There have been gas vehicles that are dual fuel CNG. Ford Contour and the Jeep Cherokee are two I know of. I am sure there are others. I would say that finding a filling source would be a problem in most state. I looked into this. California and Oklahoma seem to have more than a few CNG stations. When I looked into it. Indiana only had two. I think the conversions were $1500 to $3000. I did some math at the time and I would save about $400 per 15,000 miles.
Tom

We are talking about here in the US.

If the private sector saw an opportunity, they would be doing it now.

Just because the technology is doable doesn't make it feasible, or practical.

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MB-less

CNG has about a 30% lower volumetric efficiency than gasoline.
The tank might be heavier but not when you include the fuel.

Also, natural gas runs .6 - .65 the density of air.

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MB-less

I think not. Propane turns to gas when not under pressure.

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MB-less

The empty tank heavier, the fuel lighter but requiring 30% greater volume to get the same miles/tank? So the tank must be larger to accommodate the the reduced efficiency adding more weight?

Does natural gas cost 30% less? Is it subject to the automobile fuel taxes?

I dunno.

To the question, yes these conversion cars can be run on both regular gasoline and propane. I asked this question some weeks back about propane.
Not this week, but next week I am going to the propane dealer that offers this conversion to check it out more thouroughly here. Gasoline just hit $4.76 a galon.

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Insanity: doing the same thing over and over again and expecting different results.

2006 - Suzuki Gran Vitara (2.0 L fully equipped) Like this car so far except for trying to put on the seatbelt.
1988 - 190e - 2.3L - 172K miles (It now belongs to the exwife)
1999 - Chevy Blazer LS Fully Equiped - killed it June 2006
2001 - Honda Civic EX - 68K miles (sold June 2004)
1963 - 220S - Dual Carb 6 cyl. (sold)
1994 - Yamaha WaveRaider (fun to ride)

Bot is correct the BTU rating for CNG is far lower than gas or diesel. The storage pressures in a CNG converted vehicle are currently 3600psi. a normal cylinder will give about 6 gallons equivalent. dual fuel vehicles are available but none of the current OEM's offer them. Depending on tanks capacity you will get about 65 to 150 miles on CNG system and the current cost to convert a normal gas vehicle is around $30K. The tanks are super expensive. now LPG (propane) is a very viable alt fuel, BTU rating is at or better than gas and diesel and it is stored under much less pressure. Clean Fuels USA offers a system for the medium truck market for about $11K that uses the 8L GM gas V8 and it runs like a spotted ape. the fittings to refuel can be found at any propane company found in any small town. I am currently looking into moving some of our fleet to this since the current cost per gallon of LPG is $2.00.

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Keith Schuster
2006 E350 98K miles
2013 Ford Explorer 15K miles

I've heard that some of it has to do with EPA approval. It cost a bit to get EPA certification. One of the US sellers only does off road vehicles. I did look into this probably 3-4 years ago, when gas first spiked to over $2.00. With road tax, it cost about the same. CNG mighthave a bit of an advantage, but not many filling stations in my region.
Tom

I don't think it is taxed - yet. I read somewhere the equiv $/gallon is about 2.15 at the moment.

30% less volumetric efficiency does not translate directly into its volume in the tank, its the volumetric efficiency of the engine for the fuels. Its hard to explain, but you do need more CNG to get the same power you get from gasoline, but the method of getting the CNG in the engine and how long that takes is pretty important. Remember, horsepower is calculated (not measured) by integrating the torque curve with regards to time. There is an approximate formula to go from torque to HP, but i am wandering here.

The octane value of CNG is about 130. You can get back a lot of the lost power by forced breathing. You sure won't detonate at 130 octane.

Also, to the other poster mentioning having a dual fuel setup, there are issues there. The main one is having to have 2 fuel tanks. Say goodbye to your trunk. If you have a CNG only vehicle, you can replace the gasoline tank with the CNG tank under the car.

The other big issue is you need to tune the engine for the fuel you are running to get the maximum efficiency. To run dual fuels you have to compromise on the engine settings, so neither fuel will run optimally. I am guessing you would need to reprogram for the CNG, not sure how that is done or if every car can be easily modified.

I am contemplating a CNG conversion on a 108 car. The car is < $2000 so I don't care what the CNG kit costs. My holdup has been trying to find a fuel station. The home compressors are expensive (around $3k).

Fred

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MB-less

LNG should have a much greater Carnot efficiency than room temp gasoline. Right? So somebody has to put energy into the system to get LNG. That would be the supplier so the cost of compression has to be figured in.

Hey, in the summer you could use the decompression of LNG as a heat sink instead of running the A/C!

B

I doubt a car would pull the gas fast enough to provide cooling.

For my 914 project I am thinking of hooking up a blower to blow air through an ice chest and onto me, like the racers do in their helmets, except mine would be without helmet.

Cheaper than an a/c add-on and I guess we better get the ice machine fixed at work.

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MB-less

Also use it as coolant for an intercooler?

B

My car is a high compression Chevy 327, so no intercooler needed!

Actually several years ago some racers used a/c compressors hooked to intercoolers to achieve high levels of turbo boost. The first problem was a/c compressors self destruct an race RPM's, so you had to run them off tranny half shafts with gear reduction. Second was it worked very well and was outlawed by sanctioning bodies.

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MB-less

I'd bet a shiny nickel that any savings gap will close quickly. Our last forklift fuel delivery was up 12% over the one the first week of April.

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1980 300TD-China Blue/Blue MBTex-2nd Owner, 107K (Alt Blau) OBK #15
'06 Chevy Tahoe Z71 (for the wife & 4 kids, current mule) '03 Honda Odyssey (son #1's ride, reluctantly) '99 GMC Suburban (255K+ miles, semi-retired mule) 21' SeaRay Seville (summer escape pod)

I should know this but back to the question if LNG or CNG is taxed, not sure, but propane is. In 1979 I worked with a guy in Midland who had a propane pickup (dual fuel) and when you bought the propane you paid some sort of tax and they gave you a tax receipt. If you got pulled over and didn't have the receipt, you could be in trouble. I guess they figured you could steal propane from other tanks, or even someones grill if you had the proper hoses.

I always wondered how they measured propane into vehicles. For gas grills they weigh the tank before and after, I know they don't do that on cars.

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MB-less