GM engineers bullet-resistant CNG tank for bi-fuel Impala

Will we be seeing more CNG cars being that “clean natural gas” is so plentiful these days?
Is this car good reason to buy GM’s version over a do-it-yourself conversions?
This is of course more of that “all of the above” approach. Others might like to see the effort spent on electrification.

Chevrolet has gone to great lengths to ensure the safety of the Impala’s natural gas tank.

The company stated being able to take a bullet and withstand fires from multiple directions sets apart the compressed natural gas (CNG) tank in the 2015 Bi-fuel Chevrolet Impala from less-strenuous testing of other natural gas-powered vehicles.

height=”409″ />Chevrolet explained a large piece of cast aluminum helps protect the tank valve and connection from certain side impacts while sheet metal plates on either side of the tank help protect it from loose objects in the trunk or rear seat.

“We designed this system for those ‘what if’ situations,” said Nichole Kraatz, Impala chief engineer. ”The customer shouldn’t even know it’s there. They shouldn’t even think about it. CNG should just be another fuel they use to power their vehicle.”

According to Chevrolet, durability and safety testing at the tank’s normal operating pressure of 3,600 PSI and higher subjected it to normal and extreme situations, exceeding federal requirements and CNG industry guidelines. The company gave these test protocols as examples of what the tank can withstand:

• The industry-standard Bonfire Test confirms the CNG tank’s pressure relief valves are operational and help prevent the tank from rupturing in a fire. In addition to placing the tank about four inches above a steady 800-degree Fahrenheit fire, General Motors’ engineers added trunk, back seat and underbody fires to test the pressure relief valves’ ability to sense heat on all sides of the tank. And the tests were done at two different fuel levels.
• In the Penetration Test, the tank is filled to its service pressure and is shot with a 7.62 mm armor piercing bullet. In order to pass the test, the bullet has to pass completely through one side of the tank without exiting out the other side. The goal is to have the tank maintain the bullet hole only as the weak structural point, without rupturing.
• Front barrier, side impact and rear impact crash tests were conducted on the Bi-Fuel Impala. Some aftermarket CNG-conversion kit manufacturers conduct only a barrier test.

The tank also undergoes long-term structural integrity tests equivalent to 15,000 pressure cycles and hydrostatic bursting tests of up to 8,100 PSI, added Chevrolet.

The Bi-fuel Impala runs on both CNG and gasoline; it is available to order now through all Chevrolet dealerships in the US and Canada with delivery expected at the end of this year.

Chevrolet stated the all-steel trunk-mounted CNG tank holds approximately 7.8 gallons, sufficient for about 150 miles of driving after which the Impala seamlessly switches to gasoline power.

Chevy And GMC HD Pickups Get CNG Package Pricing

Truck owners looking for a cheaper alternative to diesel can have it for a $9,500 premium on Chevy and GMC heavy-duty pickups. GM figures you can save about $2,000 a year using CNG twice as much as gasoline, which means it’ll take just five years (or about 100,000 CNG-powered miles) to recoup the cost. Worth it?

That depends entirely on where you live. Some areas of the country are inundated with publicly-accessible CNG filling stations; other places don’t have a CNG station within hundreds of miles. Of course you’ll have to sacrifice some power if you choose to run the cheaper fuel. On gasoline, the 6.0 liter V8 is good for 360 horsepower and 380 ft-lbs of torque, but running CNG it churns out just 301 horsepower and 333 ft-lbs of torque.

Having begun production back in 2012, GM is sticking with its long-term cost analysis for its CNG vehicles. To get the kinds of savings GM claims, you’ll have to drive an average of 27,000 miles a year, more than twice the national average, and 19,500 of those miles must be on CNG fuel alone. For major fleet operators, these numbers are definitely attainable. For the average guy looking to save a few bucks though, this truck would require over a decade of driving to make any sort of financial sense. Much of the cost is tied up in the expensive fuel tanks, and while companies have made efforts to produce better storage options, these are still years away from making an impact.

For those wanting a CNG van instead of a pickup, the CNG system will cost a bit more, starting at $10,825 for a three-tank system and $12,090 for the four-tank system. So far, no word on the rumored Chevy Impala CNG either, though Ford is said to be working on a small fleet of CNG vehicles as well.

Nobody ever said going green would be cheap, and unless you own a fleet of these trucks, you’ll have a long time to wait before seeing any real savings.

Source: GM