At this
spring’s New York auto show, the media at Chevrolet’s press conference expected
the curtain to rise on the Camaro’s mild mid-cycle face lift, which had already
been revealed on a morning TV squeal fest. But when a new Z/28 rumbled onto the
stage, the jaded crowd was so shocked that it erupted in genuine applause. Here
was the return of an American road-race icon, one that got its start as a
homologation special for the SCCA’s Trans-Am series but had moldered through
successive generations. Clearly, Chevy is trying to make up for lost time. The
mission of this car is to help its owner set personal-best laps, and it comes
sporting comprehensive power, handling, and weight-saving modifications—even
outdoing the ZL1 in some regards. When it goes on sale later this year, the
Z/28 will be even more expensive than the 580-hp ZL1, which stickers for
$56,550. Here’s what’s under the skin:
chassis
In a departure from current fashion,
the Z/28 goes down in wheel and tire size, from the 20 inchers on other V-8
Camaros to 19s. Mark Stielow, the Z/28’s engineering manager, explains that
“the 19s are lighter, have less rotational inertia, and let us lower the car.”
The special lightweight wheels are 11 inches wide in the front and shod with
305/30ZR-19 Pirelli P Zero Trofeo R tires all around. Chevy tells us that these
are the widest tires mounted on the front of any production car. A streetable
track tire, the Trofeo Rs have a tread-wear rating of 60 and are manufactured
in the same plant as Pirelli’s F1 rubber.
The Z/28’s suspension geometry is
unchanged from the Camaro SS 1LE, but the spring rates are about 20 percent
stiffer and the car uses Multimatic monotube shocks with F1-style spool valves.
Stielow says this technology provides greater freedom to independently tailor
jounce and rebound settings for low- and high-speed suspension motions.
Anti-roll-bar thicknesses are also up slightly over the 1LE’s, and the bars’
mounts are stiffer.
To both save weight and improve fade
resistance, the Z/28 gets standard carbon-ceramic brakes that are larger and
thicker than even the ZL1’s cast-iron brake rotors. The same TRW electrically
assisted power steering used on other Camaros gets a revised calibration for
the Z/28, and the car has Performance Traction Management, Chevrolet’s
five-level stability-control system. Stielow claims that, with an overall ride
height now lower by 1.3 inches and its very sticky rubber, the Z/28 will corner
at 1.05 g.
powertrain
Displacing 7.0 liters (428 cubic
inches), the dry-sump LS7 from the outgoing Corvette Z06 needed new exhaust
manifolds and a relocated oil reservoir to fit in the Z/28’s engine bay; it
gets stainless tri-Y headers dumping into a dual-mode exhaust system. Chevrolet
promises the engine will produce more than 500 horsepower and 470 pound-feet of
torque. For comparison, Ford’s Mustang Boss 302 makes 444 and 380,
respectively.
The engine is coupled exclusively to
a TR6060 six-speed manual with the same closely spaced gear ratios used in the
1LE package. Also as in the 1LE, the Z/28 uses a 3.91:1 final drive. Instead of
the spring-loaded clutch pack used in the SS and ZL1, however, this car
incorporates a Torsen limited-slip differential to provide a better blend of
low-speed lockup with a more open high-speed action. As in the ZL1, the
differential, transmission, and engine oil are all cooled by heat exchangers.
Stielow promises that the car can burn a complete tank of fuel on the track
without any vital fluid overheating.
weight reduction
The LS7 is about 90 pounds lighter
than the supercharged LSA in the ZL1, and Chevrolet cut mass everywhere it
could. The 19-inch wheels and tires save 42 pounds. The carbon-ceramic brakes
drop 28. Cutting A/C (it can be optionally restored) saves another 20. The
engineers had hoped to leave out the audio system, but keeping the radio and
one door speaker was necessary to bleat mandatory seatbelt warnings. In
addition, the Z gets a thinner rear window and a smaller battery. Trunk
carpeting, a tire-inflator kit, and most of the sound insulation are gone. New
foam eliminates the rear-seat frame and trunk pass-through, saving another nine
pounds. Numerous other weight reductions make the Z/28 a claimed 300 pounds
lighter than the ZL1.
aerodynamics
The most obvious visual cue
identifying the Z/28 is its aero package. There’s a sizable front splitter,
pronounced rocker-panel moldings, a rear diffuser, and a good-sized rear wing.
Small front and rear fender-lip extensions cover the wide wheels and tires.
More than cosmetic, these changes
develop net downforce, versus the Camaro SS, which has about 200 pounds of lift
at 150 mph. Moreover, Stielow says that having more downforce in the rear than
in the front enhances stability. There’s even an accessory Gurney flap that
attaches to the rear wing for more.
Unfortunately, all of this extracts
a drag penalty. While the standard Camaro has a Cd of about 0.35, rising to
0.39 in the ZL1, the Z/28’s is even higher. The aero appendages, the wide
wheels, and the fender extensions add up to a car that “knocks a big hole in
the air,” as Stielow puts it.
performance
Stielow wouldn’t release any
performance claims for the new Z/28, but it’s safe to say that with stickier
tires, better weight distribution, and a power-to-weight ratio only slightly
worse than a ZL1’s, the Z/28 will accelerate almost as quickly. We’d estimate
zero to 60 mph in about 4.2 seconds and a quarter-mile around 12.5 seconds.
Expect top speed to be down from 180 to the low 170s. But on the racetrack, the
Z/28 should be the quickest Camaro of them all. It has already lapped GM’s
2.9-mile Milford Road Course three seconds quicker than the ZL1.
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Courtesy of Car and Driver
