Perverse Polarity: Is Porsche Ready to do Right by the Cayman?
Tuesday, August 9, 2011 by admin
I’ve never wanted to own a Porsche 911, though they are great fun to drive. They’re even wilder to ride in with a pro like Walter Rohrl flailing away at the helm. Such rides sometimes make me wonder if the “laws of physics” are open to creative interpretation like our Constitution. But two mechanical engineering degrees tell me they’re not, hence, in my mind no proper racebred chassis should have its engine cantilevered off the rear axle (or the front). Yes, the 911′s setup loads the rear tires for better launch acceleration and provides slightly better weight distribution under hard braking, but if this arrangement is superior, why doesn’t anybody else in racing use it? I’m willing to bet that a mid-engine Cayman could spank a 911 on the Nürburgring if equipped with equivalent power, tires, and chassis optimization. So is it just pig-headed German stubbornness keeping the Cayman down?
I’ve put that question (more politely) to numerous Porsche engineers throughout the years, and they all shrug it off with dubious assertions about insufficient chassis rigidity, cooling challenges, etc. Really? C’mon. Surely the minds that tamed the once-feral 911 Turbo would make quick work of those challenges.
The obscure physics law that favors the Cayman is its polar moment of inertia. You know inertia means resistance to change (a key tenet of 911 product planning), only here the change is rotation about “poles” drawn through the vehicle’s center of gravity. The important one for handling is the car’s moment of inertia about the vertical axis when it yaws (turns or spins). High-polar-moment cars resist turning in or spinning; low-moment cars turn in more eagerly. To visualize the difference, run up to the attic and grab your old turntable and a curling dumbbell. Set the dumbbell on the Close’N Play platter with one weight on either side (high moment) and try spinning it. Now stack the weights on top of each other centered on the spindle (negligible moment). Spins way easier, right? The Cayman’s polar moment is said to be 20 percent lower than the 911′s.
Porsche may be unwilling to build a high-output Cayman, but Ruf GmbH has done the job, so I borrowed a 2007 Ruf 3400K from Ruf Auto U.S. It started life as a Porsche Cayman bodyshell, upfitted with a supercharged, intercooled 3.4-liter flat-6 rated at 400 horses and 324 pound-feet of torque, beefier brakes, a starchier lowered suspension, and 19-inch Pilot Sport tires. I was amazed at how nimble and lively the car feels, biting eagerly into turns, delivering all the same delightful steering feedback with an almost Lotus-like delicacy in the way it handles. There’s never the sense that gigantic rear tires are levering a massive engine around an apex in this car. This makes its limits seem more approachable by mere mortals, which, as you’ll read next month, is a key attribute of the very best driver’s cars. By contrast, super-911s give the impression that breaching their amazingly high limits would be catastrophic.
With the 2012 911 growing to provide more rear seat space, and a mid-engine VW-based baby Boxster on the way, might Porsche be ready to transition the 911 to GT duty and develop the Cayman into the proper racebred sports car it’s always longed to be? Here’s hoping-and make mine a turbocharged GT2 RS.
The obscure physics law that favors the Cayman is its polar moment of inertia. You know inertia means resistance to change (a key tenet of 911 product planning), only here the change is rotation about “poles” drawn through the vehicle’s center of gravity. The important one for handling is the car’s moment of inertia about the vertical axis when it yaws (turns or spins). High-polar-moment cars resist turning in or spinning; low-moment cars turn in more eagerly. To visualize the difference, run up to the attic and grab your old turntable and a curling dumbbell. Set the dumbbell on the Close’N Play platter with one weight on either side (high moment) and try spinning it. Now stack the weights on top of each other centered on the spindle (negligible moment). Spins way easier, right? The Cayman’s polar moment is said to be 20 percent lower than the 911′s.
Porsche may be unwilling to build a high-output Cayman, but Ruf GmbH has done the job, so I borrowed a 2007 Ruf 3400K from Ruf Auto U.S. It started life as a Porsche Cayman bodyshell, upfitted with a supercharged, intercooled 3.4-liter flat-6 rated at 400 horses and 324 pound-feet of torque, beefier brakes, a starchier lowered suspension, and 19-inch Pilot Sport tires. I was amazed at how nimble and lively the car feels, biting eagerly into turns, delivering all the same delightful steering feedback with an almost Lotus-like delicacy in the way it handles. There’s never the sense that gigantic rear tires are levering a massive engine around an apex in this car. This makes its limits seem more approachable by mere mortals, which, as you’ll read next month, is a key attribute of the very best driver’s cars. By contrast, super-911s give the impression that breaching their amazingly high limits would be catastrophic.
With the 2012 911 growing to provide more rear seat space, and a mid-engine VW-based baby Boxster on the way, might Porsche be ready to transition the 911 to GT duty and develop the Cayman into the proper racebred sports car it’s always longed to be? Here’s hoping-and make mine a turbocharged GT2 RS.
