It’s not rocket science: Low body-chassis weight plus high horsepower equal exhilarating performance.
The combination of low weight body and chassis components plus increasing the output of high performance engines with considerable aluminum content, has defined the Corvette for six decades. With a curb weight of only 3,199 pounds and 505-horsepower, the 2013 Corvette Z06 is not only one of the lightest sports cars available in America, it boasts one of the best power-to-weight ratios (6.33-to-1). That’s better than the Aston Martin DBS (7.5-to-1 – 510 horsepower/3,836 pounds), Porsche 911 Turbo S (6.7-to-1 – 530 horsepower/3,561 pounds) and Nissan GT-R (7.1-to-1 – 545 horsepower/3,887 pounds).
“Horsepower isn’t the only measure of performance,” said Harlan Charles, Corvette’s marketing manager. “Balance and low weight are just as important and that’s where the Corvette excels. It has a heritage of employing cutting-edge technologies and materials to help optimize performance.”
Corvette’s use of advance materials began with the very first Corvette in 1953, right, produced with an all-fiberglass body. Every Corvette since has featured a composite-material body. Legendary designer Harley Earl first considered the lightweight, rustproof composite material, for use on a GM vehicle. Besides being an exotic choice for the early-1950s and having an undeniable weight advantage, fiberglass offered an economical way to create the low-volume Corvette without the expense of large sheet metal stamping dies.
Starting with the third generation in 1968, body parts were manufactured using a press mold process, whereby the fiberglass material and resin were shaped in a die-like tool that produced smoother parts more quickly. It was a significant advancement in forming technology and laid the groundwork for a change in the body panels’ material in 1973. That year, the composition changed from conventional fiberglass to sheet-molded composite, or SMC, which was composed of fiberglass, resin and a catalyst formed under high heat and pressure. The ratio-of-resin to fiberglass was reduced with SMC, while the fiberglass itself was a bit coarser. The new material helped produce panels that were smoother right out of the mold, resulting in higher-quality paint finishes.
All Corvettes since 1973 have used SMC body panels, but the material composition has changed dramatically, featuring less traditional fiberglass and more lightweight plastic. The early SMC material created parts that were stronger and more rigid, but more brittle. As SMC technology and production experience evolved, Corvette engineers were able to alter the material composition and the body parts’ specifications to trim the Corvette’s curb weight. Mostly, that happened through making thinner body panels, because SMC was denser and stronger than conventional fiberglass.
It’s rare that a next-generation model of any vehicle is lighter than its predecessor, but that was the case with the fifth-generation (C5) Corvette in 1997. In fact, the 1997 Corvette was larger overall – longer and wider – than the 1996 model, but it weighed nearly 100 pounds less. A greater emphasis on advanced materials was the reason.
The C5’s panels were exceptionally light, but so was the Corvette’s all-new chassis, which used beefy rails and hydroformed sections to provide strength with less complexity and weight. The floor sections used a sandwich of materials including featherweight balsa wood – a renewable material – to minimize mass. That continues with the C6.
Even the C5’s Gen III small-block V-8 contributed to weight savings and overall greater balance. Compared to the Gen II small-block it replaced, it featured a lightweight aluminum cylinder block, aluminum heads and a composite intake manifold that weighed less than 10 pounds. The Gen II engine used a heavier iron cylinder block and aluminum intake manifold. A lighter engine improved the front-to-rear weight balance. Corvette C6 LS2 engine, below.
The C5 also introduced titanium and carbon fiber to the Corvette. The 2001-‘04 Z06 used a 26-pound titanium exhaust system that was 70 percent lighter than the conventional muffler/tailpipe assembly of other models. A lightweight carbon fiber hood was used on a special-edition 2004 Z06 and it was nearly 11 pounds lighter than the already lightweight standard SMC hood.
The introduction of the C6 Z06 in 2006 brought an aluminum-based chassis structure and a greater percentage of carbon fiber body panels, representing the most significant advanced materials initiative in Corvette history. Despite looking like the steel chassis of the base Corvette, the C6 Z06’s aluminum frame weighs nearly one-third less. Magnesium is used for the roof structure, engine cradle and some of the other suspension attachment points for greater mass reduction. On the outside, the Z06 uses carbon fiber panels for the front fenders, front wheelhouses and rear fenders. Rare 1 of 100 built 2009 Special Edition GT1/Z06 Corvette, below, owned by George Gallant, Sarasota Cafe Racers.
The Corvette ZR1 uses the same aluminum chassis structure as the Z06, above, and incorporates even more carbon fiber body parts, including the roof panel, rocker panels and more. The new 2013 427 Convertible model also uses lightweight carbon fiber in the hood, fenders and floor panels.
Another advanced material found on today’s Corvette is the carbon ceramic brake rotors, above, standard on the ZR1 and available on the Z06. These space-age composite components deliver a significant weight savings over conventional iron brake rotors, while offering exceptional wear resistance.
“Corvette has never been focused on an exclusive material – be it aluminum, carbon fiber, or fiberglass,” said Corvette Executive Chief Engineer Tadge Juechter. “Instead, we are constantly looking for the best materials structure, powertrain, and chassis to improve the performance of Corvette.”
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