Magnetic Selective Ride Control gives the ZR1 a remarkable balance between ride comfort and responsive handling.
By Josh Jacquot, Senior Editor | Published Jul 13, 2010
Here's the thing about a car that produces 638 horsepower and 604 pound-feet of torque. These staggering numbers are superb ammunition for bench-racing, but reality tells us that of the few who can afford a $109,130 2010 Chevrolet Corvette ZR1, far fewer can actually drive this car anywhere near its potential.
Chevrolet knows this.
Even as forgiving as the Corvette ZR1 is when it comes to handling, it makes enough power to demand specialized, exacting attention to the use of its throttle. And that kind of attention is something that's often beyond the capability of the very people who find themselves piloting one of these latent liability cases.
It is this knowledge that has motivated Chevrolet to integrate many of the subsystems already in use within the 2010 Chevrolet Corvette ZR1 to create its new-for-2010 Performance Traction Management (PTM) system — an advanced, adjustable combination of chassis control systems designed to enhance the ZR1's performance in the hands of any driver.
What Is PTM?
Pushing this button twice activates PTM.
As an evolution of Chevrolet's "Competitive Driving Mode," PTM distinguishes itself from the stability control software of every other model of the Corvette with its ability to deliver five different settings of electronic management. They range from PTM1 — which is tuned for a wet track and employs heavy use of the car's active handling system (stability control) — to PTM5 — which disables the Active Handling system and allows use of all available torque (though it requires the car's Michelin Pilot Sport 2 tires to be up to temperature before it works properly). In between PTM1 and PTM5 are varying levels of power and stability management for varying levels of driving skill and experience.
Here's how it works. Once you push the stability control button twice, the PTM display comes up in the Driver Information Center (DIC). The Selective Ride knob then allows you to select one of the five PTM settings. Control of the Selective Ride system is then left to PTM, so there's no need to further choose between Tour or Sport modes. When activated, PTM manages the traction control, active handling (stability control) and launch control systems.
And it's stunningly good.
Using PTM
The Driver Information Center displays all five PTM settings.
Nowhere is the system's effectiveness more amply demonstrated than while driving the car through the same set of turns, much as you would at a track day. We experimented with various settings and finally settled on PTM5, which was the quickest in terms of elapsed time and provided the most confidence to the driver. After a period of building trust in the system, we found ourselves using wide-open throttle early and often while relying on PTM to keep the car on the road. Learning this technique is part trial and trust and part blind faith, but once you're accustomed to PTM's capabilities, the results are truly remarkable.
That it can best the European cars on a racetrack with an amateur at the wheel is just an added bonus.
Having reached the point in the corner where we would under normal circumstances begin to carefully squeeze the throttle, we simply mashed our foot to the carpet and let PTM do its business. The result was the telltale blat of an aggressive cut of the ignition that limited the massive output of the 2010 Chevrolet Corvette ZR1's supercharged engine, nevertheless accompanied by useful forward thrust. PTM won't drive for you, but it removes the risk in throttle control, which is the most demanding skill required to effectively drive a car this powerful. If the ZR1 was well mannered before, now it's downright domesticated.
With all PTM management turned off, the ZR1 is a wholly different beast, one capable of incredible speed accompanied by the persistent suspicion that things might end in a ball of fire. And it's not that this car is unmanageable. It's quite good, actually, when one considers the available power. But it's better with PTM.
Measure It
This knob controls the Magnetic Selective Ride Control but also switches between PTM settings.
PTM also proved itself in our slalom testing, where speed and driver confidence both took a substantial leap forward. We went a full 1.0 mph faster (72.8 mph vs. 71.8 mph) than with all electronic aids disabled. The rapid directional transitions required in the slalom are where PTM seems to do its best work. We say this because we were still able to beat the system on the skid pad, as lateral acceleration was better with PTM disabled, improving from 1.0g to 1.02g.
Straight-line testing using the ZR1's new launch control system also is impressive. In fact, PTM-based launch control is more advanced and effective than any of Chevrolet's previous launch control systems (think Camaro SS and Cobalt SS). Chevy's chassis engineers aren't quick to reveal details about the software's inner workings, but did admit that the system is using closed-loop feedback (probably by looking at the speed of front wheels vs. rear wheels and other data), which helps deliver the ability to dial in the power that goes to the ground in real time as it's happening.
Using PTM, the 2010 Chevrolet Corvette ZR1 hits 60 mph in 4.0 seconds (3.7 seconds using 1 foot of rollout like on a drag strip) and slams through the quarter-mile in 11.7 seconds at 127.0 mph. Once we switched off the PTM, our raw times were only 0.03 second quicker to 60 mph. When we corrected this data according to the weather and rounded to the nearest tenth of a second (as is our standard procedure), the time to 60 mph proved to be 3.9 seconds. With the corrections, the quarter-mile is essentially the same: 11.7 seconds at 126.7 mph.
This means that PTM is essentially as good as a driver who performs this test weekly on every car sold in the U.S. and has been doing so for 10 years. And in our book, that's pretty darned good.
Braking from 60 mph required 101 feet and came with the confidence one would expect of a brake system this advanced. In other words, it feels like it could operate at this load indefinitely.
(The above test data is marginally off the standard set by the 2009 Chevrolet Corvette ZR1 we last tested. That test, however, was performed on a different surface with better grip.)
http://www.youtube.com/watch?v=2uORyZI1VdU