Three steps to save petrol in a CNG fitted car

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The new schedule recently implemented for the supply of CNG is clearly aimed at minimizing the availability of this fuel, since the total number of hours these stations are able to supply it, minus the time wasted due to electricity load shedding comes out to around just three hours a day. The station owners have stopped using generators since they are also facing a minimal income and it is no longer financially feasible to operate during hours of power cut.

The situation has made it impossible for most of us to receive this blessing of low cost fuel and is forcing many for the time being to use the precious commodity known as petrol, with the intention of reverting to CNG some day in the future. While we cannot do much in changing this scenario of CNG availability, some simple steps can ensure that we are making the most of our very limited supply of petrol that we can afford.

When your car is operating on CNG there are some changes done which lead to its economy and performance on petrol being adversely affected, reverting those for some time would make it perform at its peak on the primary fuel again.

Step 1 – Removing the air restriction:

In order for your car to run on CNG, its air supply to the engine is restricted a lot which means that when you convert it to petrol there is a shortage of air resulting in loss of both power and economy. The best bet is to avoid the most common method of applying tape after the box which contains your air filter and instead, getting a rubber or plastic restriction made which can be affixed to the end of air intake with a clip. This would enable you to remove it easily whenever you are driving on petrol and if you are lucky to get CNG then it can be fixed back simply.

If your setup has a venturi installed which also leads to a restricted air supply to the engine, you would need to remove it to reap maximum benefits for this duration.

Step 2 – Adjusting the plug gaps:

If you have no plans of standing in lines for many hours until the situation changes, you should also get the plug gaps to their original setting. For example, if the original gap at petrol was 1.1 mm then for CNG it would have been moved to 0.8 mm, reverting it would result in our intended target here i.e., fuel economy.

Step 3 – Letting go of that fat passenger in the trunk:

Removing the excess weight that you keep roaming around with i.e. the CNG cylinder, is quite a simple job and requires only opening some bolts. If you are at good terms with the mechanic then he would even keep it in his shop for the time you feel like putting it back. I am pretty sure that many people would have never cleaned the cylinder for removing the oil that gathers in it, so use this opportunity for getting that service performed as well.

All the steps mentioned above are a thirty minute job and would hardly cost Rs.500 through a local workshop, reverting to CNG setup would again require the same time and amount. Removing other parts of the CNG setup is not required since that would not lead to any advantage and they cause no hindrance in the top performance of your vehicle while it is operating on petrol.

Given that no relief is in sight in the current scenario, you would save much more and enjoy the noticeably increased performance at the primary fuel that you deserve by spending the precious petrol by emptying your wallet. Happy driving!

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18 Comments
  1. Junaid Aqib says

    one question?? do we need to remove air restriction in EFI models as well??

  2. Alina Gill says

    Yes offcourse

  3. Saleem Raza says

    Do we need air restrictions for CNG in EFI Models? what is the benefit of using air restrictions?

  4. Bilal Ahmad says

    It goes for all types of engines, in order to operate on CNG the air going inside the engine is restricted more then fifty percent usually. Ask your mechanic to show where it is in your car, between efi is a decades old technology and there is nothing too fancy about it 🙂

  5. Hammad Siddiqui says

    please this sort of info. must be published in urdu as well

  6. Malik Usman Ali says

    very informative for new bies and amateurs . Please note that if a car has ventury installed then normaly there is no need to choke the air intake by applying tape on the pipe of air intake . the mixture of gas released from power t and air intake can be adjusted manually and is set to the optimum level where engine idles smoothly .by doing this you wont have to change the settings for CNG and petrol every time you switch between the fuels . Venturi doesnt have THAT Much effect on the air intake as this air intake choking does. so go ahead and do it youself . its not that diffiicult as it seems to be , i have been tweaking the settings of my CNG kits since i bought my first CNG car back in 2001 (a 97 corolla xe) so i know what i am talking about . if u guys need help you can always ask me . i ll be more than happy to assist .

  7. Najmus-Saqib Malik says

    Ask your cng mechanic to adjust it without air block. I have city DSI 2003 176000 km driven and i am driving it on CNG without air block since last 2.5 years. clean spark plug on every oil change that is at 4000 km. clean air filter after every two week. Millage on one cylinder filled Rs. 700 is more than 240 without AC in ISB / RWP.

  8. Bilal Ahmad says

    Not aware of any good forum with considerable circulation for that, would love to do it though 🙂

  9. Bilal Ahmad says

    My personal inclination is towards a solution referred to as injector, always worked best for me. There are also may other tweaks but this was intended for optimizing petrol average 🙂

  10. Bilal Ahmad says

    If there is no air blocking then the ventruri would be restricting the amount of it going in, doesn't work otherwise.

  11. Najmus-Saqib Malik says

    NO, ventruri is like a ring between throttle body and black air filer box. I have seen it and there is not air block from that ring

  12. Muhammad Laman Samo says

    A well written informative piece by Bilal Ahmed 🙂 (Y)

  13. Muhammad Irfan Afzal says

    Thats why I left CNG long long ago

  14. Bilal Ahmad says

    I once had the same understanding about my ride, it came out that there was a restriction inside the pipe before the air filter. I was just not aware of its presence 🙂

  15. Najmus-Saqib Malik says

    hmm let me check with careful eye

  16. Tayyab Ali says

    yar yeh first point ko thora explain tou karo,kuch samagh nhi lagi yeh air restriction agar use hoti hai tou kyun use hoti hai ?

  17. Bilal Ahmad says

    Yup, I still remember the feeling I had when my myth was busted 🙂

  18. RAh EEl says

    same here just came back from petrol to cng..no tapes for air block and car is giving me about 220 km for 700 fill of gas i.e local in rwp isl ,and petrol around 16 km per ltr..cheers

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