General Motors introduced its 2002 midsize SUVs (Oldsmobile Bravada, GMC Envoy, and Chevrolet TrailBlazer) to the international automotive press in Los Cabos on the tip of the Mexican Baja peninsula. We were able to clock about 100 miles of driving on rough and fast Mexican two-lanes-flat and climbing, straight and twisting-and a few laps around an off-road course with steep climbs and descents and 50-mph washboards.Mostly, we were dazzled by the Vortec 4200 engine. The new Vortec 4200 engine is highly sophisticated: an all-aluminum, double-overhead-cam, 24-valve inline six-not a V8. If a straight-six engine is good enough for BMW and Lexus sedans, why not an Oldsmobile truck? From 4.2 liters, it produces a stunning 270 horsepower, 35 more than the Jeep and 30 more than an Infiniti QX4, Acura MDX or Nissan Pathfinder. It incorporates state-of-the-art engine construction and electronic management, and yields an estimated fuel mileage of about 15/21 mpg city/highway.
It features variable valve timing, electronic throttle control, coil-on-plug ignition and a seven-quart oil pan with a clever tunnel for the front drive axle, which allows the longish block to be mounted six inches lower, contributing to better balance and a lower center of gravity. It's so quiet and smooth at idle that a feature called intellistart" had to be added to prevent drivers (initially GM test drivers and engineers) from grinding the starter by turning the key when the engine is already running. And the faster it goes, the smoother it gets. With an official Mexican Highway Patrol escort along on the test drive, we felt free to squirt up to 100 mph, and found much to our pleasure how silky the inline engine is at 80 and above.
The engine also has a very broad torque curve; 90 percent of its peak 275 pounds-feet is available at 1600 rpm, and it's still there at 5600 rpm. This enabled us to leap past Mexican trucks on steep uphill two-lanes with confidence, while allowing the transmission to do dramatically less downshifting. And when the full-throttle upshift comes at about 6000 rpm the engine is only striding, not screaming. The smooth-shifting four-speed automatic transmission is the proven Hydra-matic 4L60-E, used in GM applications from Corvettes to Cadillac Escalades. Our test model was equipped with the standard 3.73:1 rear end differential, with a 4.10 for more oomph in towing.
The load leveling suspension uses electronically controlled air bladders fitted to the rear coil springs. It's intended to improve the ride while dealing with off-road nearly as well as the rugged coils. Road inputs are monitored by sensors that tell the system to inflate and deflate the bladders independently, leveling the load horizontally as well as vertically. Because the system uses a small (silent) air compressor, there's a standard 22-foot-long hose which when attached to a valve in the cargo area can inflate anything from tires to toys.
We drove the Bravada back-to-back with the TrailBlazer, having the same chassis and suspension but without the air springs, and could clearly see the difference--especially over speed bumps (and those topes are ubiquitous in Mexico). Surprisingly, we found that the air suspension didn't significantly hamper high-speed cornering. And GM engineers at the introduction revealed that there is even an internal debate among them, about how much if any this tilt toward luxury handicaps the Bravada in the hard twisties.
The chassis and suspension are also highly developed, with components that might be found on a high-performance sedan: hydraulically assisted rack-and-pinion steering, four-wheel vented anti-lock disc brakes with twin-piston calipers in front, independent front suspension, five-link rear suspension with Bilstein shock absorbers, and that sophisticated air-bladder mechanism on the rear coil springs for a smoother ride.
The chassis rails are shaped by hydroforming, a process that makes them stronger and lighter. No fewer than eight crossmembers contribute to a claimed 260-percent increase in torsional rigidity, and there are 12 tuned body mounts designed to reduce noise and vibration.
The brakes work really well. Under hard braking, the Bravada remained level and stable. The front rotors are 12.0 inches and the rears 12.8, with a total swept area of 424 square inches. In addition, the aluminum front calipers are twin-piston. However the rotors seem to be susceptible to catching debris, especially off-road. But it's a problem that might already have been fixed by engineers in the two months between this introduction and vehicle production at its plant in Moraine, Ohio.
The Bravada isn't expected to be thrashed off-road-the TrailBlazer is the one for that-but it can be. It's got all the same stuff as the TrailBlazer, and again, the air suspension is no great handicap. We drove it over the same offroad course, at the same high speed over washboard surfaces, and found the rear end stayed planted extremely well. The SmartTrak all-wheel-drive system lacks the low-range 4WD of the TrailBlazer, but Bravada owners are unlikely to ever get in that deep."
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