Compressed Natural Gas--Compatible? Fiery Death Imminent?
 

As much as I like to say "I am an engineer," there are things that I simply do not know. Lately, there have been some commercials on the local radio that are suggesting that cars can be converted to run on Compressed Natural Gas (CNG), and in fact, a lot of the RTA buses and some service vehicles run successfully on CNG with no problems. For reference, Gasoline/petrol has an specific energy (in MJ/kg) of 44.4, while methane/natural gas comes in with a value of 55.5 (couldn't find if there is a difference between CNG and uncompressed).

So then my mind turns to our cars. For those of you who know our engines, could they be 1) Successfully converted to run on CNG, and 2) what would be the possible pros and cons? With a higher specific energy, I would imagine that its possible to generate more power, or possibly burn more efficiently.

I looked around, and couldn't find another thread like this. So, my fellow engineers/gearheads, what do you think?

LOL Fart powered cars was the first thing that came to my mind

I have seen a few UPS vans and what not say the run on CNG around here too. I don't think its something you can easily retrofit but not a bad idea if you design the engine that way from the factory

It's not worth it. It costs thousands to properly convert the vehicle over.

If you want a CNG vehicle, just go buy a new Honda civic built that way from the factory.

Also, have you heard of Google?

I recall a few years ago when I was working at a Krown shop, a guy with a 200-something Chevy Silverado SS came in. It was converted to CNG. Surprised the hell out of me. I don't think it would be terribly hard to do a retrofit, probably need a fuel cell, regulator, fuel rails, injectors, ECU flash, new fueling logic, and some more stuff. Basically replacing all of your fueling system.

SOURCE

Yes, it can be done.
No, you can't/shouldn't do it yourself because you will most likely run afoul of the Clean Air Act, with a fine of $5,000 per day driven. (Source: Popular Mechanics)
It will be expensive and there is no ROI

I'd love to have a CNG car, particularly one I could fill at home (another expense have to have a compressor) and have to fill directly to car which takes hours.

Kinda on topic but...

My grandfather put a propane engine in a Oldsmobile he had. The whole trunk is a tank and the car nearly scrapes on the ground form the weight in the back it is slow as ballz but he has drove across Canada a few times with it

Conversion of petrol engine cars to gas is rather popular thing here. Simply because it means halving fuel costs. Most taxis here are converted. Many big volume engine ones are (one thing is slight performance loss from already too powerful one, another - from some 1-1.5Kcc smallish engine with often inadequate power as is). No clue though how much it may cost to do for ours, as i find milleage acceptable as is and don't want to add any extra weight (rather removing some :)) and loose space from already small boot. When at some time in past i considered some 350Z aswell prior finding good deal on GT86, i thought it may benefit from LPG kit though :)

Look at my OP, I never asked about feasibility, just if it could be done to our cars. My thinking was that it would be an interesting project considering our non-traditional engine.

And yes, I have heard of Google, I use it frequently. However, that wouldn't generate much discussion and thinking here on the forum, would it?

This is all true--again, just an interesting thought if our cars could be converted to CNG, and what gains may be made from using a different fuel (similar to the E85 crowd--lower mpg, higher power. Would CNG be the same or opposite?)

And that makes a lot of sense over there, especially as NG is dirt cheap right now compared to the petrol prices you see there. You make a valid point that this could add more weight to the car, could throw off handling a bit.

Havent You???



http://lmgtfy.com/?q=Does+HunterGree...w+about+google


(you DO know that telling someone to "just google it" has become waaaay unfashionable?)


http://lmgtfy.com/?q=telling+someone+to+google+it

Yes, I reckon the engine in the FR-S could be converted to burn natural gas ..... after all, it is a internal combustion engine.

Pros, less expensive to operate; cons, high cost of conversion.


So, there ya go ...... ;)


humfrz

On second thought .. is NCG meant same as LPG? I hope i haven't joined conversation with argument about apples when it's about oranges.
As for LPG kits, IIRC costs of kits depends on injector count .. and i wonder if ours having dual injecting fuel system with DI & PI won't complify a bit things ..

From what I've read, the performance goes down, not up, but there may be ways around that. What you probably won't get around is the heaviness of the tank and fuel, well really the tank. The articles I read said you can expect about a 10% loss of power although the fuel economy can stay the same if installed properly.

From what I recall 120 cubic feet (uncompressed) is equal to 1 gallon of gasoline. When compressed that weighs about 5.5lbs which is a little less than a gallon of gasoline. If you wanted a tank for more than just a track run though, it would take up a good portion of the trunk. A typical 15 GGE tank is 19 inches in diameter and 60 inches long. The lightest tank for a 15GGE would be a plastic/carbon fiber wrapped tank that weighs around 100lbs and costs several thousand dollars. Source here.

.

Nope not the same thing.

Upsides:

• Lower fuel costs
• Reduced emissions
• Better specific energy (energy per unit of mass)
• 120-130 octane
• Depending on your state, you might be allowed to use HOV lanes without a passenger

Downsides:

• Conversion costs are high
• Filling is not as convenient as gasoline
• Off-the-shelf tanks are very heavy and take up trunk space.
• Much lower energy density (energy per unit of volume)
• You'll have to put an ugly sticker on the back of your car

That out of the way, pretty much any car can be converted. Our cars would probably do pretty well with it given the high compression ratio. Even so, I would expect to lose power without FI. The specific energy (energy per unit of mass) is higher, but its energy density (energy per unit of volume) is much, much lower so it requires greater compression. Direct injection could help, but AFAIK that technology is very new and not offered in generic conversion kits.