Honda’s Rodney Dangerfield of Alt-Fuel Vehicles

With all the excitement about electric vehicles these days, the natural gas Honda Civic GX just doesn’t get any respect. Perhaps that’s because it still burns fossil fuel in an internal combustion engine, which may seem to some like incremental innovation. But a closer look at the car, which debuted in 1998 and has sold several thousand since then, reveals an interesting story about the cleanest internal combustion vehicle in the United States.

The Civic GX program was born of an era when the enemy was smog emissions and air quality, not global warming.


“At the time, we were considering the ZEV mandate,” Steve Ellis, Honda’s manager for alternative fuels sales and marketing, said, referring to the California Air Resources Board mandate that large manufacturers produce a certain number of zero-emissions vehicles. “The goal was originally clean air, so Honda engineers set out to use the cleanest fuel – natural gas.”

The cleanest of the alt fuels.

The program was launched alongside the EV Plus, Honda’s contribution to the first wave of modern production electric vehicles spurred by California regulators in the 1990s. Honda leased about 300 EV Plus cars from 1997 to 1999 but ended the program shortly thereafter in favor of more extensive development of its hydrogen fuel cell program.

It is fairly easy and cheap to convert internal combustion engines to run on natural gas, but the results of a simple conversion are not very good. While the internals of an engine running on natural gas are very similar to those of a gasoline engine, the natural gas engine must run at a much higher compression ratio to generate the same power as a gasoline engine. These days a typical gas engine runs at a compression ratio of about 9 to 1. A high performance car might run at 10.5 to 1. Generally speaking, the higher the compression ratio the more power an engine can produce, but above a certain ratio gasoline will prematurely and spontaneously ignite in the chamber, which is something to avoid. The higher the octane rating of the fuel, the more it can tolerate high levels of compression.

Natural gas has a very high octane rating, so Honda engineered an engine with a 12.5 to 1 compression ratio, allowing it to produce roughly the same output as a similarly sized gasoline engine. To run that high, the internal components of the engine read like a spec sheet from an import tuner magazine: forged pistons, modified valve seats, modified crank journals and a forged crankshaft. Even with these mods, the 1.8 liter Civic GX engine produces only 113 horsepower compared to 140 for the standard gas powered 1.8 liter. Perhaps Honda should bump the compression to 15 to 1.

The fuel delivery system is completely different, since it is delivering compressed gas from a 3,600 psi “tank” to the fuel rail at 40 psi instead of delivering liquid gasoline to the injectors. The catalytic converter also is different, having been optimized for natural gas combustion. As a result Honda claims smog emissions from the Civic GX are so low as to be immeasurable. The GX is the cleanest internal combustion car in America.

An engine a hot rodder could love.

But the environmental debate about cars has moved on from the old enemies of nitrous oxides and carbon monoxides. Part of the reason is manufacturers have made internal combustion engines so “clean” with respect to smog emissions that customers can no longer kill themselves leaving the engine running in a closed garage. The other reason is carbon dioxide, the friendly gas of soda pop and champagne and the same gas we exhale with every breath, has emerged as public enemy number one, surely dooming our civilization to mass extinction if we don’t act before the next election cycle.


Then what will become of the Civic GX, which starts at $25,340? There is no way around the fact that when you burn a hydrocarbon you create carbon dioxide. Even though natural gas is the least carbon intensive of fuels, with just one carbon atom to four hydrogen atoms, it saves only 25 percent on CO2 emissions per mile when compared to a comparable gas powered car, according to Honda.

So the Civic GX may get no respect from the global warming crowd, but there are still reasons to support natural gas as a viable alternative to gasoline. While the carbon footprint per mile doesn’t compare favorably to an electric drivetrain, the fuel being burned is almost entirely domestically sourced, with about 2 percent of domestic natural gas being imported from other countries. Since natural gas is a viable alternative across all types of vehicles in the fleet, from small cars like the Civic GX to large cargo haulers, the ability to displace foreign sourced gasoline miles with domestically sourced natural gas miles is very attractive to those whose motivation to get off gas is more closely tied to energy independence and foreign policy. Last but certainly not least, natural gas has been consistently cheaper than gasoline for the past decade by about 50 cents to a dollar per “gasoline gallon equivalent,” and natural gas cars avoid the significant expense of batteries.


Even optimistic projections of electric vehicle adoption still have internal combustion vehicles as the dominant form of transportation for many decades to come, so driving a shift from gasoline to natural gas is a smart goal to pursue in parallel with the electrification of our vehicle fleet.

Photos: Honda

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