The 2015 Chevrolet Impala will feature optional bi-fuel capability. Using compressed natural gas, it will offer a 150-mile range. A gasoline fuel tank will provide an additional 350 miles. (Source: Chevrolet)
All good points. I would considered setup of the infrastructure the big concern for the CNG vehicles followed by the CAFE standards. Well hopefully there is motion in both categories for this new vehicle initiative.
Right now, Rob, the makers of these vehicles work with outside suppliers to install the fuel tanks and plumbing. And that can add $9,000 to the price of a vehicle (bear in mind, Chevy has not announced this for the Impala). But I do believe that higher production volume would enable automakers to do this on the production line and cut a lot of the cost.
Rob, not that kind of cool, reaklly. A Hemi-Cuda with a 426 and a huge blower and 18 inch wide slicks in back is cool. But any papers showing what it cost are not. WE are not talking about MY opinions of cool, but rather those masses. Definitely not engineering types.
Good info, William K. And your comments underscore an earlier question I posed in this thread. Why haven't natural gas cars become more popular? Is it just the infrastructure? Car companies are not pushing these cars they they're pushing hybrids and EVs. Are there underlying reasons?
Rob, that is a different question and easier to answer. Even a non-optimized CNG fuel system would provide a real cost savings, at least until the government figured out how to tax it enough to make it non-competitive. And due to lower combustion temperatures it would certainly produce fewer nitrogen oxides. So there is a real benefit. But it is still a combustion process burning hydrocarbon fuel, so that "carbon footprint" issue is still attached. But unburned fuel emissions would probably be reduced, and the exhaust would definitely smell better, so there would be a real emissions benefit.
The challenge now, as in 1970, is that natural gas and liquid propane are both used for heating purposes, where the sales have a completely different pricing structure. And even in 1970 the feds were concerned about how to tax folks who pumped up their gas tanks at home. It seemed vital to them to collect that extra tax even back then.
It should be possible to optimize an engine for best efficiency with natural gas. And direct injection would certainly allow mor variation if needed. But it would include valve timing, ignition sprk timing, airflow patterns in the combustion chamber, and injection timing. This amount of optimization would take some real effort and expense. There are companies that claim to have done some of it, I don't know how much has actually been achieved, and they are probably not wanting to discuss it. One interesting application is the natural gas powered generator set, which runs at a fairly constant load and a single speed. That one may already have been optimized.
But being optimized to the "best possible" is no promise that it will be very efficient, but only as much as it can be.
William K, I wonder if the inefficiency of natural gas vehicles comes because most of them are conversions from gas engines. If the engine was designed specifically for natural gas, wouldn't tend to be very efficient?
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