The turbocharged and intercooled 2.8-liter V-6 is both the baby of GM's 'high-feature' V-6 engine family and a hand-me-down from the Saab 9-3 and Opel Insignia. Notable features are an aluminum block with a shorter stroke than the SRX's 3.0-liter normally aspirated engine, cast-iron cylinder liners, jets that spray oil on the bottom side of the cast pistons, a forged steel crankshaft and connecting rods, and cross-bolted main bearings. Up top, there's a large air-to-air intercooler; intake and exhaust cams are both equipped with variable valve timing. The twin-scroll Mitsubishi turbo delivers a maximum 10.5 psi of boost which is present and accounted for by 2000 rpm after a jab of the throttle. The dead-flat 295 lb-ft torque plateau holds steadily to 5000 rpm and this engine continues revving enthusiastically to its 6200 rpm redline. Premium fuel is required. Since this Australian-assembled V-6 has been in service for four years, it doesn't benefit from the latest direct fuel injection technology.
The 6-speed automatic transmission is the reason why the torque is never allowed to rise about 295 lb-ft. Supplied by Aisin (in contrast to the 6-speed HydraMatic teamed with the 3.0-liter V-6), this box provides four modes-regular automatic shifting, an eco mode with early gear change programming, a Sport mode calibrated for aggressive drivers, and full manual operation with shifts controlled by the console lever. Ordering up the last two modes also tightens the dampers and firms the steering.
A Haldex coupling routes torque to the rear wheels on demand and when commanded to do so by a powertrain control computer. That device also regulates the operation of the electronically controlled limited slip rear differential. In the event one rear wheel spins on low-traction surfaces, the wheel on the opposite side quickly picks up the slack to maintain momentum.
SMART CHASSIS SYSTEMS
The ZF Servotronic speed-sensitive hydraulic power steering, Sachs continuously variable dampers, reasonably sized floating-caliper disc brakes, and a transmission that responds to the driver's preferences are all top-shelf technologies. The new turbocharged engine clips a second off the 3.0-liter V-6's zero-to-sixty acceleration time but that run still requires 7.5 seconds according to Cadillac. What keeps the SRX from demonstrating seriously sporting speed is its 4500-pound curb weight and the fact that the front wheels carry more than 56-percent of that load.
So the ride is well controlled and able to take bumps in stride but there's too little body control for hard driving. The Michelin Latitude Tour HP radials, size 235/55HR-20, give up the ghost when pressed resulting in ponderous understeer. The Haldex system needs to be recalibrated to shift more of the propulsion responsibility to the rear wheels during dry-road sprints.
Another issue is the bucket seats' design. There's too little lateral support in both the backrest and the bottom cushions to restrain the driver during hard cornering.