Driving on Gas

Bi-fuel Ford conversion runs on both gasoline and CNG – but is it right for your operation?

By Steve Temple

Contractors and fleet managers feel pain at the pump more than most pickup owners, since one of their biggest overhead expenses is fuel.

No surprise, then, many are considering a variety of mileage extenders, using everything from computer tuning modules to fuel additives to alternative fuels.

We’ve been checking out one in particular, Compressed Natural Gas (CNG), after spotting several bi-fuel pickup conversions at this year’s NTEA Work Truck Show.

In addition to already taking a hard-nosed looked at the financial pros and cons of CNG (see Money Matters in our June 2012 issue), we wanted to check out one on the road for a hands-on driving experience.

So we turned to Venchurs Vehicle Systems (VVS) to get seat time in a 2012 F-250 running a dual-fuel 6.2L.

DRIVING CNG

Bi-fuel CNG tanks are big and take up bed space. This one does
have a small amount of storage above the tank inside the enclosure.

The VVS conversion has the ability to operate on two separate fuel supplies, injecting either gasoline or compressed natural gas with the simple flip of a dash-mounted rocker as you drive.

The transition between the two fuels is seamless, with no obvious changes in performance.

Venchurs system ports CNG directly into the cylinder, and by optimizing the tune and air/fuel ratio, using CNG loses only three percent in power, which is said to be within the five percent variance found in manufacturers’ OEM engine ratings.

Clean Energy, a key supplier in the natural gas market, says a CNG-only engine would normally provide the same power output, but noted it’s difficult to optimize an engine for dual fuels, suggesting one possible reason for the slightly lowered output of the Bi-fuel application.

Even so, the VVS conversion does not significantly affect cargo hauling or tow ratings, and the fuel economy is claimed to be 11 mpg in the city and 14 mpg on the highway.

In gasoline mode, the dash readout indicated 15 mpg on the highway at 65 mpg (Ford does not publish fuel economy ratings on this size of truck). Also, the truck’s onboard computer does not provide fuel consumption data when running in CNG mode, so we used the traditional method of counting miles and volume consumed to verify Venchurs’ mileage claims.

Even though the observed fuel economy is about a mile-per-gallon less with CNG (in an engine with a dual-fuel capability), it can dramatically reduce fuel costs, since the price of CNG runs $1.25 to $2 less on a per gasoline gallon equivalent (GGE) basis.

There’s an even greater fuel savings compared to the cost per gallon of diesel. But keep in mind diesel has a higher energy rating of 129,488 Btu/Unit, while CNG’s is 98,300 Btu/Unit, according to the Department of Energy.

So no surprise that the ­horsepower and torque outputs on the slightly larger 6.7L Power Stroke are significantly higher than gasoline (400hp vs 385, and 800 lb/ft vs 405).

Another point in favor of a VVS conversion (available on the 6.2L F-350 as well) includes its designation as a “Ford Qualified Vehicle Modifier.” That means VVS conversion won’t void the factory warranty and can be rolled into Ford financing programs.