2014 Chevrolet Camaro Z/28 Coupe
Mr. Oppenheiser's high-performance diet plan.
OCTOBER 2013 BY ANDREW WENDLER
Like many of us, the Camaro entered its fourth decade carrying a little extra baggage. Thick in the haunches and laden with the obligatory accouterments of the modern automotive era, Chevrolet still managed to squeeze mind-blowing performance from it, namely in the form of the Camaro ZL1, a car that goes, stops, and turns better than any 4120-pound, 580-hp car has a right to. But for Al Oppenheiser, Chief Engineer of the Camaro program, that was just a warm-up. The next step in the shape-up plan was the Camaro SS 1LE, a lighter, tighter, track-tuned car, followed by the surprise appearance of the even more track-focused Z/28 at the New York auto show. Clearly, Mr. Oppenheiser is not only a man with a plan, but has the friends in high places to make it happen. To give us a taste of its most recent and lightest-weight efforts, Chevrolet invited us out to GM’s Milford Road Course to provide some ballast for a cadre of hot shoes for a Nürburgring-worthy workout in a trio of Z/28s.
Moments into the first hot lap, it becomes apparent that grip was high on the list of the Z/28 team’s objectives. Halfway into the deeply dished turn affectionately known as “Pahrump 2” we’re pulling over 1g, and the chassis remains rock solid. Not only a test of the suspension, this corner was intentionally designed to starve engines of oil, a job it fails at miserably with the Z/28. While the driver and passenger strain to keep the horizon in their sights, the Z’s dry-sump system—the first ever in a production Camaro—remains unfazed, supplying the rotating assemblies of the 7.0-liter engine with a steady stream of motor oil.
Speaking of the engine, it’s no secret that the LS-7 was chosen because it’s 64 pounds lighter than the LSA found in the ZL-1. Producing 505 horsepower and 481 lb-ft of torque (ten more than it makes in the Corvette), its internals read like a who’s who of horsepower weekly: Mahle pistons, K&N air intake
and Pankl titanium connecting rods. Oppenheiser says the connecting rods survived a 50-hour torture test running at redline with little to no wear. Z/28-specific exhaust headers are fitted, funneling into a 3-inch exhaust that tapers 2¾ inches at the rear. Engine oil is cooled by the same liquid-to-liquid system found on the Corvette ZR1. Word is all Z/28 engines will be built at the new GM Performance Build Center in Bowling Green, Kentucky.
Milford’s Nürburgring-like high-speed esses pass beneath us with nary a wiggle or twitch from the chassis. (Check out the Z/28’s 7-minute and 37-second run on the real Nürburgring here.) Much of the credit goes to the 305/30-ZR 19-inch Pirelli Trofeo R tires that reside at each corner. Wheel size is staggered slightly—19 x 11-inch front, 19 x 11.5-inch rear—to improve rear tire handling at the limit. Chevrolet tells us going with the 19-inch tire-and-wheel package saves 48 pounds over a 20-inch setup, and lowers the center of gravity by 1.29 inches. Engineers told us they were experiencing radical tire-bead slip to the tune of a full rotation or more during hot lapping, so they successfully devised a system of knurling the bead area to keep the tires tight. Engineer Mark Stielow says the wear pattern is surprisingly even, which speaks to the overall balance of the package.
But the suspension isn’t just along for the ride; nearly every component has been reworked for the Z/28. Compared to a standard SS, the springs are a whopping 85-percent stiffer in front and 65-percent in the rear, and all of the bushings have been stiffened to improve steering feel and help achieve the car’s 1.08-g maximum lateral cornering figure. Interestingly, the team was able to fit smaller stabilizer bars, down from 28 to 25 mm in front, and 27 to 26 mm out back. Part of the change was made possible by the use of Multimatic DSSV (Dynamic Suspensions Spool Valve) dampers, which make their first appearance in a volume production vehicle in the Z/28. Essentially they trade shims used to tune traditional dampers for shaped ports. The result is improved transient response, thermal stability, minimal fade, easier and more predictable tuning via Multimatic’s proprietary software. Overall, the Z/28 has 190 unique parts in comparison to the SS.
Shifty Motives and Private Diets
Because of the engine’s prodigious output, hyperactive rowing of the close-ratio Tremec TR6060 six-speed transmission was not required to lap the circuit. When needed, however, the driver snicked them off easily, thanks to the combination of double- and triple-cone synchronizers on all gears. First gear in the Z/28 is a 2.66:1 ratio compared with a stock SS’s 3.01, all the gears following suit except for fourth, which is 1.00 for both cars. The rear end carries a 3.91:1 final-drive ratio (the SS’s is 3.45). Using a Torsen helical limited-slip instead of a traditional unit allows for the ABS to function for individual wheel sides and provides rapid torque coupling when powering out of a corner. This change alone cut 0.7 second off the car’s lap times at Milford. A liquid-to-liquid cooler similar to the one in the ZL1 cools both the transmission and the diff. Oppenheiser says a specific break-in plan will be outlined in the owner’s manual to ensure the powertrain and the driveline enter the world with performance and durability in mind.
No opportunity to drop pounds from the Z/28 was overlooked. In addition to the aforementioned weight savings made with the engine and running stock, the team shaved 28 pounds by dumping the A/C (you can still get it as an option), 21.1 by fitting Brembo carbon-ceramic brakes, 10.3 by lightening the rear-seat assembly, 10.1 by omitting some sound deadening, and more through a variety of measures. All in, it weighs 300 fewer pounds than a Camaro ZL1. A specific front splitter, rear spoiler, hood vent, rockers, and fender-lip flares conspire to produce 440 more pounds of downforce at 150 mph than in the Camaro SS.
Lapping the circuit during a cool-down lap, it’s clear that compromise wasn’t a part of the team’s agenda. The car is tight and free of the rattles that often plague track-focused vehicles. The Z/28’s best time on the Milford course is 1:53.71. That’s 2.87 seconds quicker than a ZL1 and 5.14 seconds quicker than the SS 1LE. And here’s where it gets personal: Engineers say the Z/28 betters their best lap time in a 2012 Mustang Boss 302 Laguna Seca by 5.34 seconds.
Oppenheiser says they think they can sell 3000 to 4000 Z/28s over the next two to three years and figures the cars should start showing up in showrooms late in the first quarter of 2014. The Z/28 is expected to be pricier than the ZL1, but firm numbers haven’t been set. When asked if there is a driving principle that keeps him and his team on constant watch, Oppenheiser eloquently replies, “Yeah, to beat the shit out of anything Ford puts on the road. And that goes for the whole company from top to bottom.