Join Date: Nov 2004
2016 Cayman GT4
2011 Chevrolet Corvette SLP ZL610 Full Test
"Be careful of that thing. It'll break the rear tires loose on the two-three shift and gets squirrelly. It takes absolutely nothing to spin the tires even with traction control on."
"The transmission's a little rough with its shifts. I thought there was something wrong with it.... There wasn't. It doesn't take a lot to get in trouble. Be careful."
These are the sort of warnings that come attached to the keys of the 2011 Chevrolet Corvette SLP ZL610. There's a tone of foreseen doom you'd expect to hear just before entering an alligator sanctuary or your first date with Lindsay Lohan.
SLP's most powerful tuner Vette would seem to be equally explosive. And with 610 supercharged horsepower, it most certainly is, but is this really the scary doomsday machine it was made out to be?
Getting To Know You
To find out, a trip through the Santa Monica Mountains is mandatory. Kissing a rosary is optional. The first test is a tough one: a tight, winding uphill road with oh-so-close canyon walls and hairpin turns designed to entice cars like the ZL610 to perform a taillights-first pirouette at the drop of a flat-bill hat. This will be the get-to-know-you run: one of throttle prudence that'll serve as an education on the car's grip.
Quite frankly, it seems docile enough. The throttle is not a hair trigger. There's a nice, progressive response that requires you to really lay into it to discover the overabundance of power. In the nice-and-easy early going, though, the transmission calls attention to itself. Unlike those of most performance cars nowadays, the Corvette's torque converter auto is decidedly old school and doesn't seem suited to the task at hand. Both regular and Sport modes seem to be programmed for fuel economy, upshifting to top gear at its earliest convenience and being generally recalcitrant to downshift.
Manual mode is the obvious solution to this, and it does match revs when you downshift it yourself, but its paddle shifters are leftovers from the days before everyone agreed that Ferrari had it right with its left-pull downshift/right-pull upshift setup. In the Corvette, there are paddles on each wheel spoke, but you push either for an upshift and pull either for a downshift. This was a silly design in a Saturn Aura and it's absolutely obtuse here.
A shift to 5th means it's probably going fast enough to land in the Lost Hills Sheriff's impound yard.And yet, this transmission is nevertheless key to the ZL610's appeal. By now you might be asking why anyone would bother with the 610-hp, $117,860 ZL610 with SLP's TVS 2300 high-output supercharger when there's an unmolested, factory-spec also-supercharged 638-hp Corvette ZR1?
Well, besides costing about $5,700 less, SLP offers variety. Want a ZR1 convertible or one with a targa roof? Too bad. Want an automatic transmission? Forget it; row your own damn gears. The ZL610, however, can provide ZR1 speed with sun and a six-speed automatic.
And you buy it just as you would a ZR1, at your local Chevy dealer, although SLP will only build 250 examples. They even come with a five-year/100,000-mile powertrain warranty and a three-year/36,000-mile warranty on all other components. By the way, that's the same warranty coverage GM gives you on a ZR1.
The Pace Quickens
Yesterday, inching the Corvette through downtown Los Angeles, its automatic transmission was our favorite piece of the car. Right now on this mountain run, not so much.
On the upside, operating the transmission is barely needed in these conditions. With such a mountain of torque on hand, you can simply leave it in 3rd or 4th to keep things smooth. A drop to 2nd only encourages the aforementioned pirouette, while a shift to 5th means it's probably going fast enough to land in the Lost Hills Sheriff's impound yard. First gear, you say? We'll get to that later.
As the road straightens a bit and the canyon walls retreat to a more comfortable distance from the wide Vette's chunky fenders, the SLP ZL610 starts to feel more in its element.
Its brakes are superb, part of the $8,995 Brembo brake package SLP will attach to the car that includes 15-inch rotors with six-piston fixed calipers front, and 13.6-inch rotors with four-piston fixed calipers rear. At the track they brought the ZL610 down from 60 in 104 feet, while in the mountains they proved to be absolutely fade-free. Pedal feel is lacking, but that's typical for a Vette.
As the colossal amount of grip increasingly builds trust, each turn seems to require less and less braking. With the fat 20-inch Michelin PS2 ZPs at the back, the SLP ZL610 circled the skid pad with 1.02g of grip. That's better than the Grand Sport's 0.98, the same as a ZR1 and a bit less than the Z06 Carbon's 1.04.
Initial turn-in response should be sharper, but weighting and feel are excellent once speeds increase or more steering is needed. As the wheel begins to unwind to center, it's finally time for those 610 horses. Again, this is not a matter of stomping on the throttle. Just as we discovered when launching it at the track to the tune of a 4.0-second 0-60 time (3.7 seconds using 1 foot of rollout as on a drag strip), one must smoothly and progressively feed the power to establish grip and then let 'er rip.
However capable the tires and brakes may be, it's the power in the straights that allows this Vette to put away for good whatever car that thought it could keep up with you.
Unleash the Horses
As the numbers on the head-up display blink upward, the noises filling the cabin are frankly a little underwhelming. The prideful, all-American warbling roar you might expect is replaced by a rather muted supercharger whine that's more GT-R in tone than old-fashioned pushrod. And this is with SLP's "PowerFlo" exhaust system.
If anything, the sonic impression left by this car is the droning that occurs any time you leave the car in Drive. With 5th or 6th gear perpetually on tap, the barely revving engine emits an impossibly deep, canal boat grumble.
Perhaps you'd want a more pleasing exhaust, but it's hard to fault an engine that delivers the ZL610 through the quarter-mile in 11.8 seconds at 121.1 mph (a ZR1 does it at 11.7 at 126). It's absolutely intense and obviously contributes to this car's ability to recalibrate your sense of speed. With confidence increased, yet prudence (and traction control) still engaged, SLP's Corvette rarely approaches its limit on our drive.
Despite this, a trailing BMW M3 and later Yamaha R1 quickly disappear in the rearview mirror, even as the road once again becomes tighter and twistier. The ZL610's best slalom number of 72.7 mph, which was actually accomplished with stability control on, really doesn't do its handling abilities justice.
Break Out the Calculator
What's all this cost, however? Well, it starts with either a base C6 or a Grand Sport. Our car was the latter with the 4LT package that stickers for $65,495. To that SLP adds the $21,995 standard package of supercharger, suspension, exhaust, hood window and lip spoiler. It's then $7,995 for the ZR1-style front splitter and side skirts, $5,995 for the forged alloy wheels, $2,995 for the tires (you've been warned), $3,495 for the very comfortable two-tone Alcantara sport seats, $895 for the suspension lowering kit and $8,995 for the brakes. By our calculator, that works out to $117,860.
That's a spicy meatball, but unlike so many tuner cars, you don't get something that's been made worse with these additions. Frankly, it's hard to differentiate between GM's bits and SLP's pieces. It's all very well done, except for the two-tone steering wheel, which looks and feels like a Pep Boys special.
Ultimately, this Corvette offers ZR1 speed, handling and comfort, while giving folks body style and transmission options.
And it draws a crowd, despite being reasonably subdued for a tuner car. The red paint is obviously quite flashy and the side gills are hard to miss, but SLP thankfully doesn't slap on a bunch of SEMA-worthy visual nonsense. The 20-spoke rims are tasteful, the rear lip spoiler is subtle and SLP's special hood, which pays homage to the legendary L88 Corvette from 1968 and '69, is as much about history as histrionics. Its ZR1-inspired hood window also showcases actual metal rather than a cheesy piece of engine-covering plastic GM displays.
The result is an autograph session at every gas stop.
Commence the Burnout
As the road approaches its finale, the time comes to lose some of that colossal grip. Welcome to the party, 1st gear, whose application can pretty much be restricted to use at such moments when caution is thrown to a wind quickly filled with tire smoke. Traction control off, transmission in Sport, pull a paddle down into 1st, left foot on the brake and progressively lean into the throttle. Feel the car squirm a bit and stomp on it, staying on the brake just long enough to create what photographer Kurt Niebuhr described on the scene as an "apocalyptic burnout."
Fittingly, this is the type of scene envisioned before setting out in this forewarned doomsday machine. Not only is it possible, but it's hilariously easy to do. Yet you have to consciously try to do it — or at the very least, be so stupid and/or inattentive enough with the throttle to have the ZL610 bite you. It may be a doomsday machine, but it's a controllable one.