Total Landscape Care Digital Magazine
Issue link: http://read.dmtmag.com/i/356210
ProPickup engineers could optimize the driving characteristics of the two different fuels. The CNG module has a dif- ferent engine and transmission calibrations than the module on the gasoline side: Injector dura- tions and flow, engine timing, transmission shift points and a host of other calibrations have been changed to meet stringent EPA emissions goals. Driving the 2500HD on CNG is no different than when regular 89-octane E-10 flows through the 6.0L's injectors: The engine is smooth, and the exhaust quiet. Where I feel the difference between running on gas and CNG is when you really lay the throttle down. That's when the power difference between the fuels is readily apparent. The GM 6.0L V8 makes a respectable 360 horsepower on gasoline but drops 59 of those horses when CNG runs through it. GM CNG engineer Mike Jones says the drop in power is a result of tuning the engine so it meets EPA requirements. Although the BTU of CNG is closer to that of diesel than E-10 unleaded, Jones says the current engine technology in the way the gaseous fuel is delivered doesn't take full advantage of that energy. "When we first began experi- menting with CNG engines, they made better horsepower and fuel economy than they did running on gas," notes Jones, reflecting back several years. "But we have to meet certain emissions criteria and that has an adverse affect on both power and mpg with our current technology." Comparing MPG Consequently, when the CNG switch is activated, the Silverado takes a 20-percent hit in both horsepower and fuel economy as the trade-off for running an environmentally clean fuel. I saw 15.1 mpg running the truck on E-10 gasoline on the 108-mile round-trip stretch of relatively flat I-10 I use for testing fuel economy between Gulfport, Mississippi, and Pasca- goula, Mississippi. The run is at a steady 70 mph. Switching over to CNG, the fuel bar and the percentage readout above it showed 45 percent left in the tank at the end of the same round-trip test. That's the equivalent of 11.6 mpg. At that rate, the range on the 17GGE CNG tank should be almost 200 miles. But that's not how CNG works. In today's CNG vehicles, the capacity on the tank is not the useable capacity: The useable capacity is about 2/3 of the tank's rating, or in this instance, 12 GGE with a driving range of about 140 miles. 5 0 To t a l L a n d s c a p e C a r e . c o m A U G U S T 2 014 LT's cloth seats, with the optional MyLiink audio/navi system, makes for a comfortable work truck. Part of the $435 "Cargo Convenience" option package is this under-seat rear storage compartment.