Seemingly every other week, there is an announcement about a new CNG-compatible model coming. Among the full-size truck segment, there are now fairly plentiful offerings. The Ford F-150 and Super Duty models offer a bi-fuel CNG package, and the 2014 Ford Transit Connect and full-size Transit have CNG/LPG upfit packages. Ram has a bi-fuel 2500 HD model, and GM just today announced the availability of CNG bi-fuel versions of its 2015 HD trucks and dedicated CNG versions of its 2014 Chevrolet Express and GMC Savana full-size vans.
This relative abundance of CNG options is a laudable and massive improvement over the scarce options of a few years ago, some of which were aftermarket conversions that didn't come with a full factory warranty. All these vehicles are still primarily focused and targeted toward the fleet buyer. There's logic to this approach, as fleets interested in buying CNG vehicles often have private fueling facilities, and the vehicles go on fixed routes, where there's predictability in terms of range and fuel consumption.
Other than these trucks and vans, only one CNG vehicle currently on the market could be considered a "consumer" vehicle, the Honda Civic Natural Gas. Honda has offered the Civic with a CNG option for more than 15 years now, and its earlier iterations were clearly targeted to fleet buyers, with a bare-bones features selection, and a measly two-speaker sound system. Navigation and upgraded audio systems were not an option. Only with the introduction of the latest version were any significant concessions made to comfort and convenience amenities.
The decision for OEs to tiptoe into the CNG market with bi-fuel models that can run on gasoline or CNG is understandable, since availability of high-pressure public CNG filling stations is spotty at best on the national level. Southern California happens to have one of the highest concentrations of publicly accessible CNG filling stations in the U.S., so "range anxiety" for regular CNG users is not a huge issue if they do some basic self-education on scouting out filling locations. However, there are some other states with only a small handful of public CNG stations, or none at all, and some spread hundreds of miles apart. For those markets, dedicated CNG vehicles don’t make much sense.
The inherent problem with bi-fuel vehicles is that they're a compromise for convenience. CNG, although squeaky-clean from an emissions standpoint, has a lower BTU value than an equivalent amount of gasoline. Bi-fuel engines have compression ratios and valve timing optimized for gasoline, so power output takes an inevitable hit when running on CNG. Interestingly, none of the bi-fuel or CNG models currently offered from the factory have a turbocharger, the one item that could largely mitigate the power loss with CNG. But there is precedent elsewhere in the world for optimized performance. Fiat sells a significant number of vehicles in its home market of Europe under the Natural Power brand. The 1.4-liter Fire T-Jet bi-fuel engine produces 120 hp running on either gasoline or CNG, thanks to turbocharging. Such an engine seems like it could be a great choice for the upcoming ProMaster City (the U.S.-market version of the Fiat Doblo small van).
If you were to give up gasoline compatibility altogether, you could bump the compression ratio on naturally aspirated engines to better harness the lower BTU value of CNG, or bump the boost and compression on a dedicated CNG turbo. It would also allow for more optimized packaging of fuel storage, and possibly get rid of the cargo-robbing bed-mounted tanks in pickups, with fully chassis-mounted CNG tanks.
And although there has been plenty of discussion and controversy on the merits or liabilities of "fracking," there are other ways to harvest methane, the primary component of natural gas. It's been proven it can be scavenged from landfills and sewage treatment plants, two things the world, and especially the consumer-driven U.S., is unlikely to run out of anytime soon. Sure, the prospect of sitting on top of pressurized 3600-psi tanks of flammable gas freaks a lot of people out, but several studies have shown the safety of CNG to be equivalent to or better than that of gasoline, a fuel people have been living with largely without incident for more than a century.
Living in an area with about 10 CNG filling stations within a 10-mile radius of my house, I'd be willing to give up the bi-fuel safety net to get some optimized performance and packaging from a CNG vehicle. Like the initial roll out of plug-in hybrids or EVs, perhaps offer these models first in regions with relatively abundant availability of public CNG stations, and roll them out to broader markets as the fueling infrastructure expands. What do you say? Are you ready for a purpose-built CNG vehicle?