CNG is gas, but not the smelly after-dinner kind despite methane being a prime component. It’s supposed to be good for the environment but not so good for the car engines. It’s even worse for those of us who like to use our cars only to keep the tire manufacturers in business. But are the myths all true?
The debate regarding CNG goes on in many confused ways. Some say it's good, some say it’s great and some say it’s terrific. That’s all good it seems. But some say CNG is a life hazard for people but more importantly a hazard for your car. It petrol wasn’t the status symbol it is now, then we’d all be driving our cars on it. But most of us are miserably poor so CNG seems an attractive option.
Following are some relevant points based on personal experience, web site info and an uncle who’s a senior chemical engineer at Chevron who really knows his gas (pun intended).
Safety concerns 
CNG is apparently safer than petrol. In case of leaks, being lighter than air, it rises up and dissipates into air. Other fuels form puddles for movie action heroes to throw a lighted match in.
Also CNG has a 700 degree Centigrade ignition temperature compared to 455 degree Centigrade for petrol. Now that’s what I call cool info.
Storage is far safer as CNG cylinders are designed from a single piece of special steel alloy with no welded joints. One piece equals structural strength. So what’s with all these news stories of tanks bursting? Substandard cylinders that are NOT designed for storing CNG or expired units with hairline fractures. That’s why regular checks are a good precaution.
As for sudden impacts or overfilling, a ‘burst’ disc ensures safety as the disc ruptures so no excess pressure situation over the specified level is created. Each cylinder is tested as per international specifications before being installed. Italy, New Zealand, Argentina and the US are countries where CNG has been in use for years, and it has been ategorized as being safer fuel than petrol.
Know what you’re getting 
CNG cylinders have an expiry date. They are extremely tough and have safety valves that allow gas to escape in case of sudden impacts. I saw a burned Probox in front of Dhanmondi thana where the cylinder was still intact. Reason for fire was ‘agitated students’. The point to remember is DON’T use cylinders sold to you under a street lamp in Bhooter Golli after 1AM by someone named Munshi Baatpar. Get your warranty. If you want to feel extra safe, get a small fire extinguisher (available at Tejgaon).
Does CNG harm engines? 
If you’ve read this far, THIS is what you really want to know, isn’t it? Here is where arguments heat up. Many say CNG kills engines, I’d say we do the killing ourselves due to lack of proper care. Apparently, according to experts (NOT me), CNG serves to extend life of lubricating oil as CNG will not contaminate or dilute crankcase oil.
Fouling of plugs is eliminated and plug life is enhanced as CNG does not contain any lead. CNG enters the engine as gas while petrol comes in as spray or mist which washes down the lubricating oil from the piston ring area to raise the rate of engine depreciation. This reduces maintenance costs and engine life goes up. Now these are all scientific theories and I’ve seen several opened CNG engines that look fresh.
What you HAVE to watch out for is the extra heat generated that cause oils to break down over time. The advanced timing contributes to greater heat generation as far as I know.
My gassy car stories 
Regular maintenance does wonders though. Plenty of CNG cars in my family. My brother’s Sunny 1.5 has been running for more than 4 years now. Oil leaks but pulls hard fully loaded. The other brother has a 91 XE Saloon 1.3. Pulls like a wussy but running for 2 years with AC working at all times. My buddy’s 91 TX carbureted 1.5 runs like crazy on same engine for the last 6-7 years. I’ll let you know how good a condition mine is in about 2-3 years. Look for this post then.
CNG makes Captain Planet happy? 
Being a natural gas (methane content) its exhaust emissions contain just water vapour and minuscule quantity of carbon monoxide, no carbon or other particles.
But can all this make you Fast and Furious? 
Power loss of 5-15 per cent means that acceleration is slower which can be partially eradicated with proper tuning or the latest generation CNG kits. Also, torque suffers hence CNG cars with smaller engines have a tough time climbing slopes.
So petrol is completely redundant?
‘Occasional use of petrol serves to lubricate the carburetor besides making for better running of the engine’. That’s a quote direct off the site.
Has the CNG movement fared well in developed or developing countries?
Another quote - Having been around since the 1920s, Italy has 240 stations and 300,000 cars running on CNG, New Zealand has 250 CNG pumps and 250,000 vehicles. Argentina has undertaken a major CNG programme and has 700,000 CNG run vehicles. Thailand, Indonesia, Bangladesh, Canada, France, Pakistan, India, Holland, Australia, UK and the US have also taken to CNG in smaller measure. Availability of natural gas and socio-economic conditions are the two factors conducive to bring about switch to CNG fuel.
For further text-bookish, boringly written details, check the following links:
THE CNG OPTION
CNG* an alternative fuel
Adani CNG
The Advantages and Disadvantages of CNG Conversion Kits
Here's a link that explains each CNG component and how one size DOE NOT fit all
http://www.ngv.com.my/print.asp?id=336
previous WheelsBD post about CNG FAQ
28th May 2009, 03:24 PM
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