Converting a gas SUV to CNG

[tmacc]

So how difficult is to convert a injected gasoline engine to CNG? Our carpet layer has an older Dodge van that's been converted. Carburator probably. Doesn't work very well in the winter though. We live at 7000', so maybe that needs to be taken into consideration as well.

 

[TAbbott]

Are you sure you don't mean LPG -- Propane? CNG requires extremely heavy tanks, as it's stored at very high pressures. I've seen some class 8 trucks that were converted, but they started out as diesels.

 

[tmacc]

Isn't CNG what they sell at some gas staions? The decals I see on Questars vehicles say CNG. They is one station in Park City, UT not far from our house that sells it.

 

[TAbbott]

I think the tanks available for CNG are basically like welding cylinders. They have to be capable of holding something like 3600 psi of pressure. CNG contains fewer btu's per liquid unit than does gasoline, so fuel mileage will be less -- by about 40% as I understand it -- and because of the limited size of the tanks your range won't be much. Google CNG tanks and you'll find the largest lightweight composite one made for the automotive industry (buses and truck, primarily) that holds the energy equivalent of 40 gallons of diesel fuel but is 21" in diameter and 120" long. It wouldn't even fit in the bed of a pickup truck. Downsized so it would only be 95" long and 21" in diameter (fit lengthwise in a standard 8' bed) it would only hold the energy equivalent of 31. 6 gallons of diesel. I wonder how practical a cng vehicle could be for general purpose use.

 

[tmacc]

OK, it may not be practical to convert a Nissan Xttera due to the size of the cylinder required and the limited range. Just a thought. The carpet layer I talked to gets about 150 mile on $7 worth of CNG. He called me today and said that he's still figuring out the range thing and ran out of gas. I'm not sure it's dual fuel either.

 

[gregdoerfler]

I would also like to know about converting a vehicle to cng as I get free gas.