Potent 2014 Camaro Z/28 engineered for track-day heroics

  • 01-Apr-2013 09:11 EDT
2014-Chevrolet-CamaroZ28-017.jpg

The limited-production 2014 Z/28 shares exterior changes common to all 2014 Camaros, most prominently a new front fascia with a wider lower opening and a narrower upper opening. It will be built at GM's Oshawa complex starting 4Q13.

The question of a new Camaro Z/28 wasn’t if, but when. Once Chevrolet had re-introduced the Super Sport nameplate, then the hyper-performing 2012 ZL-1, the return of the iconic Z/28 was only a matter of time. After a long waiting period—the program was back-burnered during General Motors’ bankruptcy work-out—the time finally came in a surprise unveiling March 27 at the 2013 New York International Auto Show.

Developed with a primary focus on track-day capability, the 2014 Z/28 clearly sacrifices civility and occupant comfort for outright dynamic performance. That was part of its design brief. In truth it’s a thinly veiled racecar that just happens to be licensable for street use.

Power comes from a naturally aspirated 7.0-L LS7 V8 originally used in the Corvette ZO6, capable of producing at least 500 hp (373 kW) and 470 lb·ft (637 N·m); SAE J1349 certification is not yet finalized. The car is offered only with a Tremec TR6060 close-ratio six-speed manual transmission. The final drive ratio is 3.91:1.

The Z/28 features various exterior revisions designed to optimize high-speed aerodynamics and improve engine and brake cooling. And in the spirit of the original 1967 Z/28, air-conditioning in the new model is optional—an anomaly among North American production vehicles.

The original Z/28 was created as Chevrolet’s no-frills entrant in the Sports Car Club of America’s new Trans-Am racing series, and A/C—not yet a standard feature in U.S. vehicles at the time—was deleted.

According to Camaro Chief Engineer Al Oppenheiser, in early testing of the 2014 car the development team’s most accomplished driver sliced three seconds off the best test-track laps produced by their reigning speed king, the ZL1. At the car’s debut, Oppenheiser suggested the car is “too track focused for most drivers.”

GM North America President Mark Reuss told the New York show audience that the Z/28’s build sheet “is the wish list of any racer” and he reeled off a long list of technologies including the dry-sump LS7; Brembo carbon-ceramic brakes capable of generating 1.5-g deceleration; integrated engine and transmission oil coolers; considerable aerodynamic work for creating downforce, and a significant reduction in curb weight. As Oppenheiser noted, the new Z/28 is the product of an integrated engineering effort, rather than a collection of trick hardware.

1.05-g grip, spool-valve dampers

According to Z/28 Engineering Manager Mark Steilow, the Z/28 is capable of generating 1.05 g in cornering acceleration, made possible by significant engineering attention to the chassis. He said nearly 200 changes were made to improve on-track performance. It is claimed to be one of the first production cars fitted with racing-spec spool-valve dampers, which enable four-way adjustment of both bump and rebound settings for tuning high- and low-speed wheel motions.

The broader tuning range allowed engineers to dramatically increase the Z/28’s damper stiffness without significantly affecting ride quality. The spool-valve dampers work in conjunction with stiffer spring rates and suspension bushings among other changes.

The vehicle-dynamics team decided to specify 19-in-diameter wheels and tires, which reduce unsprung mass by 42 lb (19 kg) per car compared to the 20-in wheels standard on Camaro SS and ZL1. The smaller diameter wheels also lower the car’s c.g. by 33 mm (1.3 in), which increases handling precision. This is the first production application of Pirelli’s PZero Trofeo R tires, and the 305/30ZR19 rubber used on the Z/28 is claimed to be the widest front tire on any production car.

The Brembo carbon-ceramic matrix rotors measure 394 x 36 mm (15.5 x 1.4 in) in front and are gripped by fixed, monobloc-type, six-piston calipers. The 390 x 32 mm (15.3 x 1.25 in) rear rotors use four-piston calipers. Compared with similar-size, two-piece steel rotors as used on the ZL1, the lightweight carbon discs save 28 lb (13 kg) per car.

Considerable CFD work and time spent in GM’s Warren, MI, wind tunnel helped engineers create a new aerodynamics package aimed at producing downforce at track speeds. The package improves upon the ZL1 aero package with a large front splitter connected to an underbody panel that further reduces lift. Fender flares over the front and rear wheels, extended rocker panels, a rear spoiler, and functional diffuser improve aerodynamic stability.

Reducing curb weight the drag-racer way

Steilow’s team resorted to classic American drag-car construction techniques in its quest to optimize the Z/28’s mass. In addition to the smaller, lighter road wheels, and carbon-reinforced brake rotors (replacing the ZL1’s steel rotors), the engineers also downgauged the backlite glass by 0.3 mm (0.1 in) and specified manual adjusters for the front seats. Determined to keep the Camaro’s 2+2 seating arrangement, they saved 9 lb (4 kg) by replacing the rigid rear seatback and cushion structure with high-density foam.

“We looked at every subsystem for opportunities to save weight,” said Oppenheiser. “Our goal was to get rid of everything that didn’t make the car faster, and keep only what was required by law.”

Other examples of weight savings included eliminating the tire-inflator kit (except for cars sold in Rhode Island and New Hampshire, where it is required by law); removing interior sound deadener and carpeting from the trunk; replacing the standard LN4 battery with a smaller LN3 unit, and deleting HID headlamps and foglights from the build sheet.

Even the Z/28’s audio system was changed to a single-speaker arrangement—“We wanted to eliminate the [audio] system completely, but we had to keep a single speaker for the seat-belt chime to meet safety requirements,” Oppenheiser said.

In total, the team brought the Z/28’s curb mass in at 300 lb (136 kg) lighter than the 4120-lb (1869-kg) supercharged ZL-1 Camaro, and 100 lb (45 kg) under the 3860-lb (1751-kg) naturally aspirated SS model.

The 7.0-L LS7 V8 is hand-assembled in GM’s Performance Build Center. It features CNC-ported cylinder heads, titanium intake valves and connecting rods, sodium-filled exhaust valves, and hydroformed tubular exhaust headers. The engine’s compression ratio is 11:1; operating redline is 7000 rpm.

The V8 breathes through the SS model’s functional hood duct and a racing-style, cold-air induction system with K&N air filter. A dual-mode exhaust system is used. Under acceleration, the exhaust gas bypasses the mufflers, increasing torque and enhancing the acoustic experience.

Part of the mass-reduction focus was to offset the mass of the Z/28’s 10.5-qt (9.9-L) dry-sump lubrication system, which features an integral liquid-to-liquid cooling system. The transmission and limited-slip differential also use a liquid-to-liquid heat exchanger, which reduces differential temperatures as much as 100°F (56­°C). The LSD features a helical gearset, rather than traditional clutch packs, which continuously adjusts torque bias to maximize available traction.

The differential works in unison with Chevrolet’s proprietary Performance Traction Management system, which allows drivers to adjust the level of throttle and brake intervention to match their capability and driving environment.

The Z/28 shares exterior changes common to all 2014 Camaros, most prominently a new front fascia with a wider lower opening and a narrower upper opening.

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