2015 Chevrolet Corvette Z06 Automatic First Test
Beauty in the Blasphemy
There are plenty of things that will induce a car enthusiast to cry "blasphemy" or "sacrilege," but few are more effective than putting an automatic transmission in a hard-core sports car. To some, a dual-clutch gearbox is bad enough, but a torque converter? Burn the witch. Or should you?
Chevrolet's Corvette team has been putting automatic transmissions in their cars for decades, but never in the hard-core Z06 model. This changed for 2016 with the invention of a house-built eight-speed automatic Chevrolet insists is strong enough, fast enough, and smart enough to earn a spot between the Z06's rear axles. Purists are understandably hesitant, but years of proven dual-clutch automatic performance have softened some hard souls. Still, a torque converter? A slushbox?
Not just any slushbox, Chevy says. This eight-speed shifts quicker than Porsche's PDK dual-clutch, a benchmark in dual-clutch transmissions. It does clever things such as changing gears while two wheels are in the air, as we found in our first track test at Road Atlanta. It's a whole new animal. But how does it perform?
First, we should note two important caveats. As recently discussed in length, the manual-transmission Z06 that Chevrolet recently sent us to test had an alignment problem in the rear end that affected its performance on the racetrack, as demonstrated in the retest. This car was double-checked for the problem and received a clean bill of health. Second, this car has been programmed with a new Rough Track mode developed after additional testing at older, rougher tracks. This softens the dampers in Track mode. The new program will be made available in the near future through the Chevrolet Performance Parts catalog.
To the numbers, then. From a standing start, our automatic Z06 hit 60 mph in 3.2 seconds, matching the quickest manual-transmission Z06 we've tested. Chevrolet has claimed the automatic can hit 60 mph in less than 3 seconds, but we must assume they were using a prepped surface. We test on standard asphalt to better approximate real-world performance. The automatic Z06 crossed the quarter-mile mark in 11.2 seconds at a speed of 127.0 mph, besting the quickest manual we've tested by 0.1 second and 0.8 mph. Credit those incredibly quick upshifts.
Stopping the car proved even more impressive. This Z06 needed a record-tying 90 feet to stop from 60 mph, besting both manual transmission Z06s we've tested by a foot.
Handling is where we expected to see the biggest difference, but it came in the driving experience rather than in the numbers. The numbers say this automatic Z06 matched the manual cars' best performance on the skidpad in pulling 1.17g average. In our figure-eight test, it was actually the slowest Z06 yet tested by a tick, putting down a 22.6-second lap time at 1.01 g average. It was, however, incredibly consistent in its figure-eight lap times, something that can't be said for the car with the alignment problem, which also happened to be the car that posted the quickest Z06 lap. We're beginning to suspect that 22.3-second lap was a perfect lap, as the other cars have consistently been in the 22.5-22.7-second range. Regardless, anything under 23 seconds is screaming quick and among the fastest we've ever tested.
In addition to the consistency in figure-eight lap time, the big difference was in how the car drove. The chassis was far better balanced and neutral with no obvious tendency to under- or oversteer at corner entry or mid-corner. Aggressive throttle input can provoke a power oversteer at exit, but it's predictable, smooth, and easily controlled with quick hands. It was a welcome improvement from the badly aligned car, which would pop loose at turn-in and have to be managed all through the corner. With this car, you brake late, turn in, go to maintenance throttle, and power out judiciously, just like every driving instructor has ever taught you, and the car responds exactly as it's supposed to.
Given the myriad computer aids available on this car, we tried lapping it both in Manual and Automatic modes, as well as with and without the Performance Traction Management (PTM) and its Track mode. The lap times were essentially the same, though we found it more fun to shift manually and to disable the PTM entirely, as we found the crutch encouraged sloppy throttle application (though with enough practice, it could be a handy aid in the right hands).
We also found the automatic transmission to be geared shorter than the manual. Whereas the manual car could complete a figure-eight lap in second gear only, the automatic needed to get to third. Left to its own devices, the transmission was fine, but we found in manual mode it could be a bit slow to react to the paddles when a downshift was requested.
Adjourning to the race track, we found the automatic Z06 a compelling performer at Willow Springs International Raceway's Big Track. With a proper alignment and Rough Track mode, it lapped the "Fastest Road in the West" in 1:25.76, 0.06 second slower than the Nissan GT-R NISMO and 0.7 second slower than a properly sorted manual transmission Z06. Given that Randy Pobst lapped this automatic Z06 first and the properly sorted manual Z06 second, we believe he may have been able to come closer to the manual car's time or even match it if we had more track time, based on his increased familiarity with and confidence in the car.
"This car is far better than the last one we drove here," Pobst said. "It's putting power down far better than it did last time. The traction under acceleration is far better. This time, I had the confidence to have a sense of downforce in the fast corners, especially 8 and 9, that the car was kinda hooked."
He added: "The car is still, in my opinion, a little bit oversteer-y. It should be, in my opinion, a little bit understeer-y, especially so you can keep your foot in it when you're going around a corner -- you can use more power -- so it doesn't go to oversteer as quickly."
Even still: "I still don't experience a push anywhere. All the way around the Turn 2 carousel, it feels like I have very little steering in the car. Really balanced. Even the tail, the tail may be coming, but in a no-fear kind of way, like, 'Wow, this thing's really balanced!' "
With regard to the automatic transmission, he was generally positive.
"The automatic is really easy," he said. "It makes it so easy. Except on the first two laps, it got lazy on the three-four shift coming out of 9. Drove me crazy, but then it went away. It was on full automatic, and it hung on the redline. It just hung there, then it shifted. It felt like forever. I was driving slower on the out lap to protect the tires, so the transmission said, 'Oh, you're not going flat. I'm gonna shift up.' Maybe that's what confused it, but it did it the second lap, too, which was hot. The third lap it didn't do it, though. But maybe that's why. It took the transmission awhile to realize 'I'm at a racetrack.' It's pretty sweet, other than that. Man, it works great."
There was still a matter of engine oil temperature, though, which plagued the other Z06s we've tested. Per Pobst, the oil temperature nearly redlined after a few laps, topping out at more than 320 degrees. Taking a cool-down lap brought the temperature back down, and the car was good to go again, but that's not ideal. Moreover, he reported "the power still falls off significantly after the first lap" after the engine gets hot. We checked the data, and lap times and peak speeds did fall off by a few tenths of a second and 1 or 2 mph on each subsequent lap, though these could also be attributed to tire wear and other factors.
Corvette chief engineer Tadge Juechter recently explained to fans that the automatic transmission cars run hotter than the manual transmission cars and will go into an engine-protection mode sooner, though we've encountered the same issue with the manual transmission cars. Juechter also suggested the car is optimized for performance in ambient temperatures of 86 degrees or lower. The high on our test day was 70 degrees. Although Pobst has consistently complained of reduced engine power when lapping C7 Z06s, the problem does not appear to be especially great (in terms of lap times), and it only seems to affect drivers of Pobst's incredibly high skill, so most customers won't encounter it.
All that aside, which car would Pobst choose for track duty? "Automatic 'cause I have fifth gear," he said. "If I'm at a track where I don't need fifth, I might prefer the manual because I like the level of control." Pobst's issue with fifth gear was repeatedly hitting the dead space between fifth and seventh when attempting a four-five upshift at race speed with the manual transmission.
So that's what the racing driver thinks, but what about the mere mortals? We, too, like the automatic Z06 very much. Around town, it shifts very smoothly and is always ready to give you power if you request it, regardless of driving mode. The one-two upshift is occasionally stiff if you're aggressive with the throttle, but it feels as though the transmission is doing it to feel sporty rather than simply misbehaving. Driven hard, the transmission is very smart about which gear to be in when. Pobst had no issue with its gear choices on the track, and neither did we. From a driver's enjoyment perspective, we don't see any big drawback in choosing the auto over the manual, given that anyone making such a choice probably isn't a manual transmission purist to begin with. All that said, we did mention earlier the car responds a bit slowly to paddle shifter inputs, and its downshifts aren't dual-clutch quick, which some may find mildly frustrating. Finally, puttering around town with the exhaust valves closed, the automatic's choice of high gears and low rpm for fuel economy tends to create a droning exhaust tone that can get tiring. Best to drive it in Sport mode or lock those exhaust valves open.
All told, the Corvette Z06 automatic is a fantastic performance car and completely worthy of its coveted Z06 badge. The automatic transmission presents no serious detriment to even the above-average customer and can be just as fun to drive as the manual in the right hands. Chevrolet promised a car that drives and performs just as well as its manual transmission sibling, and this car just about delivers. It's not quite perfect, but damn is it close, and we have a feeling it will only get better.
|2015 Chevrolet Corvette Z06 Automatic (Z07 Package)|
|VEHICLE LAYOUT||Front-engine, RWD, 2-pass, 2-door coupe|
|ENGINE||6.2L/650-hp/650-lb-ft supercharged OHV 16-valve V-8|
|CURB WEIGHT (F/R DIST)||3,550 lb (49/51%)|
|LENGTH X WIDTH X HEIGHT||177.9 x 77.4 x 48.6 in|
|0-60 MPH||3.2 sec|
|QUARTER MILE||11.2 sec @ 127.0 mph|
|BRAKING, 60-0 MPH||90 ft|
|LATERAL ACCELERATION||1.17 g (avg)|
|MT FIGURE EIGHT||22.6 sec @ 1.01 g (avg)|
|EPA CITY/HWY/COMB FUEL ECON||13/21/16 mpg|
|ENERGY CONS, CITY/HWY||259/160 kW-hrs/100 miles|
|CO2 EMISSIONS, COMB||1.24 lb/mile|