Thursday, June 23, 2011
This is where we venture beyond customary performance tests to decipher two of car enthusiasm’s enduring mysteries: Does spotting the engine in the optimum location—in the middle of the car—yield demonstrably better handling? And can engineering theory trounce painstaking practice?
Porsche’s 2012 Cayman R, the hottest mid-engined model in Porsche’s current lineup, represents the theory side of the equation. This is the thinking man’s sports car—light, stripped, and hunkered down for utmost agility. Aluminum door skins, a bare-bones interior, carbon-fiber seat structures, and new 19-inch wheels hold the curb weight to 3076 pounds. Air conditioning and audio-entertainment equipment are optional. Porsche’s 3.4-liter, direct-injection flat-six has been goaded to 330 horsepower at 7400 rpm, a 10-hp gain over the standard Cayman S. While price doesn’t count in this analysis, the Cayman R starts at $67,250, a pocket-warming $12,700 less than a base 911.
We tapped a 911 GT3—the proud son in an unbroken line of rear-engined Porsches dating back to 1948—to represent the practice-makes-perfect argument. What the GT3 lacks in value (as-tested price: $130,910), it overcomes with pure grit. In terms of power-to-weight ratio, this is the second-hottest naturally aspirated Porsche money can buy (after the GT3 RS). The 435-hp, 3.8-liter flat-six and the six-speed transaxle powering this 911 descend from battle-hardened race hardware. Prepped GT3s compete in the Porsche Supercup, a Formula 1 support series. Decades of exorcising handling gremlins that come with hanging a 570-pound engine behind the rear axle have paid off in razor-edged reflexes. The latest fix is a $1300 set of dynamic engine mounts that cinch up during aggressive maneuvers to calm the GT3’s transient behavior.
We tapped a 911 GT3—the proud son in an unbroken line of rear-engined Porsches dating back to 1948—to represent the practice-makes-perfect argument. What the GT3 lacks in value (as-tested price: $130,910), it overcomes with pure grit. In terms of power-to-weight ratio, this is the second-hottest naturally aspirated Porsche money can buy (after the GT3 RS). The 435-hp, 3.8-liter flat-six and the six-speed transaxle powering this 911 descend from battle-hardened race hardware. Prepped GT3s compete in the Porsche Supercup, a Formula 1 support series. Decades of exorcising handling gremlins that come with hanging a 570-pound engine behind the rear axle have paid off in razor-edged reflexes. The latest fix is a $1300 set of dynamic engine mounts that cinch up during aggressive maneuvers to calm the GT3’s transient behavior.
These road warriors are the ultimate examples of their respective 987/997 breeds. A seventh-generation 911, which will beget a new, third-generation Boxster/Cayman, is scheduled to bow at this fall’s Frankfurt auto show. To compile the evidence that would convincingly prove which engine location works better, we dug deeply into our box of tools.
Cayman Dynamics, a team of vehicle-dynamics experts on call to support our more ambitious tests, cracked the door to a local laboratory where a million-dollar test rig measured each Porsche’s center-of-gravity height and polar moment of inertia [see “Engine-Location Glossary”].
Supplementing the normal acceleration, braking, and cornering tests, we lapped the Chrysler Proving Grounds road circuit where the Dodge Viper’s fangs were sharpened. All our tests were run with stability control disabled.
To measure agility and predictability at the ragged edge of adhesion, we reconfigured the classic slalom test and cooked up a new step-steering-input maneuver.
To monitor yaw rate and slip angle throughout our tests, we used a dual-antenna Racelogic VBOX II SXSL3 data logger.
Source : http://www.caranddriver.com/
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