Fuelly Forums - Thinking about CNG

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Thinking about CNG

Compressed Natural Gas. It seems to be one of the cleanest fossil fuels available to power an internal combustion engine (from emissions, particulates, and overall consumption).

The Civic GX is a nice CNG vehicle -- but finding a used one that hasn't been beat to a pulp in fleet use is rare. The average range is 200-300 miles, which is about right for a week's worth of driving, and where I live, filling stations are close-by, and operated by the city of KCMO for their fleet.

So then, I started thinking about a conversion. I hear that it's common to retrofit Diesels to run on CNG, but what about gasoline engines?

Does anyone know if the 'Teg's engine can accept a retrofit, or would an entire swap be necessary (or even still, would the a used Civic GX be the most cost-effective CNG project)? From what I can see, 2 engines were made: the D17a7 up to '05, and the R18 series in '06+. I'd like to get their at-home fill-up device called "PHILL", but it is currently not available in my area. Just thinking out loud...

What are your thoughts on CNG?

RH77

Don't forget the d16b5 in the EK civic gx.

I say get one.

The d16b5 is essentially the civic hx d16y5 with a different intake manifold on it, so I would think the teg could get a conversion. You could always get a new gx, :)

I say do it... either convert or buy a new one. I knew a guy who sold conversion kits a while back. Wish I could remember his name. I'm pretty certain that you can convert a gas engine to CNG.

I would warn you though to keep a car for road trips. CNG stations are not as common as gasoline/diesel....unless you can just fill up at Home Depot :P

Is it easier to convert a diesel because then you don't have to mess with throttle plates, A/F ratios, etc?

I would go for LPG the range is alot better. Be sure and check insurance and state regulations. They make it so it's not as easy as it should be. If you tune just for LPG you can do pretty good on the range. Or you can go dual fuels and it not quite so good but it gives you a lot more options when you need fuel.

Like everything it has it's upsides and downsides. From an emissions perspective it's better than gasoline, but because CNG has a GWP of ~40 over the next couple centuries, depending on how much leaks while it gets to your fuel tank, it's way worse than just running straight gasoline for climate change. They flare stuff they can't capture because of this... Here's some more info. Don't quote me on this (back of the pad speculation, but then again everything I do is back of the pad), but I think it's suitability depends on how much escapes, at around 5% it's equivalent to gasoline in terms of GWP, but if it gets near 10% gasoline whips it's butt.

But how much would really leak from a GX tank?

It's probably not the car's tank for all intents&purposes... it's when it's coming out of the ground, piped/transported to the plant, purified, compressed, tanked and pumped into the fuel station's tanks. From the link I posted earlier.

Quote:

It is difficult to obtain precise figures of emissions. Global estimates vary between 25 - 70 Tg where 1 Tg = 1012 g or 1 million tonnes. This represents about 3 - 9 percent of all NG extraction.

So I'm guessing that on the low end it's about the same as other transportation fuels in terms of GHG emissions, and on the high side, probably worse. Check out the emissions section of the link I posted earlier, it has more info that you probably want. Also, if you check out the Calculation of total climate change effect section, the author states

Quote:

However, this comparison is not strictly fair, because the carbon dioxide produced during the mining and transport of the anthracite has not been calculated in. Nevertheless, even if we add an extra, say, 15 percent for this, natural gas produces more greenhouse gas than coal when viewed holistically.

Which implies that NG likely produces more GHGs than gasoline, since coal is just about the worst in terms of GWP per kwh iirc. In terms of just electricity generation NG is behind both coal and fuel oils, but because it has such a high GWP (60 for the first two decades) if we look at the entire operation, extraction, etc... it becomes the largest source of GHG/kwh simply because if just 5% escapes, the GHGs/kwh go up by roughly 25%.

I wonder, the GX always wins the aceee greenest car award, and they do a well to wheel approach on things...I wonder if they have a longer report that might include this...

Probably not, since it's both hard to figure out, and not very flattering for CNG's image. First world countries seem to be green washing themselves by spreading out the externalities over the rest of the world. :(

Quote:

Natural gas is not the least polluting of fossil fuels, as the large oil producers would have us believe. In terms of purity, it is good, but greenhouse gas emissions are holistically very high from its use. It has been proposed as a substitute for petrol in internal combustion engines, but it is believed that this will increase greenhouse gases, especially as the disconnection of pressure hoses at filling stations will inevitably release raw methane into the atmosphere.

Many approximations have been made in these calculations, but these have been made conservatively and in good faith. Unfortunately, accurate data permitting a better calculation are not available.

I conclude that the use of natural gas would be better curtailed if we are to improve our record for greenhouse gas emissions. As a final word, methane concentrations in the atmosphere have increased to 2.25 times the pre-industrial level, compared to only 1.3 times for carbon dioxide, entirely due to man-made causes. As the atmospheric residency time of methane is only a small fraction that of carbon dioxide, even with low hydroxyl radical concentration, cutting emissions would have a much faster effect on reducing climate change effects than cutting down on other fossil fuel combustion.