CNG vs Gasoline?

Question

After visting these mentioned pages I found that CNG is better and more friendly than gasolene(petrol). But in day to day life the NGV (CNG veihcles) are found -> Very difficult to start on CNG in extreme cold and also it takes longer start time in normal conditions, so battery becomes dead quickly. Engine oil consumes rapidly, hence wears out engine seals earlier.
Pick and speed of vehcile reduces. Produce more smoke on cold start up. All these problems are not found while running on gasoline. Whats ur opinion?


http://www.barbotti.com/cng/advantages.htm
http://www.extraordinaryroadtrip.org/research-library/technology/natural-gas/ad-draw.asp

Answer 1

Maybe if someone did a bad conversion of an existing vehicle, you could get some hard-starting problems, but in general a CNG vehicle will behave at least as well as a gasoline powered one except in the range on one tank. Point by point:

CNG should start better in cold weather because it WILL volatilize. Heck, it IS volatilized as soon as it leaves the pressure regulator. Whereas gasoline can have a pretty low vapor pressure at -45F, even with a winter blend. (Note that I live in Alaska so this is something that comes up locally for me). All engines are harder to start in cold weather because the engine oil is thicker and therefore the motor is harder (needs more torque) to be turned. AND the battery can't put out as many amps when it is cold. This gets to be a an issue below about -10 with a new car (good compression) or with an older battery. It's noticeable on any car at -20F and every car ought to be plugged in (with block and battery heaters) below -30F.

Engine oil consumption should be the same. Oil in a CNG engine will look and be cleaner because there isn't as much soot formed in combustion and unburned hydrocarbons don't get in the oil. This is also true of propane-fueled engines.

Accelleration and top speed are a function of horsepower (and somewhat of gearing) and if two 150-hp engines are compared, they'll do the same. Whether the same displacement engine produces as much HP is partial a function of if the compression ratio is the same. CNG can be run in a higher compression engine and ideally is. The higher compression engine gives better power and fuel consumption than a lower-compression engine. But a dual-fuel (gasoline and CNG) vehicle HAS to be at the lower compression to accomodate gasoline use.

"produce more smoke" on start up. Not exactly. It produces more STEAM. Because methane (CNG) has a higher ratio of hydrogen to carbon than octane (gasoline), it makes a higher ratio of water to carbon dioxide. you never see the CO2 but the H2O is visible until the exhaust pipe heats up. It is MORE visible and last a bit longer in a CNG vehicle because the exhaust is essentially more humid. Not because there is more smoke (soot or oil blow-by or unburned hydrocarbons).

The lousy things about CNG are:

1) range (about half that of a gasoline-fueled vehicle)

2) time to refuel. If a station has a high-pressure (3,000-4,000 psi )tank, it goes quick. But if the compressor has to run to make a few thousand PSI, you have to wait much, much longer than for liquid gasoline to be dispensed. A home-sized CNG comressor takes many hours to fill a vehicle's tank. And costs $5000 or so.

3) There are few station to fill up at. So you have to do special trips or routes past that one station in your area. And there are some routes you just can't take because you'll be out of range of a filling stations which tend to be in larger cities plus a few on bigger interstates.

Answer 2

Cng Vs Gasoline

Answer 3

I read both links and found no evidence of greater oil consumption or harder to start in cold weather. Furthermore I have run oilfield engines on natural gas and the oil change intervals were greatly extended as a result, and with no excessive consumption. Both of those are unfounded. As far as smoke on startup, it is not smoke, but steam, which in cold weather steam comes out all exhaust pipes until they get hot. One advantage not mentioned is the oil will stay cleaner longer because there are no unburned hydrocarbons with CNG.
The main stumbling block to CNG is cost of conversion and storage. I know I don't want a tank on my vehicle with the pressures great enough to keep natural gas in a liquid state, which I understand to be about 900 psi. If I were going to switch, I would use LP gas.

Answer 4

The foremost reason anyone would prudently contemplate converting to CNG is economics. In weighing gasoline, for example, against CNG, the two largest areas of potential cost savings are fuel savings from different combustion efficiencies and different fuel prices. Examining fuel costs first, the two fuels must be compared on an equal basis. Often, published figures make such comparisons as the retail price of gasoline at full service stations with all motor fuel taxes included and industrial bunnertip prices of gas with no motor fuel tax (or no CNG permit cost) included, or city gate prices of gas with no tax, and with no capital charges for the refueling facility.

Answer 5

Petrol is always King, Cng would be nothing. If you use CNG the car will not run long like , say 8 to 10 years.