-versa.

Injector Rail

The injection unit ensures that the right quantity of gas is delivered into the intake manifold at the intake valves. The electronic injectors are opened in the right sequence and at the right time to suit the engine's ignition cycle.
The ECU provides the injector with electrical signals necessary to precisely regulate the gas flow to the cylinder.


The regulator reduces gas pressure from 200-220 bar to 1.8 bar. The reducer unit is a water-gas heated two stage, servo-assisted membrane unit. A solenoid valve shuts off the gas flow to the engine, when the engine is not operating.

Gas/Petrol Fuel Switch

This is the electronic switch that is connected to the Sequential Gas System. The switch allows toggling between CNG and petrol and spots a 5-leds level gauge showing the amount of gas remaining in the tank.


It is made of steel and it’s thousand times stronger than you present petrol tank. It comes in few sizes, 30liter to 99liter.

The cheaper tanks are made of lightweight steel, the you have a more expensive type made of composite material.

Potential buyers also have to keep in mind some disadvantages of the CNG conversion, is that, the cylinder or the cylinders are installed in the boot of the car, which means, that the storage capacity in the boot is reduced.

The cost?

It cost about s$3600- s$6000 to fix the system. That means, if you spend about S$450 on petrol a month, within 18 months, you recover the cost and after that you fuel bill will be 50% cheaper. But the draw back is the lack of filling stations providing CNG filling in singapore, but i believe if more cars convert to CNG, the demand will natually push regular petrol stations wanting to join the bandwagon

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