Personality Test

Is the Grand Sport Z07 a thinly veiled racecar, a steroidally enhanced Stingray for the street or something else entirely? We dispatch contributor Eric Gustafson on a grueling, two-part test drive to find out

Personality Test 1
September 22, 2017

We left San Francisco at 4:30 a.m. We’d signed up for a Hooked on Driving track day at Thunderhill Raceway Park 150 miles to the north, and the driver’s meeting started at 7:30. Our aim was to simulate an ideal day in the life of a C7 Grand Sport owner, one that included open roads, a closed race course and lots of driving. It seemed the best way to test our 2017 Chevrolet press car. We quickly learned that San Francisco, with its narrow, bumpy streets and near-constant fog-induced drizzle, is not the Grand Sport’s preferred habitat, especially when it has been fitted with the Z07 Ultimate Performance Package ($7,995). Thanks to its stiffer springs and semi-slick, track-ready tires, the Grand Sport sent our heads jostling from side to side and the traction-control light flashing. The need to make a U-turn revealed a laughably wide turning radius and cringe-producing tire rub. This seven-speed manual’s decidedly useful hill-assist feature was not enough to make up for its other urban shortcomings. After picking up photographer David Bush, we were happy to get this yellow-and-black beast out of Dodge.

It was still dark as we crossed the Golden Gate Bridge and headed north on Highway 101. With the sharp report of the smooth-revving LT1 V-8 still echoing off its walls, we emerged from the Robin Williams Memorial Tunnel full of excitement. Freed from the clutches of the city, we were taking the Grand Sport to a place where we were confident its virtues would reveal themselves, where its advanced engineering would shine—not just the racetrack, but great Northern California back roads. Yet even just being on the freeway was a big improvement: With the Driver Mode Selector knob in Tour mode, the Grand Sport’s ride quality approached a level of civility its poor inner-city behavior would not have suggested. Its ability to soak up the potholes created by California’s record winter rains surprised us. And with the engine hardly loafing in Seventh gear at 70 miles an hour, the Grand Sport’s cockpit is admirably quiet. Only the thrum of its steamroller tires (the rears are a whopping 335mm wide) and their occasional tramlining divulged this model’s track-oriented demeanor. The optional Competition Sport Seats ($2,495), though optimized for support, proved long-haul comfortable. As our drive came just two days after the Summer Solstice, first light was quick to appear on the eastern horizon, illuminating golden foothills in the distance and subtly hinting at the day’s forthcoming heat. We were, after all, heading into California’s Central Valley, which is not only the state’s bread basket, but its oven. The forecast for Willows, home of Thunderhill, called for a high of 106.

Thunderstruck

Personality Test 2

We made it in time for the driver’s meeting, though we had to hustle to get the Grand Sport ready for the first track session—affixing stickers, removing gear and hurriedly attempting to learn the new track layout. We’d driven Thunderhill on numerous occasions, but not since the addition of the West Circuit, which, when combined with the existing East Circuit, makes for a lengthy five-mile lap. Feeling a bit nervous, we decided to begin the first session with the Driver Mode Selector in Sport. We wanted plenty of electronic assistance while we learned the track. With its numerous tight corners, two blind crests and a nasty off-camber bend, the West Circuit is challenging. But the Grand Sport immediately proved a confidence-inspiring dance partner, thanks to its surfeit of grip, neutral handling and sophisticated driver-aid systems. While the LT1’s 460-horsepower output was enough to get us up to speed in a hurry, it wasn’t enough to make us afraid of inadvertently grabbing too much throttle. A C7 Z06, with its 650 horses, would have been far more daunting given our place on the learning curve.

After a couple of laps, however, we were ready to sharpen the Corvette’s responses and switched the Driver Mode Selector into Track. We wanted both less body roll and less electronic intervention. What we didn’t want was the steering wheel to suddenly become ponderously heavy, but that’s what we got. Other aspects of Track mode weren’t to our liking, either. Though the damping was noticeably firmer, the amount of driver and traction control seemed hardly diminished. We experienced too much intervention in a few corners, such as 3E, which, not unlike Laguna Seca’s infamous Corkscrew, involves a rapid drop after cresting a hill. We wanted power to help rotate the car; the computer wasn’t giving it to us, preferring to wait until the rear end was fully weighted.

When we came into the pits at the end of that first 20-minute session, our priority was to better calibrate the Grand Sport’s numerous settings. While it’s easy to bemoan its complexity, we couldn’t help but be impressed by the sheer adjustability of this machine. Thankfully, we figured out how to independently set the steering in its lighter-weighted Sport mode. Then, we went into Performance Track Management and selected Sport 1, the midpoint of five available levels of intervention. This mode still allows for some driver aid while giving traction control a fairly long leash. The Sport 2 and Race modes deactivate Stabilitrak completely. With that, we eagerly awaited our second track session—and watched the thermometer readout creep upward.

Personality Test 3

By 10 a.m., the ambient temperature had already climbed into the 90s. The C7 doesn’t have a perfect record when it comes to cooling issues on track. Automatic-equipped Stingrays have been known to overheat during high-performance driving events, and the same issue became enough of a problem on the C7 Z06 (both automatic and manual versions) that Chevrolet made some mid-cycle changes on 2017 models. While there was no reason to question the cooling system of our clutch-pedal-equipped Grand Sport, it would nevertheless be put to the test on this day. So would the brakes. The Brembos included in the Z07 package had performed admirably thus far, proving squeal-free and reassuringly powerful. The immediacy of the brake pedal is a bit startling at first, but we quickly adapted and actually came to find it surprisingly progressive. With massive cross-drilled, carbon-ceramic rotors (measuring 15.5 inches up front, 15.3 in the rear), huge six-piston calipers and trick alloy hats, the brakes look like they came straight off a Le Mans prototype.

Adding to this Grand Sport’s racy appearance are the various aerodynamic aids included in the Z07 package, including a deep front splitter, wide side skirts and a larger rear spoiler, as well as special scoops over the rear fender-top ducts that direct more air into the differential and oil coolers. This is on top of the Grand Sport’s already enhanced silhouette; its wider Z06 hips are needed to cover up all that rear rubber. Thanks to their significant expanses of slick surfaces, these soft-compound Michelin Pilot Sport Cup tires look especially track-ready. That our test car was sprayed in optional Corvette Racing Yellow ($995), festooned with a Carbon Flash racing stripe and Heritage Package ($795) gray hash marks, and bedizened with yellow-painted brake calipers ($595) brought added clarity to what was already abundantly obvious: “Our” $91,655 Grand Sport looked ready to take the green flag. Indeed, in terms of both aesthetics and engineering, this particular Corvette represents the closest a customer can come to ordering a C7.R racecar.

Speaking of the track, our next Thunderhill session beckoned. With the car properly calibrated (frustratingly, we would have to reenter these settings each time we restarted the car), the windows down and helmet on, we headed out onto the circuit. After accelerating down the pit straight and negotiating the deceptively fast Turn 1, we immediately appreciated the lighter steering effort, as it allowed us to get a better feel for what the front tires were up to. Through Turn 2, which slowly arcs a full 180 degrees, we were surprised by how much speed we could carry. We were able to take our preferred inside line and get back on the gas early without a hint of protest from the front tires. Then, over the Turn 3 hill, we encountered far less electronic intervention. Success—we’d seemed to have found just the right configuration. The Grand Sport felt great—responsive, agile and, above all, fast; it practically egged us on to explore more of its exceptionally high limits. With a Porsche 911 GT3 RS up ahead of us, it was time to do just that.

Personality Test 4

Since a GT3 RS packs 500 horsepower and fewer pounds, we knew we couldn’t get past it on the straights. No, this job would have to be done in the corners, as well as the entry into them. The Z07 brakes are phenomenal, allowing us to brake so late and with so much force that we found ourselves wishing for a set of harnesses. To allow optional deceleration, powerful brakes need to be paired with sticky tires, and the Michelins certainly delivered, providing truly racecar levels of adhesion. Our Performance Data Recorder consistently showed the Grand Sport generating 1.2 g of lateral acceleration. With a chassis that adroitly held these French feet to the fire—body roll is minimal and the damping is spot on, thanks to the Magnetic Ride Control shocks—we found ourselves gaining on the Porsche, especially on the new parts of the course where riding the curbs is key to a good lap time. The Z07 suspension laughed off these bumps with seeming indifference, allowing us to confidently remain on the throttle. This trait, combined with the Grand Sport’s incredible directional control, allowed us to make quick work of this technical section, despite our relative lack of familiarity with it.

But we can’t leave the LT1 engine out of the picture, as it played an important role in chasing down the Porsche. We might have been down on peak horsepower, but we were clearly up on torque. With a hefty 465 lb-ft at just 4,600 rpm, compared with just 338 lb-ft at a lofty 6,000 rpm, the 6.2-liter Chevy V-8 has considerable more—and easier to access—twist than the 4.0-liter Porsche flat-6. Though this advantage is somewhat mitigated by the Corvette’s higher curb weight—3,428 pounds versus 3,131—it still allowed us to accelerate out of corners with greater force, at least initially. No doubt, the accessibility of the LT1’s output made the Grand Sport easier to drive compared with the peakier engine in the GT3 RS. For amateur drivers like those involved, this can make a big difference.

The Grand Sport’s ability to translate all that power and torque into forward motion, as opposed to tire smoke, is also part of its track prowess. To be honest, straight-line traction is not usually a Corvette strong suit, but with a chassis designed to handle more engine output and those phenomenally grippy Pilot Sport Cups, the Grand Sport Z07 excels in this category. Thanks to all that stick, we were able to accelerate hard out of Thunderhill’s final corner, grab Fourth gear and hit 130 mph on the front straight. The standard Dual Mode Exhaust sounded glorious as we blasted by the start/finish line. We weren’t left wishing for more power. Actually, we found the feeling of being able to fully exploit the LT1 exceptionally satisfying. Sure, an extra 20-30 horses would have been nice—and should be easily attainable, right, GM?—but another 190 would have thrown off the balance. At our skill level, we knew we’d be leaving too much of the car’s capability on the table.

Personality Test 5

By our third lap of the session, we were in the groove and having a ball—the very point of a track day and, importantly, of having a car like the Grand Sport Z07. At this point, we’d caught up to the GT3 RS. Knowing that this wasn’t a race, we elected not to force a pass, choosing instead to remain a safe distance from the Porsche’s bumper. Nevertheless, the Porsche driver was gracious enough to wave us by, but he had not completely surrendered and proceeded to cling to our tail. Now we were the hunted, and it proved hard to distance the GT3 RS, so evenly matched are the machines. Proof of this point comes in a recent Car and Driver test in which just a tenth of a second separated the two sports cars around Virginia International Raceway, with the Porsche having the slight advantage. A far wider gulf existed between these two vehicles in terms of price, with the heavily optioned GT3 RS stickering for a staggering $195,020, compared with the Grand Sport Z07’s $92,060. And that was for a car without air conditioning or a radio, so extreme were this particular 911’s weight-saving measures. That the Corvette achieved performance parity with a far more expensive Porsche while retaining its host of amenities speaks volumes about what Chevrolet has achieved with the Grand Sport. A world-class sports car? You betcha.

Road Scholar?

When expert driver and Hooked on Driving owner David Ray pulled the Grand Sport into the pits after testing the car (see sidebar), the ambient temperature had soared to 105, yet the car’s engine temp had never climbed above 220. The Corvette had certainly passed that aspect of the test, but the day’s driving was far from over. We’d decided to drive to a nearby restaurant for lunch, then proceed up into the mountains above Willows and see how the Corvette performed on one of our favorite roads. With the temperature reaching a scalding 109 degrees, it was hard to leave the cool comfort of Nancy’s Elkhorn Family Lodge, but Alder Spring Road (Highway 162) beckoned. Plus, we had air conditioning, unlike that Car and Driver 911 GT3 RS, though the optional seat cooler proved largely ineffectual. From Elkhorn, the road meanders through rolling farm fields before making a steady climb up into the Mendocino National Forest, where it becomes entertainingly curvy. With fast Third- and Fourth-gear bends, ample sight lines and stunning forest scenery, Highway 162 proved to be the perfect playground for the Grand Sport Z07. The handling composure, steering precision and abundant grip that makes this model so adept on a racetrack carries over to the road. This Corvette is fast but never nervous; it feels like it can handle anything you throw at it. The only problem is that you’re left feeling like you could have gone 20 to 30 mph faster through every corner, so high are its limits. Because of this, we think the standard, non-Z07 Grand Sport would be more fun on the road, since more of its capabilities could be exploited. If you don’t plan on tracking your wide-body Stingray, it’s the way to go. But even for the occasional track day, the Z07 package is worth the money, and minor foibles.

Personality Test 6

All good things must come to an end. In the case of Highway 161, this comes in the form of gravel: The pavement ceases abruptly near Alder Springs and the 5,000-foot mark. This fact actually saved our butts. We were almost out of gas. With the road steeper than we’d realized and our right foot rather heavy, we’d quickly blown through a ton of fuel. Fortunately, it was pretty much all downhill back to Willows. Just to be safe, we placed the Driver Mode Selector in Eco and crept down the mountain on four cylinders. Actually, we kept it in that mode for most of the drive back to San Francisco, impressed with this Corvette’s ability to live up to its 25 mpg highway rating. This was yet another reason we were glad not to be piloting a C7 Z06 on this day; its supercharged engine can’t switch into V4 operation and is notably thirstier. On the other hand, the freeway is perhaps the one place where the Z06’s 650-horsepower LT4 easily outshines the Grand Sport’s LT1. Stomping on the Grand Sport’s throttle at 60 mph in Fourth gear results in a nice surge of acceleration. Doing the same in the Z06 unleashes a veritable tidal wave of propulsion. On that score, the Z06 has the Grand Sport beat, but we’re not sure those extra horses would have made our day any better, and certainly not on the track.

Actually, we wouldn’t have changed a thing about this particular day in the Grand Sport Z07. Not the 4 a.m. alarm. Not the heat. Not the long freeway miles. As we approached San Francisco and watched the outside temperature gauge fall a full 50 degrees, we reveled in the fulfilling experience we’d had—of wringing out a thoroughbred sports car on street and track—one that is available to owners of this exceptional Corvette.

Editor’s note: To see Gustfason hunt down a Porsche 911 GT3 RS at Thunderhill, visit bit.ly/2wAzYZz

Personality Test 7
Personality Test 8
Personality Test 9
Personality Test 10
Personality Test 11
Personality Test 12

Also from Issue 117

  • "COPO" L-79 C2
  • $10K Buyer's Guide
  • Restored '57 Fuelie
  • Supercharged C6 Grand Sport
  • Small-Block '68 Driver
  • History: Corvette vs. Thunderbird
  • Racing: Antonio Garcia
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