The Big Guns

The fight between the 911 and the Corvette is just heating up in the ALMS. So what happens when you pit the ultimate street versions against each other?

Photo: The Big Guns 1
December 10, 2009

Exiting Turn 4 at Infineon Raceway, I’m flat on the gas in second gear. Short shifts up to third and then fourth come before the braking point for the plunging, left-hand Turn 6 Carrousel, which is hidden just beyond a hump in the road that’s completely blind.

Braking late here might cause the ABS to activate at exactly the wrong time and send this $194,000 997 GT2 into the tire wall. Braking slightly earlier, with lighter pressure, I attempt to carry big speed into the Carrousel. Just as I crest the hill, I downshift quickly to third, trail the brakes, and turn in. The 305-mm Michelin Pilot Sport Cups out back have had all they can take. As lazy oversteer sets in, I’m not worried — just disappointed. The momentum I worked hard for and desperately need to put down a good lap has been wasted.

Turning into the slide, the GT2 rights itself and I roll onto the throttle to get a good launch off of Turn 6. The steering wheel is pointed mostly straight even though the track continues to the left, allowing me to execute a nice drift all the way to the exit curbs heading up the short straight to Turn 7. Just past track out, I’m at redline in third and quickly shift to fourth. The GT2’s 530-hp, twin-turbo six sounds like the exhaust of a jet dryer switched to high. Question is, can this car, the ultimate 911 to date, blow the ultimate Corvette away?

The fight between Porsche and the Bow Tie in the American Le Mans Series is just heating up, but I’ve been thinking about how the latest street-legal 911 track toys stack up against the 638-hp Corvette ZR1 for a while now. Last year, I had the opportunity to drive an early ZR1 at a track day. It was a new car and the owner was a bit timid. Despite the impairments to going after a lap time, I was impressed with the overall feel of the Corvette. This feels pretty good, I thought. But surely a GT2 would be faster around the track. It has to be, right?

I looked into it and found solace in the fact that Walter Röhrl turned an amazing 7-minute, 32-second lap at the Nürburg­ring in a 997 GT2. I couldn’t find mention of a ZR1 ’Ring time anywhere, though. Surely GM would have touted a quicker time if it had one. Before long, magazines began getting their hands on ZR1s and echoed my thoughts. I kept telling myself the GT2 had to be faster around a track.

Then it happened. At a race last year, Porsche Motor­sport’s Roland Kussmaul, the godfather of modern racing 911s, showed me a video of a ZR1 lapping the ’Ring with GM test driver Jim Mero at the wheel. As I watched the video and listened to the supercharged 6.2-liter V8’s scream, Mero laid down an incredible lap. The clock stopped at 7:26.

Photo: The Big Guns 2

After watching the video, I still couldn’t believe that a ZR1 could beat a GT2 on track. Or most tracks, anyway. For one, the Nürburgring has a straightaway longer than the full length of most tracks in North America — and the Corvette’s 108-hp advantage could make up the difference on that straight alone. Next, who really knows what kind of chicanery manufacturers go through in order to achieve a top time at the ’Ring?

This year’s wild ALMS finale at Laguna brought my curiosity to a boil. I asked Scott Mercer, a friend and student who happens to have both a GT2 and ZR1 in his collection, about his willingness to pit his cars against each other. As always, he was game to see a race.

So less than a month after the epic Porsche-Corvette finish at Laguna, a customer GT2 and customer ZR1 are sitting on pit lane at Infineon Race­­way in Sonoma, California on a beautiful fall day. This 2.5-mile road course is known as a “handling” track. What it lacks in straights it makes up for in blind crests and really fast sweeping corners.

To learn as much as possible, I wanted to use data acquisition to record every good lap — and every mistake. Subjec­tive feedback is one thing, but data provides an objective measure in addition to lap times to determine where each car’s strengths and weaknesses are. I called Kenny Gorman of Gorman Motor­sports, who specializes in all things data for race cars, and he agreed to come out and monitor the test with the GPS-based Traqmate system.

With the Traqmate fired up and ready to go, I settle back into the familiar GT2. The cabin, equipped with shell bucket seats and proper belts for the track, feels spacious yet intimate. The driving position, ergonomics, and view out the windshield, in fact, are very similar to the GT3 RSR I’m used to. Acceler­ating out of the pits, the thrust in second is impressive by any standard.

Driving hard on the out lap, I’m using the brakes and throttle aggressively to generate heat in the brakes. The GT2 drives like a very well tuned GT3 RS with more power and more weight over its rear tires. Exiting Turn 11, the last turn on the circuit, I plant my foot to the floor and, after very subtle turbo lag, the GT2 plants itself on its rears and rockets towards Turn 1. The amount of available grip exiting slow corners is fantastic.

Photo: The Big Guns 3

With 530 hp and 503 lb-ft of torque, the GT2 is the most powerful production 911 yet. Critically, the rear-engined, rear-drive supercar can use all of it. That makes exiting Turn 2 an experience akin to roller-coaster acceleration — fast and deliberate, with a sense of hooked-in forward momentum that only gets more intense. In fact, the GT2’s rear-end grip is so good that it tends to cause power-on understeer, which isn’t helped by the off-camber exit of Turn 2.

Heading into Turn 3, a left-hander with a downhill turn-in that rises dramatically just past the apex, the GT2 is settled. When I touch the inside curbing, the car easily swallows the curb in a way that reminds me how unbelievably tough Por­sches are. With each shift, turn of the wheel, or press of the brake pedal, the GT2 taunts you to push it harder.

Coming down Infineon’s high-speed esses, the GT2 feels slightly unwilling to turn into Turn 8. What initially feels like mild understeer is really just a need to turn the steering wheel more aggressively. Before the GT2 has a chance to compose itself, I turn quickly to the right into the very quick 8A. The quick left-to-right weight transfer takes some timing and patience in order to avoid upsetting the chassis. Like all 911s, the GT2 regains its composure once I’m back on the gas.

Turbo-boosting my way through Turn 9 — a fast, fourth-gear left-hander — I concentrate on getting over to the left side of the track to set up for the entry to Turn 10, another fast fourth-gear turn, this time to the right. At turn-in, the back end begins to step out, but it can be corrected quickly with countersteer. At the limit the GT2 is predictable, but the window of available traction is small. At five degrees of slip angle, the GT2 is easy to control and place on the track. Beyond that threshold, it becomes less stable with each additional degree of rotation.

My seat-of-the-pants diagnosis is that this phenomenon is tire-related. It seems that once the Pilot Sport Cups’ surface temperature surpasses a certain value, grip diminishes rapidly. The front axle of the car never suffers from the temperature-related drop-off in grip. But with a 38.5/61.5 weight distribution, the front tires aren’t getting used like rears are.

Variable-vane twin turbochargers and electronic fuel injection are marvels of modern engineering, producing a powerband that’s smooth and consistent from idle to redline. Some reviewers claim the 997 GT2 has virtually no lag. On the street, its lag is detectible but not obvious. On the track, however, it’s more pronounced. Exiting Turn 3, I flatten the throttle to get a squirt up the hill to 3A. The expected rush of acceleration comes, but it comes three tenths of a second later than I expect. The delay in power delivery is noticeable in the esses, too, where I have to lift slightly followed by going back to power immediately. Anytime I lift, boost pressure is lost and that hesitation is the system recharging itself. With a slightly different driving style, the minor lag can be negated and Infineon can be negotiated at a blistering pace.

Photo: The Big Guns 4

In this case, the GT2’s three laps stand at 1:49.8, 1:49.8, and 1:49.2.

Jumping out of the GT2 and into the ZR1 requires a lack of preconceived ideas. If you’re familiar with a Por­sche, everything about the Vette is different. Sitting in the ZR1 feels foreign at first. Its hood is big, the cabin snug-fitting, and the steering wheel…well, it’s the same wheel the last Chevy Cobalt I rented had. Really, GM? In a $105,000 car, the one thing you look at and touch most is the same found in a Cobalt?

Admittedly, I’ve never been a huge Cor­vette fan. When I was growing up, they were big on the outside, small on the inside, heavy, and not fast. In 1973, the Vette tipped the scales at 3,400 pounds. The optional 7.4-liter V8 made 275 hp while the base 5.7 made an anemic 190. Good thing it wasn’t fast, because a modern-day, bargain-basement Kia will out-handle and out-stop it. Of course, like all auto­makers, the General had some good and bad years. But, despite continuous improvements, I never aspired to own a Corvette. Or, frankly, even drive one.

In 2001, all that changed. I coached a guy who club-raced the first-generation Z06 in the SCCA’s T1 class. A T1 car was essentially a showroom stocker with safety equipment and R-compound rubber. It wasn’t the power or brakes that I found impressive — it was the cornering speed and balance. The 2001 Z06 was far from perfect, but it gave me a healthy respect for GM’s capabilities.

Today’s ZR1 has a push-button starter that brings its massive V8 to life. Once running, it’s got a relatively quiet and gentle idle. You wouldn’t really guess that 6.2 liters, a supercharger, 638 hp, and 604 lb-ft of torque are hiding under the hood. The latter give the 3,324-pound ZR1 a better torque-to-weight ratio than Porsche’s almighty V10 Carrera GT.

After selecting first gear, I let out the clutch and I’m surprised by how easy and progressive the clutch release is. Pas­sing pit out and heading up the steep approach to Turn 2, I stand on it in second and easily get wheelspin. I don’t know what I’m more impressed by — the wheelspin in second or the sound that the supercharged engine produces. Past 3500 rpm at full throttle, a roar envelops the cabin that gets louder and meaner all the way to the 6500-rpm redline.

Photo: The Big Guns 5

Heading around the track on my out lap, the ZR1 has a quality that’s hard to put my finger on. It feels supple on track but not necessarily soft. There’s a lot of dive under braking, but it upsets neither the chassis nor its balance. The magic ingredient must be the ZR1’s Magnetic Selective Ride Control. The real-time system swaps the standard Cor­vette’s conventional dampers for units filled with a fluid that contains iron particles. Under the influence of a magnetic charge, the particles produce instantaneous valving changes. With a cycle speed of a thousand times per second, MSRC is claimed to be the fastest-reacting active damper.

Because I’m not as familiar with the ZR1 as with the GT2, my out lap is more reserved. That leads to questions about how it’s going to behave once I pick up the pace. Exiting Turn 11, I roll onto the throttle carefully, feeling for traction coming off of this second-gear corner. Get­ting the Vette on the limit with the throttle is easy to achieve and highly predicable. After about 60 mph, I feel confident that I can plant the accelerator to the floor. The ZR1 pulls hard, never dropping off through second, third, and fourth gears until I run out of track heading up through Turn 1 on my way to Turn 2.

The ZR1 comes on Michelins, too, in this case the Pilot Sport PS2 ZP (for zero pressure) — a run-flat tire designed specifically for this model. Read­ing the sidewalls, the wear rating for the Sport Cups on the GT2 is 80 where Michelin rates these PS2s at a relatively hard 220. Heading through Turn 2, I don’t have quite the grip of the GT2, but tire-related grip is far better than I thought it would be.

Turning into Turn 3 seems to upset the ZR1 slightly, almost as though MSRC is confused for half a second. At the exit, I go for a squirt of throttle and am immediately rewarded with generous forward momentum. The supercharged engine provides the throttle response of a GT3 RS with the torque of the GT2 — a great combination on track.

Turning into Turn 4 — a downhill, off-camber 90º second-gear right-hander — I carry a bit more speed than anticipated. Rather than overshoot the apex, I roll off the brake and turn in. The ZR1 turns in without hesitation. The amount of speed you can carry at turn-in is truly impressive. Ironically, it’s similar in technique to driving a GT3 RSR on Michelin slicks.

Exiting the Carrousel in third gear at about 90 mph, I roll on the power and get power-on oversteer! It’s easy to correct but, as with the GT2, the ZR1 requires you to bring all of your driving skill to the table when you’re at the limit. Heading into Turn 7 well into fourth gear, the V8’s noise is intoxicating. It’s the American answer to the GT3 RS’s song, a sound you can’t wait to share with friends and one that puts a smile on your face.

Photo: The Big Guns 6

The speed it offers will, too. It’s a good thing the ZR1 has carbon-ceramic Ferrari FXX brakes up front and Enzo brakes at the rear, because I’m heading into Turn 7 at a very high rate of speed. The huge rotors and calipers slow the ZR1 down with authority. When the ABS cycles, it feels as though it does so much more slowly than the Porsche system. The system’s distinctive lock-release characteristic reminds you that you overshot the corner and are on the verge of being in trouble. The Porsche’s ABS system, by comparison, is much less intrusive.

The Corvette’s balance through Infi­neon’s esses inspires a lot of confidence. Turn-in is immediate, the transitions easy to predict and control. If you get a bit of understeer, it’s easy to make the ZR1 neutral with the throttle — at any speed and in any gear. In fact, the ZR1 is the only car in which I’ve achieved power-on oversteer at Infineon’s Turn 9, a fast left-hand fourth-gear bend. It could be the lack of rear downforce, but I don’t think that its absence is a contributor. More likely, it’s the street tires and 604 lb-ft at 3800 rpm. In all cornering situations, judicious throttle application is required to drive the ZR1 in a neutral state.

Getting used to this Corvette on track takes surprisingly little time. I continue to push the car harder and, when I overstep its limits, it communicates clearly and gently. My laps around Infineon net a 1:49.2, 1:49.2, and a 1:48.8. The times are remarkably close to the GT2’s, this despite the fact that GM has gone about going fast in a completely different manner. An overlay of the data illustrates just how differently these cars achieve their lap times (see sidebar, p. 61).

Sitting on the pit wall, watching the heat wiggle the air over the hood of the ZR1 and above the decklid of the GT2, I’m struck by how incredible these cars are. Based on prior experience, I knew that the GT2 was going to be good at Infineon. And it was. However, I wasn’t sure what to expect from the ZR1. Based on previous experience, I knew it would be fast and I knew the critics were saying good things about it. What I didn’t know was how the ZR1 would behave when pushed hard on the track.

As a Porsche fan first and a racing driver second, I have to admit that I’m taken with the ZR1. It’s been said that the ZR1 is the best car GM has ever built. I can’t comment on that, but I can say that it’s by far the best GM vehicle I’ve ever driven — on and off the track.

The battle for the best lap time around Infineon goes to the ZR1, but the war will rage on. After all, these are cars that were designed to be driven on the street, and a lap time around a race track only tests their extreme performance envelopes. As I drive the ZR1 home after the test, I detect a small exhaust leak. It may have won this track contest, but it looks like it has a little ways to go before it can claim the title as the most complete high-performance car of them all.

Also from Issue 180

  • The Forgotten 911 SC-L 3.1
  • 997 Sport PASM vs. regular PASM
  • Preview: 2011 Boxster Spyder
  • Troutman-Barnes four-door 911S
  • Patrick Long 2010 GT3 Cup Tire Test
  • Modified 997 GT2
  • Market Update: 1989–98 911
  • Interview: Dirk Werner
  • Project Cayman: Lightweight Seats
  • How Not to Own a 944, Epilogue
  • Tech Forum: TPMS Part 1
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