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How Natural Gas Fuel Powered Cars Work

How Natural Gas Fuel Powered Cars Work

By Jeff Youngs, August 10, 2012
Natural-gas-powered vehicles burn compressed natural gas (CNG) instead of conventional gasoline. As with gasoline, CNG is mixed with air inside of an engine's cylinders, is ignited with a spark plug, and the resulting explosion moves the pistons and propels the vehicle.

The benefits of CNG are lower operating costs, lower fuel costs, improved gasoline-gallon fuel economy, and almost zero smog-forming emissions. One example of a vehicle that uses CNG for its fuel is the Honda Civic Natural Gas Sedan. As a result of its clean-burning nature, this vehicle qualifies for single-occupant carpool lane access in several states, which is an added benefit. That alone might be worth paying the price premium for the Civic Natural Gas, which costs $27,095.

To make the Civic run on CNG, Honda replaces the conventional gasoline tank with what it calls a "safety-engineered, aluminum-lined composite fuel tank" rated to handle 3,600 psi of pressure. The tank is located behind the back seat between the rear wheels, and holds the CNG equivalent of 8 gallons of conventional gasoline.

Refueling the composite fuel tank of the Civic Natural Gas Sedan's tank, owners must find one of the estimated 1,300 public CNG filling stations in the United States. Filling the tank using one of these pumps takes no longer than a traditional gasoline-engine vehicle. Alternatively, Honda offers a home fueling system that the company calls "Phill," which taps into a home's existing natural gas lines. This type of refueling system is a slow-fill design and can take several hours to fill the CNG tank.

In order to run on CNG, which has a higher octane rating than gasoline, the Civic's 1.8-liter engine is designed to have a higher compression ratio, which is 12.7:1. Additional modifications include special fuel injectors, intake and exhaust valves, and valve seats; unique pistons; and strengthened connecting rods and crankshaft. Beyond the engine modifications and fuel holding system, the Civic Natural Gas model is outfitted just like a traditional Civic LX Sedan.