GMC debuts smaller model

  • 16-Apr-2009 08:16 EDT
The GMC Terrain represents a combination of GMC luxury with modern customer demands for fuel economy, with a direct-injected 2.4-L I4 engine achieving an expected 30 mpg on the EPA's highway fuel economy test.

General Motors expanded its family of compact crossover SUVs built on the corporate Theta platform with the announcement of the GMC Terrain, a derivative that is styled to look more like the traditional body-on-frame trucks that comprise most of GMC’s portfolio.

Like other GMC models, the Terrain is available with an impressive array of standard and optional features, such as a standard rear backup camera, a programmable power liftgate, remote vehicle start, and an infotainment/navigation system that includes a 7-in touch screen, USB input, MP3 playback, 40-GB hard drive, and DVD rear entertainment with two display screens.

The cabin is styled to match GMC’s aspiration to be recognized as a luxury brand, with premium leather upholstery and warm ambient lighting. But even more important in this segment is practicality, and the Terrain features an adjustable rear seat GM brands MultiFlex. The MultiFlex seat slides fore-and-aft 200 mm (7.9 in) and has a 60/40 split seat back for the ability to accommodate passengers, cargo, or both. Front-seat storage includes the glove box, closed storage in the middle of the dashboard, and a center console large enough to contain a laptop computer.

The Terrain features two of GM’s latest direct-injected engines, a 2.4-L Ecotec I4 and 3.0-L V6.  Both engines will be widely shared throughout the GM lineup, and the company said that 90% of its engines will be direct injected within a few years.

The Ecotec is rated at 182 hp (136 kW) and 174 lb·ft (236 N·m), providing a slight power increase over the most powerful port-injected version of the engine, which was rated at 173 hp (129 kW) and 170 lb·ft (230 N·m), said Amy Joss, assistant chief engineer for the Ecotec engine.

Noise was a particular challenge for direct injected engines because of the high pressure in the fuel-injection system, and GM engineers worked hard to address that problem in the Terrain, Joss said.

“We worked extensively with [fuel-injection system] supplier Hitachi to make sure we have noise as minimized as possible,” she explained. “You send high pressure through a line; if you don’t have it isolated correctly and don’t have the design of the fuel rail just right, you get some noise.”

To suppress any noise that is generated, the fuel pump wears an acoustic cover, and the I4 Terrain further employs an active noise cancellation system using the stereo’s speakers in the cabin.

The V6, rated at 264 hp (197 kW) and 222 lb·ft (301 N·m), boasts an “inverted tooth” cam chain design that provides the maintenance-free durability of chain drive without the typical noise. The design prolongs the period of contact between the sprocket and the chain for smoother, quieter operation, according to the company.

Thanks to their direct-injection systems, both engines exploit high compression ratios for maximum efficiency, with 11.4:1 for the I4 and 11.7:1 for the V6.

Both engines mate to six-speed automatic transmissions and are available with either front- or all-wheel-drive.

Expected EPA fuel economy is 21 mpg city, 30 mpg highway for the FWD I4 model and 20/27 mpg for the AWD model. The V6 scores 18/25 mpg in FWD form and one mpg lower on both tests for the AWD version.

Achieving 30 mpg was a top priority for the program, said Joss. That was accomplished in part through the use of an “eco” button on the Terrain’s console which lowers the torque converter’s lockup speed to 1250 rpm. The improved fuel control with the direct injection system was worth about a 1% improvement in efficiency, according to Joss, and the one point increase in compression ratio was worth another 1% in fuel efficiency, she added.

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