Despite the fact that V-8s account for 35 percent of Jeep Grand Cherokee sales and 16 percent of five-door Ford Explorers, GM continues to resist equipping its mid-size-SUV lineup with the hot rodder’s (and trailer tower’s) engine of choice. Instead, the General is developing a lineup of in-line engines. These four-, five-, and six-cylinder motors will displace from 2.4 to 4.2 liters, they’ll share 75 to 80 percent of their parts, and they’ll be built on the same machinery — all of which slashes production costs.
First out of the shoot will be the Bravada’s all-aluminum DOHC 24-valve 4.2-liter six. It features variable valve timing, a separate coil on each plug to improve ignition accuracy, a throttle-by-wire system that integrates cruise- and traction-control functions, and a healthy 10.0:1 compression ratio (don’t fret, it runs on regular gas). Play a game of guess-that-engine, and someone hearing this description might mistake the Vortec 4200 for a BMW motor.
Efficiency and low emissions were high priorities in this design. Only the exhaust-valve cam timing is variable, within a range of 25 degrees of camshaft rotation. This permits precise tailoring of the amount of residual exhaust (and unburned hydrocarbons) that remains in the cylinder at varying speed and load conditions and negates the need for external exhaust-gas-recirculation plumbing. A close-coupled catalyst cleans up what little noxious fumes escape the cylinder, helping the Vortec 4200 meet National Low-Emission Vehicle (NLEV) standards without an air pump.
Horsepower and torque are guesstimated at just over 250 each. That would outpower the 4.9-liter Ford and 4.7-liter Jeep V-8s, while trailing on torque (as expected from a smaller, unboosted engine). We drove a prototype 4.2-liter Bravada and found it to be infinitely more responsive, refined, and quiet — not to mention quicker — than its 4.3-liter, 90-degree, V-6-powered forebear.
The real fire breather will be the 3.5-liter turbocharged five-banger scheduled for ’03 or ’04. With oil jets cooling the pistons and water cooling the turbo, that engine is expected to provide 4.8-liter V-8-like output (roughly 270 horsepower and 285 pound-feet) with eight percent better fuel economy. The fours and fives will be smoothed by balance shafts and other measures. Could it be that we don’t need another V-8 after all?
– Frank Markus