SPECIAL REPORT: ENGINEERING THE C8 CORVETTE Inside the design, development and technologies of Chevrolet’s all-new mid-engine supercar

From the editors of SAE's Automotive Engineering

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 CONTENTS

2 Editorial: Realizing Zora’s Dream 20 Inside Tremec’s Supercar DCT To polish the 2020 mid-engine Corvette’s 4 Engineering the 2020 driving prowess, GM and Tremec engineers joined forces to create a new and better Chevrolet Corvette automated transaxle. The eighth-gen (C8) Corvette is a creative mix of novel and traditional technical solutions unleashed at a shockingly low base price. 23 Sweating the Details of C8 Development 10 Long Time Coming How GM’s Corvette engineers tackled After six decades of teasing enthusiasts with challenges in the move to a mid-engine intriguing concepts, Chevrolet has launched architecture. an all-new Corvette with its engine located where Zora intended—behind the driver. 16 More Sting for the Stingray GM Propulsion engineers elevate the evergreen small-block V8 to new heights for its mid-engine Corvette mission.

19 Chevy Reveals 2020 Corvette ON THE COVER Stingray Convertible, An engineering triumph and GM vision finally realized, the 2020 C8.R Racer Chevrolet Corvette Stingray blends state-of-the art vehicle structure, materials and joining technology, chassis design and powertrain integration to create the world's most useful, accessible and affordable supercar. And it's a looker. (Chevrolet)

ENGINEERING THE C8 CORVETTE SPECIAL REPORT SEPTEMBER 2020 1 Realizing Zora’s Dream Don Sherman at home with his recently- purchased 2020 Corvette. The vanity plate’s ‘A-D’ is Arkus- Duntov; its frame denotes Don’s 238-mph land speed record, set at Bonneville in 1986 in a Mazda RX-7 Turbo. The record still stands in 2020.

n my 37 years of covering new-vehicle Porsche, Ferrari or McLaren comes close tested ammunition and assembled development and technology, few to matching the C8’s outstanding mix a Fiberfab Valkyrie GT kit car in the product launches have generated of technology, performance and value. craft shop. This fiberglass-bodied, Ithe high reader interest of the 2020 This Special Report, culled from our steel-framed, V8-powered concoction Corvette Stingray. That’s no surprise. The C8 Corvette coverage in Automotive provided Sherman an early in-depth eighth generation (C8) of GM’s evergreen Engineering magazine and SAE.org, look at the virtues of positioning the sports car finally realizes Corvette highlights the hard work and innovations engine midships, just behind the driver. godfather Zora Arkus-Duntov’s dream of of GM engineers and their supplier After earning his MS degree at a mid-engine architecture. The new layout partners in raising GM’s sports-car Michigan in 1971, Don began an puts 60.6% of vehicle mass over the rear icon to a new level. And for the bulk illustrious 49-year journalism career, tires, compared with the C7’s roughly of that reporting, we thank veteran including two memorable stints at Car 50/50 weight distribution. The resulting autowriter Don Sherman. Besides and Driver. During that period Don’s dynamic performance and overall chassis being the most experienced car- interest in Corvette development led balance have earned praise from road magazine road tester in the business, to an illuminating interview with the testers, racers and owners — more than Don has been hot on the trail of the retired Zora, who revealed his rationale 5,000 of whom have taken delivery paradigm-shifting Corvette for years, for the mid-engine configuration. (as of this writing) in this production- steadily gathering intel on it well before Nearly 30 years later, Zora’s vision delayed, pandemic-wracked model year. the program officially kicked off. has landed in Chevrolet showrooms. With the C8, Corvette executive chief Sherman’s been an SAE member For us, there will be more C8 engineer Tadge Juechter’s team has since 1970. He joined while a University Corvette stories to tell. In the October delivered a rare benchmark: a ~200- of Michigan student, pursuing his Automotive Engineering and at SAE. mph supercar that can sprint from MS in Mech. Eng. After earning his org, we detail how Tenneco and GM standstill to 60 mph (96.5 km/h) in less BS degree at the University of Iowa collaborated on Corvette’s sophisticated than three seconds, offers daily-driver and joining Chrysler’s Institute of “smart” exhaust system. And even utility, long-distance comfort, ample Engineering in 1968, he was drafted hotter C8s are in the pipeline, bringing cargo space, head-turning style, ~30- into the Army. Thanks to Chrysler’s new IC engines and electrification mpg capability on the highway — and efforts, he was assigned to the Yuma, to the ever-evolving supercar.

is priced at $60,000 in base trim. No Arizona, Proving Grounds, where he Lindsay Brooke, Editor-in-Chief SHERMAN CHERYL

2 SEPTEMBER 2020 ENGINEERING THE C8 CORVETTE SPECIAL REPORT SR Continental Ad 0920.qxp 8/12/20 2:45 PM Page 1 CHERYL SHERMAN CHERYL Engineering the 2020 CHEVROLET CORVETTE

The eighth-gen (C8) Corvette is a creative mix of novel and traditional technical solutions unleashed at a shockingly low base price. By Don Sherman Veteran Corvette executive chief engineer Tadge Juechter unveils the long-awaited 2020 C8 in July 2019.

wo days before the 50th anniversary of astronaut There’s an oil reservoir mounted at the top-left corner Neil Armstrong’s leap for mankind and 10 years of the engine and the oil cooler’s capacity is 25% after General Motors emerged from bankruptcy, greater than in C7 for more dependable operation the camouflage was finally ripped from the eighth- during extreme (track or desert driving) conditions. Tgeneration (C8) 2020 Chevrolet Corvette. As widely anticipated, More aggressive valve timing and 11.5:1 compression C8 now flaunts a mid-engine layout that ostensibly puts it on along with new intake and exhaust manifolds raise equal terms with the world’s most venerated supercars. output to an SAE-rated 490-495 hp (365-369-kW) After six decades of experimentation and concept-car teasing, GM at 6450 rpm (with and without the optional low- acknowledged that the new Stingray will enter production before restriction exhaust system). Peak torque is rated year’s end. The truly shocking announcement is a base price of at 465-470 lb-ft (630-637 Nm) at 5150 rpm. The $59,995 including destination, only $3,000 more than today’s front- LT2 is redlined at 6500 rpm. Cylinder deactivation engine C7. Along with moving the cockpit forward 16.5 inches (419 remains to help enhance fuel economy. mm) to facilitate shifting the engine rearward, the new Corvette is Asked what kept GM from clearing the worthy an innovative mix of novel and traditional engineering solutions. 500-horsepower (373-kW) hurdle for the LT2, Jordan Lee, the global chief engineer for small-block engines, New V8 and DCT propulsion acknowledged, “Honesty stopped us at the level we were GM’s new 6.2-L LT2 fifth-generation small-block V8 may have confident could be provided in all of the engines we’ll roots extending back to 1955, but it brings a long list of new features build for the new Corvette. As the only naturally-aspirated to the party. Its aluminum block has revised oiling and venting V8 in the segment, this engine will deliver the visceral arrangements in support of a dry-sump lubrication system with one experience expected of a Corvette,” he told Automotive pressure and three scavenge pumps. The sump casting is shallower Engineering during the car’s unveiling in Tustin, California. to allow mounting the engine 1 in. (25 mm) lower in the car versus Tremec will supply a U.S.-made 8-speed dual-

C7. The crankshaft nose is longer, to power revised accessory drives. clutch automated-manual transmission with paddle GM FECHT/GM STEVE IMAGES: BOTH

4 SEPTEMBER 2020 ENGINEERING THE C8 CORVETTE SPECIAL REPORT Uncloaked view of GM’s new mixed-materials flagship shows extensively- webbed castings serving multiple structural roles, along with various aluminum sheet and extrusions. Note exhaust routing, fan location ahead of rear wheels, More ‘Bedford’ castings in C8’s AL-intensive front structure. Note rear airbox design, and GM-Tenneco electronically-tunable exhaust outlets. bulkhead and A-pillar construction, IP casting and coolant radiator location.

shift control. Along with the absence of a clutch the engine lower in the car. Electronic traction management pedal, a conventional shift lever is also a thing of and limited-slip differential controls are both available. the Corvette’s past. Instead, two console-mounted In addition to previous Weather, Tour, Sport and Track pull toggles select Drive or Reverse while three driving modes, two additional choices have been added to buttons choose either Park, Neutral, or the Low/ C8. MyMode is a configurable setting, and “Z mode” goes Manual modes. Executive chief engineer Tadge beyond MyMode to permit tuning of up to twelve engine, Juechter added, “Regardless of driving mode, our transmission, steering and damper performance variables. performance shift algorithms are so driver-focused they can sense spirited driving and hold lower Thermal-management challenge gears longer for optimum throttle response.” Asked to name the greatest challenge faced during C8 Explaining the loss of the manual transmission development, Juechter doesn’t hesitate to cite the cooling system. selected by 20% of C7 buyers, Juechter noted, “With “With the engine and radiator up front, cooling air entering no interruption of torque delivery during upshifts, the the nose sweeps through the heat exchangers, over the hot DCT is the superior performance solution. Squeezing exhaust manifolds, out the fender wells and side gills, or under a clutch pedal into the foot box and shift linkage the car. That’s straightforward,” he explained. “The solution for down the structural center tunnel would have posed the mid-engine Stingray we validated at 100-degrees F with design compromises we weren’t prepared to make. a pro driver at the wheel is significantly more involved. There And we know our customers will be thrilled with are two radiators in front and a third positioned in the left- the sub-3-second zero-to-60 [mph] acceleration side scoop, which also routes fresh intake air to the engine. we’ve achieved with the Z51 [equipment] option.” “Airflow has to bend abruptly toward the car’s centerline To exploit the benefits of a mid-engine car’s before sweeping past the exhaust headers,” he continued. “Then enhanced traction at the rear wheels, first gear it slams into our huge rear trunk wall. Since there’s no room provides more torque multiplication, while seventh for ductwork, we fitted large air outlet vents, aided by electric and eighth are tall overdrive ratios for quiet and fans, in the rear corners of the car to cool the powertrain during efficient highway cruising. The middle five gear sweltering traffic conditions.” In addition, the cantilevered ratios are closely spaced for optimum acceleration glass hatch has an open “mail slot” at its trailing edge to vent and track performance. Like a race car, the hot air. “The DCT’s substantial cooling needs are satisfied transaxle’s input shaft is positioned below (versus using a lubricant-to-coolant heat exchanger mounted atop

GM FECHT/GM STEVE IMAGES: BOTH above) half-shaft height to facilitate mounting the transaxle and a dedicated flow loop,” Juechter added.

ENGINEERING THE C8 CORVETTE SPECIAL REPORT SEPTEMBER 2020 5 Engineering the 2020 CHEVROLET CORVETTE

Materials mix of the C8 structure. Note the deep center tunnel.

Structure from experience enabled quickening the steering ratio from 16.25:1 Like the C7, the new C8’s structure is a bonded-and- to 15.7:1 to sharpen agility. Michelin will continue welded-aluminum spaceframe built at GM’s Bowling Green, as Corvette’s sole tire supplier. Standard tires

Kentucky, assembly plant. This second-generation design are Pilot Sport ALS (all season) radials while GM IMAGES: BOTH consists of stampings, extrusions, castings, hydroformed Pilot Sport 4S (summer) rubber is included tubes and six intricate die-cast aluminum assemblies aimed with the optional Z51 performance package. at improving torsional rigidity while also reducing the number The 20-in. (508-mm) diameter rear wheels are an of welds. Known as the ‘Bedford Six,’ these structural nodes inch wider than before, while rear tire section width are made at a GM Powertrain plant in Bedford, Indiana. has been increased by 20 mm (0.8-in.) in keeping Thanks to its robust 12-in. (305-mm)-tall center tunnel, with the increased rear-axle loading. Brembo will the new spaceframe is relatively light and claimed to be 10% continue supplying the four-piston fixed caliper, stiffer than before to provide a solid foundation for steering, vented-rotor brake components but no longer delivers suspension and powertrain components. With no need for corner modules to the Bowling Green manufacturing tall, wide rocker sections to supply the desired structural plant. The brake booster is electrically powered. integrity, the C8’s ingress and egress are exemplary. Suspension control arms are cast- and forged-aluminum as New mid-engine packaging before. In place of the fiberglass monoleaf springs long employed Here the C8 bears little resemblance to its in Corvettes, C8 has conventional coil springs encircling a immediate predecessor. Except for a 2-in. (51-mm) damper at each wheel location. GM’s optional Magnetic Ride loss of hip room, occupant space is unchanged. Control, which senses wheel motion and automatically adjusts Rearward seat travel is an inch longer and the the dampers using BWI’s magneto-rheologic technology, backrest recline angle is nearly doubled to better has been retuned for improved ride and handling. accommodate taller occupants. In spite of a more “No Corvette has ever felt so comfortable, nimble, and stable,” steeply angled hood and low cowl height, there’s Juechter exclaimed. “We’re confident our customers will admire space available in the front cargo compartment the strides we’ve achieved in ride quality. And now that the for a carry-on suitcase and a briefcase. car’s center of gravity is very close to the occupants’ hip points, The rear trunk will swallow two sets of golf the feeling during acceleration and braking is analogous to bags or the standard removable roof panel. An riding at the center—instead of the ends—of a teeter-totter. entertaining view of the well-dressed LT2 V8 is There’s practically no sense of pitch motion in the cockpit.” available through the hatch glass, which has an Moving the engine rearward also cleared a path for a straighter, unsealed trailing edge to vent heat. Key dimensions stiffer connection between the steering wheel and the electrically- are larger: 0.5-in. (12.7-mm) of increased wheelbase;

assisted rack-and-pinion gear. Less weight on the front wheels 5.4-in. (137-mm) longer overall length; 2.2-in. (55.9- GM IMAGES: BOTH

6 SEPTEMBER 2020 ENGINEERING THE C8 CORVETTE SPECIAL REPORT mm) more width and a 1.4-in. (35.5-mm) wider front track. Height is reduced by 0.2-in. (5 mm). Curb weight is inconveniently increased by roughly 200 lb. (90.7 kg) versus C7’s base weight. Program engineering manager Josh Holden explains why: “While we spent more on weight-saving measures, there is significant added equipment in the base C8: the automatic transmission and dry-sump lubrication system for example. The substantial spaceframe anchor points for the coil springs, larger rear tires and wheels and a more- complex cooling system also increase mass.”

The skin – and underneath it Two key C7 body-systems suppliers return to C8. According to GM engineers, Continental Structural Plastics supplies the primary molded-SMC exterior panels, while the car’s triangular engine-bay trim panels are sourced from Plasan Carbon Composites (see sidebar). The exterior fascias, in TPO, are from Magna, as Dry-sump LT2 carries its lubricant in the black tank shown at right. Note ignition coils moved from top of rocker covers to new location low on block, underneath is the Stingray’s removable roof panel. The rear bumper the exhaust ports. beam is a carbon-fiber pultrusion to save weight. A large front air splitter, in collaboration with a combination spoiler and airfoil on the rear deck, contribute 400 lb. Inside, attention to detail is evident in the standard leather seat (181 kg) of downforce at speed. Relocating the exhaust and dash trim adorned with contrasting color stitching. Instead of outlets to the rear corners of the car clears space for a molded plastic door and console surfaces, aluminum or genuine

BOTH IMAGES: GM IMAGES: BOTH trunk capable of stowing the roof panel or two golf bags. carbon-fiber panels are fitted. Speaker grilles are stainless steel.

Plasan’s classy carbon fiber The new Stingray’s engine compartment PCC is well versed in the art of take a lot more than that.” Murch has high brims with visual delight. Its centerpiece, of lightweight, functional aesthetics for praise for Chris Basela, who as the BFO (global course, is the mighty LT2, but equally Corvettes. The Walker, Michigan-based bill-of-material family owner) for carbon fiber fetching are the two pieces of “eye candy” company supplied the exposed-weave hood components at GM, served as PCC’s interface flanking the V8: beautiful carbon-fiber trim and roof panel for the sixth-generation ZR-1 on the program. “Chris was key in working with panels supplied by Plasan Carbon and reprised it on the base and Z06 C7 by us and with the engineering team at GM to Composites (PCC). The triangular panels’ adding CFRP rockers and splitters. ensure that the proper robustness was applied deep gloss and exposed-weave design are as The C8’s panels “are constructed from the to those components,” Murch said. likely to draw a crowd as the 495-hp heart same family of carbon-fiber epoxies that we’ve The PCC development team took a beating between them. worked with on past Class-A woven traditional approach in using one-sided steel “Class-A was GM’s goal with those parts,” cosmetics,” Murch told AE. “The twist to these autoclave tooling, with manual lay-up explained Robert Murch, R&D principle is there is a bit more temperature requirements “primarily due to the detail that goes into engineer at PCC. “And while we’re not in the due to their [engine compartment] location. these components,” Murch explained. “Each styling business, we are in the business of We had to meet a minimal 150C thermal ply is hand placed into the tool, with careful making the stylist’s dreams come true.” requirement, but we know the material can consideration to the processes to ensure proper grain direction of the weave—it’s an opposing pattern from left-hand to right- hand sides on those covers. That’s GM’s intention that we match that appearance part to part.” Nest tooling allows the panels for each Corvette to be molded in vehicle pairs. “In each generation of Corvette, GM has upped the ante of where they want to put carbon-fiber material,” Murch noted. “To date, these [the C8 panels] are the most challenging and rewarding at the same time.” Lindsay Brooke BOTH IMAGES: GM IMAGES: BOTH

ENGINEERING THE C8 CORVETTE SPECIAL REPORT SEPTEMBER 2020 7 Engineering the 2020 CHEVROLET CORVETTE

Extensive CFD and wind-tunnel work optimized the mid-engine Corvette’s aerodynamics and thermal management.

unprecedented 12 exterior colors. The options list includes a wireless phone charger, 14-speaker Bose audio system and a high-definition performance data recorder. One thoughtful feature is a traditional round volume knob on the center console’s touchscreen.

More engineering highlights GM’s new Global B electrical architecture provides quicker subsystem communication, fewer wires, enhanced display screen resolution, greater security measures and the ability to update the Corvette’s software over the air via WiFi. The low-profile headlamps are lit by projector beams and the taillamps are LED. For the first time, Bowling Green will manufacture Corvettes with right-hand drive to better serve foreign markets. A new proprietary glass- reinforced resin material trims weight from the instrument panel and trunk moldings. To reduce the likelihood of scraping the car’s chin over driveway A look inside the new Tremec 8-speed DCT. The transaxle’s input shaft is verges, an optional lift system increases front positioned as on a racecar, below half-shaft height to facilitate mounting the ground clearance by 40 mm (1.6 in.) in 2.8 s. That engine lower in the car. equipment can be programmed using GPS data to remember thousands of raise-the-chin locations. Vertically-oriented vents and climate controls help reduce the height Considering the revolutionary design, engineering of the instrument panel, enhancing the feeling of spaciousness. and development invested in C8, it’s evident why C8’s small-diameter, two-spoke steering wheel is flattened top this latest Corvette was a long time coming. Now and bottom to avoid obscuring the view of the 12-in. (305-mm) that this Ferrari-for-working-stiffs is here, the reconfigurable instrument cluster. There are three seat choices to anticipation will begin concerning more powerful balance comfort and support under aggressive (racetrack) driving editions, a potential Cadillac-branded version of conditions, six interior colors, two optional upholstery stitch choices the Stingray and how electrification might stretch

and six seatbelt colors. Add to that two wheel designs and an Corvette’s appeal into unexplored territory. GM IMAGES: BOTH

8 SEPTEMBER 2020 ENGINEERING THE C8 CORVETTE SPECIAL REPORT BOTH IMAGES: GM SR TennecoAd0920.qxp8/26/204:44PMPage1 We’reYour Sound Orchestrating Unique Learn more at tenneco.com. near-zero with sound and balance of performance perfect emissions. the for test the to expertise emission and acoustic our Put modes. acoustic performance in ofsupport the driver-controlled and sport track that achieve controlled valves andelectronically flow mixing muffler of combination a through accomplished is sound unique Corvette’s Long time coming

Aerovette was perhaps the most exquisite of all mid-engine Corvette concepts—and Zora’s favorite.

After six decades of teasing enthusiasts with intriguing concepts, Chevrolet is launching an all-new Corvette with its engine located where Zora intended— behind the driver. By Don Sherman

n the Spring of 1957, while pondering the demise Superior vehicle dynamics of Chevrolet’s Corvette Super Sports racer at Arkus-Duntov, born in Belgium in 1909 to Russian parents, Sebring’s 12-hour endurance race, legendary earned a mechanical engineering degree at the Charlottenburg ICorvette godfather Zora Arkus-Duntov concluded, Technical University (now the Technical University of Berlin), in “Heat source must be behind driver.” The official 1934. In his teens, he graduated from two to four wheels as his explanation offered for dropping out after 29 laps preferred means of rapid transport. In 1941, after relocating to was a failed rear-suspension bushing—but the actual the U.S., he adopted the surname Arkus-Duntov out of respect show-stopper was that driver John Fitch’s feet were for his father and step-father, both of whom shared a home being cooked by the exhaust-header pipes snaking with his mother and brother Yura in Leningrad, Russia. around the SS’s sheet magnesium ‘firewall.’ Arkus-Duntov’s fascination with speed made him practically an Sixty-two years later, the Corvette development eyewitness to Adolf Rosenberger’s 1924-25 racing victories with the trek initiated by Arkus-Duntov’s brainstorm reached mid-engine Benz Tropfenwagen. The next decade, the fearsome V16 New York’s Times Square, when a camouflaged mid-engine Auto Union cars conceived by Dr. Porsche’s budding prototype (see cover image) driven by chief engineer design office often trumped Mercedes’ traditional front-engined Tadge Juechter and with GM CEO Mary Barra as Grand Prix racers. In the year of Arkus-Duntov’s epiphany (1957), passenger, finally confirmed that the 2020 Corvette F1 driver Jack Brabham’s mid-engine Cooper showed promise at will have its engine located behind the driver. the Monaco Grand Prix. Two years later, the Cooper team won the The 7-18-2019 date prominently displayed on both World Championship, rendering front-engined racecars obsolete. sides of the prototype car is when GM will reveal His engineering education gave Arkus-Duntov a clear details about the mid-engined Corvette, exactly fifty understanding of the physics underlying mid-engine car design. years after the Apollo 11 mission to the Moon. Until This is the preferred configuration for rear-driven sports cars and then, we have but history and speculation—supported all race cars (rules permitting) for the following reasons: Traction by interviews with five Corvette chief engineers and while accelerating from rest and exiting turns is maximized with one retired GM vice chairman—defining the signposts the engine located as closely as possible to the drive wheels.

and sidetracks leading to the revolutionary Corvette. The load transferred forward during aggressive braking helps ARCHIVES GM HISTORICAL ARCHIVES GM HISTORICAL IMAGES: BOTH

10 SEPTEMBER 2020 ENGINEERING THE C8 CORVETTE SPECIAL REPORT Corvair Monza GT concept of 1962 used a mid-mounted flat six.

all four tires produce nearly equal stopping forces. A central- mounted engine also minimizes the vehicle’s polar moment of inertia about its vertical axis; as a result, initiating and arresting yaw motion (turning) is easier with the engine in the middle. Bottom line: Mid-engine cars deliver quicker acceleration, superior braking and more agile handling. Arkus-Duntov joined Chevrolet R&D in 1953. When a rear- Zora Arkus-Duntov: his mid-engine focus was influenced by Auto Union’s pre-WWII Grand Prix cars. mounted transaxle was under consideration for GM’s 1960 mainstream models—beyond those used in the Corvair and compact Pontiac Tempest—he realized that this component Ferrari adopted a version of GM’s creation for might enable a mid-engined, second-generation Corvette. Design its 2011 FF GT (now called the GTC4Lusso). studies revealed that the driver’s forward visibility and the car’s Alas, GM’s management chose to support center of gravity would both benefit from moving the engine Chaparral Cars in the Can Am race series instead rearward. Unfortunately, problems with the transaxle resulted of assaulting Ford at the 24 Hours of LeMans, so in its cancellation and the mid-engine C2 was stillborn. CERV II was also shelved. It too slipped from GM’s The consolation prize was approval to build an experimental grasp, selling at a 2013 auction for $1.1 million. single-seater with Indy 500 potential, the first of thirteen GM mid- engine concept and show cars. Dubbed a Chevrolet Engineering Tantalizing concepts Research Vehicle (CERV), this 1960 concoction had a 500-hp (373- After Ford finally won LeMans in 1966, GM’s kW) small-block V8 yielding a top speed over 200 mph (322 km/h) Design and R&D departments teamed up to build at the Milford Proving Grounds. Its independent rear suspension the stunning Astro II mid-engine concept for the made the leap to the 1963 Sting Ray (C2) production model. following year’s New York auto show. Road & Track’s When GM politics forbade Arkus-Duntov to go racing, CERV was cover coyly queried, “A Chaparral for Production?” ‘loaned’ to a west-coast museum for display. Retrieving this stunning Still lacking a suitable transaxle, GM answered ‘no.’ heirloom ended up costing GM $1.32 million at a 2017 auction. R&T again swallowed the bait two years later GM Design boss Bill Mitchell joined the mid-engine game when another GM prototype stole the New York in 1962 with the Corvair Monza GT coupe, constructed with show, exclaiming, “We’ll stake our reputation on the production model’s flat-six engine relocated from behind this being the Corvette of the future.” Called simply the rear axle to the middle of the car. Driver and passenger a Corvette Prototype (internal code XP-882), this climbed aboard by hinging the unified doors and windshield mid-engine mirage combined a transverse small- assembly up and forward in one dramatic sweep. block V8 with an Oldsmobile Toronado transaxle Responding to Ford’s ambitious GT40 international endurance to drive both axles. The Ford Pantera, Mercedes- racing effort, Arkus-Duntov yanked another experiment out of his Benz C111 and AMC AMX/3 ironically all seconded sleeve. The 1963 CERV II had a centrally mounted 7.0-L big-block the mid-engine motion at the same show. Arkus- V8 with a transmission at each end of its crankshaft to provide Duntov was ready to serve this car to the Corvette four-wheel drive. Top speed climbed to 214 mph (344 km/h) in faithful—but when Chevy boss John DeLorean

GM HISTORICAL ARCHIVES GM HISTORICAL ARCHIVES GM HISTORICAL IMAGES: BOTH testing. Finding favor with this twin-transmission arrangement, denied that wish, he threatened to resign.

ENGINEERING THE C8 CORVETTE SPECIAL REPORT SEPTEMBER 2020 11 Long time coming

CERV II: midship V8, two transmissions, four-wheel drive. Astro II concept from 1966: still no suitable transaxle.

Mitchell’s next move was the 1969 Holden spot-welded-and-adhesively-bonded structure was deemed Hurricane concept car, constructed in Australia prohibitively expensive for production. Result: another dead end. with a mid-mounted 253 cu. in. (4.1-L) V8 Most Corvette aficionados consider the most tantalizing mid-engine driving the rear wheels through an experimental experiments to be the high visibility part of GM’s ill-fated rotary- engine transaxle. Mimicking the Monza GT, this two- gambit. The XP-987 GT bowed at the 1973 Frankfurt motor show with GM- seater’s canopy was lifted by servo motors for designed, Pininfarina-crafted coachwork over a Porsche 914 chassis and an entry. Advanced features included one of the first experimental two-rotor engine in the middle. At the Paris salon later that back-up cameras and oil-cooled disc brakes. year, Arkus-Duntov pulled out the stops with his awesome Four Rotor: two The next stage of XP-882 development was a rotaries in series, under a stunning body fitted with folding gullwing doors. thorough redesign in collaboration with Reynolds When GM’s rotary engine work ceased soon thereafter, a Metals to shed weight. The new aluminum conventional V8 was transplanted under deck and the car was unibody trimmed 500 pounds (227 kg) for the rechristened Aerovette. After he retired, Arkus-Duntov told anyone

1972 prototype code-named XP-895, but its who’d listen that this was his all-time favorite mid-engine design. ARCHIVES GM HISTORICAL IMAGES: BOTH

Gib is the Engineer’s engineer He was known as Zora’s problem-solver “Zora would ask me to • (Optional) shaft forward and kindred spirit, and now Gibson “Gib” sketch layouts, initially with from bevel gear to front-axle Hufstader is delighted to see Arkus-Duntov’s the Hewland transaxle, then final drive differential. mid-engine dream hit the streets. with other arrangements to Hufstader’s most Hufstader, 88, became an SAE member in reduce length,” Gib recalls. memorable project was the 1957, the year he joined General Motors R&D “A transverse layout using Four-Rotor Corvette following studies at the General Motors Institute parts of an Oldsmobile constructed for the 1973 Paris (now Kettering University) and military service Toronado automatic Salon. “While that three- at the Army’s Aberdeen Proving Grounds. transmission with all-wheel month effort didn’t venture During his 45-year GM career, Hufstader drive capability earned Zora beyond the show car,” he earned seven patents for driveline-related a patent in 1971.” The noted, “it had ample potential innovations. His passion for motorsports born patented mid-engine Gib Hufstader in 2019. for further development.” in 1959 persists. In the 1960s, he assisted powertrain layout works as Today, Gib’s hobby fleet Corvette and Camaro teams, including Roger follows: consists of the ’67 427 Corvette he campaigns Penske’s, in both endurance and Trans-Am • Engine transversely positioned behind in vintage road racing, an aerobatic Steen’s events. Co-driving the Owens-Corning cockpit with west-east orientation. Skybolt biplane, and eight motorcycles— Corvette at the 1969 12 Hours of Sebring, he • Crank-mounted torque converter drives including a 1952 Vincent Black Shadow, a 1974 scored second in the GT class and 14th overall. transverse automatic transmission located Ducati 750 Super Sport and a 1956 Triumph Hufstader joined the Corvette group in 1964. ahead of engine via Morse chain. 650 Trophy. Look up ‘engineer’s engineer’ in During that time, efforts to engineer a viable • Bevel-gear box at transmission’s output the dictionary and you’ll see Gib Hufstader, mid-engine production design persevered at end drives shaft passing through engine oil wearing an engaging smile.

what he describes as the ‘hobby’ level. pan to rear axle final drive differential. D.S. BROOKE LINDSAY ALL IMAGES: GM HISTORICAL ARCHIVES GM HISTORICAL ALL IMAGES:

12 SEPTEMBER 2020 ENGINEERING THE C8 CORVETTE SPECIAL REPORT XP-987 with its two-rotor rotary engine previewed GM’s stillborn Wankel future. The XP-895 concept featured a Reynolds Aluminum body.

at the 2002 Detroit auto show. Key features were Corvette Prototype XP-882: a magnificent exterior shape inspired by the F-22 transverse-mounted V8 with Olds Toronado automatic Raptor fighter aircraft, scissors-hinged doors, a transmission. chassis made of Aerogel composite and a 7.5-L 750-hp (559-kW) V12 with direct fuel injection and cylinder deactivation. In the 2003 through 2009 model years, Cadillac leveraged the Corvette C5 and C6 platforms for its XLR luxury roadster. For Cadillac fans, hope springs eternal that the brand will again offer a two-seater—this time a BEV with a mid-mounted motor. Our circumstantial evidence is that a new two-seat Cadillac sportscar design was wind-tunnel tested a few years ago. McLellan’s successor Dave Hill, who coincidentally

BOTH IMAGES: GM HISTORICAL ARCHIVES GM HISTORICAL IMAGES: BOTH came from Cadillac, focused on ridding Corvettes of quality flaws, especially squeaks and rattles. He was tempted to use Cadillac’s Northstar DOHC V8 but found it too bulky. Instead, the 2006 2009: ‘The patient is dead’ C6 Z06 he created brought 505 hp (377 kW) When he left the building in 1975, Arkus-Duntov’s parting and 7,000 rpm to the party with a 7.0-L OHV words to his successor were “Dave (McLellan), you must build small block at the front atop an aluminum space the mid-engine Corvette.” That wouldn’t happen in the 20th frame. In 1993, Hill hired Tadge Juechter as his century, though there was sufficient interest in the layout to create assistant, whom he describes as “a wonderful another ambitious experimental called CERV III (also Corvette engineer, team leader, and GM executive.” Indy). This 1986 GM design study was modeled in Italy and Tom Wallace succeeded Hill as Corvette chief built in England by Lotus with electronic features galore. Active engineer in 2005. After the redoubtable 2009 suspension, four-wheel steering, drive-by-wire and advanced Corvette ZR1 was bumped to 638 hp (476 kW) navigation gear were packed into a molded-composite chassis. with an Eaton supercharger and intercoolers, the The 4.3-L V8 was initially a version of the engine supplied to inevitable, ‘what’s next?’ question was asked. Indycar racers. In 1990, that power source was supplanted by a It was answered with ‘mid-engine’ as the most twin-turbo version of the Lotus-designed LT5 5.7-L DOHC V8. practical means of improving performance. Acknowledging the benefits of moving mass rearward, McLellan Juechter was the first hand-raiser, and Wallace did shift the transmission aft for the comprehensively redesigned quickly seconded the mid-engine motion, in part 1997 fifth generation (C5) Corvette, introduced shortly after Arkus- because of his years of amateur road racing. Duntov’s passing at 86 on April 21, 1996. Like the original CERV, Chevrolet’s marketing department, realizing C5’s manual and automatic transmissions were located just ahead this might be an excellent means of attracting of the differential, where they remained through today’s C7. younger buyers, also was enthusiastically on board. GM vice chairman Bob Lutz was

LINDSAY BROOKE LINDSAY The most recent official ray of hope that Arkus-Duntov’s mid-

ALL IMAGES: GM HISTORICAL ARCHIVES GM HISTORICAL ALL IMAGES: engine dream was not dead was Cadillac’s Cien concept shown skeptical at first, but he was soon convinced.

ENGINEERING THE C8 CORVETTE SPECIAL REPORT SEPTEMBER 2020 13 Long time coming

CERV III experimented with composite chassis, advanced electronics.

The engineering team then satisfied CEO Rick Wagoner that a mid-engine Corvette would earn a return on investment with a modest price bump over the then-$47,895 base model. Unfortunately, cash and time ran out before the mid-engine cause advanced beyond full-size clay models and test drives in reference Porsches and Ferraris. In October 2008, boss Lutz returned from a board meeting to report, “The patient is dead. No new Corvette capitalization is available and I don’t know the foreseeable future.” The following year, Wallace took early retirement at age 62 to avoid placing Corvettes on life support with new decals and color schemes. Succeeding Zora as Corvette chief engineers from 1975 to 2008 were Dave McLellan (center), Dave Hill (left) and Tom Wallace. Mid-engine debut On June 1, 2009, GM filed for Chapter 11 bankruptcy. 800 hp (596 kW). “ZERV” and “ZORA” nameplates have been Juechter, as the last Corvette engineering chief copyrighted by GM along with various reactive aerodynamic devices. standing, continued working on a seventh-generation Three removable targa roof designs will be offered at launch car for a 2014 model year introduction. Since this and a convertible will follow later. C8’s foundation will be a was hardly the opportune time to launch a flashy hydroformed aluminum space frame as before, with composite Corvette with a revolutionary powertrain layout, body panels supplied by Plasan and others. Expect a shift to Juechter kept team heads down. They focused rear coil springs (away from today’s transverse composite leaf on launching well-received Z06, Grand Sport springs) along with 245/35ZR-19 front tires and 305/30ZR- and the recent 755-hp (563-kW) ZR1 editions 20 rear rubber by Michelin. As before, Brembo will supply while, behind the scenes, work intensified on the conventional and carbon-ceramic brake components. mid-engine C8 due for the 2020 model year. The announced June 28 auction for charity of the final C7 Corvette Pre-July 18 speculation calls for a base LT2 6.2-L suggests that the previously expected generational overlap will small-block V8 producing more than 500 hp/373 not happen. Production of C8s for publicity and engineering use kW (up from C7’s 455 hp). An 8-speed dual-clutch, is underway at GM’s Bowling Green, Kentucky, assembly plant paddle-shifted automatic supplied by Tremec and and customer deliveries are expected to commence well before Fassler will be the sole transmission. Later in C8’s the end of 2019. Expect an attractive base price to maintain life, hotter LT-series V8s will be introduced, some Corvette’s longstanding value proposition, with subsequent with flat-plane crankshafts, others with DOHC. A six-figure future editions capable of slaying hypercars wearing

top-spec twin-turbo V8 will eventually deliver over Bugatti, McLaren, Ferrari, Lamborghini, and Porsche badges. MUSEUM CORVETTE ARCHIVES; NATIONAL GM HISTORICAL FROM TOP:

14 SEPTEMBER 2020 ENGINEERING THE C8 CORVETTE SPECIAL REPORT FROM TOP: GM HISTORICAL ARCHIVES; NATIONAL CORVETTE MUSEUM AVE SAE2Ad1117.qxp_Layout110/27/171:05PMPage P17172963 THE FEATURES YOUR PEERSREQUESTED PLATFORM TECHNICAL RESOURCE eBooks, magazines, and more. eBooks, discover, of and share SAE’s more than 226,000 current andtechnical historical papers, standards, isyour destinationSAE MOBILUS™ for resources mobility engineering with access instant to explore, the future ofmobilityengineering Your criticaladvantage to develop SAE MOBILUS informed informed subscription decisions to enable data usage content timely with accurate, administrators provides 4reporting COUNTER you download before resource the preview can you so snippets with content results focused returns intuitive site search Improved, process manual atedious eliminating standards, for tracking revision represents visually redlining Dynamic creation folder custom and annotations, document personal searches, saved by allowing accessible materials pertinent keeps dashboard customizable The industry. mobility the facing problems essential solving on focus can students and engineers so navigation and MOBILUS SAE the feedback, user with extensive Developed platform features intuitive, easy search search easy intuitive, features
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saemobilus.org I STINGRAY rpm redline). That includesflat-out drivingconditions with to assure reliable oilingacross thefulloperating range (6600 optimum performance, drysumplubrication isstandard equipment. facilitate mounting theengineaslow aspossible inthechassis for features related to Corvette’s move to mid-enginearchitecture. To mm) bore spacing,theLT2 cylinder caseisafresh designwithkey Cylinder block LT2 ingeniouslyblendsinnovation withtraditional designfeatures. refining (andnever givingupon)abrilliant original design. per-dollar quotient. It’s thepayoff for 65 years ofcontinuously key metrics: billofmaterial, package efficiency, andthepower- valves percylinder, remains unmatched versus itsrivals inthree competitive fuelefficiency compared withtheoutgoing C7. (the most yet inthebaseStingray), stirring response, and Chevy’s all-new, eighth-generation 2020 Corvette more power supplied by BASF. Ultramid dry-sump oilreservoir at upperright, ignition coil location andblackreinforced nylon through continuous development. Note new 2020 Stingray ismore efficient andpowerful GM’s latest LT2 small-blockV8powering the 16 SEPTEMBER 2020 new-for-2020 V8.Known astheLT2, the6.2-L V8gives engineer Jordan Lee leveraged past success to create a out thewindow, GMPropulsion engineers ledby chief nstead ofheaving decadesofsmall-blockV8expertise Lubrication andventilation systems are thoroughly revised While itcontinues thesmall-block’s classic 4.40-inch (111.8- While the eighth-generation Corvette isrevolutionary inscope, its And thesmall-block,withitssinglecamshaftinblockandtwo More sting for the thicknesses. Two distinct bays collect oildraining aluminum diecasting with3.5-mm(0.13-in) wall Block bottom cover mm) deckheight are carriedover from theLT1 V8. bore, 3.622-in (92.0-mm) stroke, and 9.24-in (234.7- the eight ignitioncoils. The 4.065-in (103.25-mm) engine mount bosses andattachment points for crankshaft. The block’s flanksfeature new ribbing, nodular-iron mainbearingcapsto helpsecure the as before, withcast-iron bore liners andcross-bolted reservoir mounted to theleftfront corner oftheengine. returning itto the7.5-quart (7-L) injection-molded camshaft viachain,scavenges oilfrom thevalley, a mist ofoildroplets. Agerotor pump, driven by the and windagelosses causedby thecrank whirlingin diminishes aeration ofthelubricant by thecrankshaft all-time first, Automotive Engineering believes) greatly at itsbottom. According to Lee, thisarrangement (an compartment between thecylinder banksissealed and valve lifters into thecrankcase, theLT2’s valley while loadedto 1.2-g inallthree directions. ambient temperatures upto 100-deg.F, and The low-profile bottom ‘pan’ isahigh-pressure The new deepskirtblockisA319-T7 cast aluminum, To prevent oilfrom draining from thecylinder heads ENGINEERING THEC8CORVETTE SPECIAL REPORT engine Corvette mission. heights for itsmid- small-block V8to new elevate theevergreen GM Propulsion engineers by DonSherman

ALL IMAGES: GM ALL IMAGES: GM SPECIAL REPORT ENGINEERING THEC8CORVETTE SPECIAL of mass andreduces thecost ofeachoilchange. compared withthe LT1. That trims 3.7-lb (1.7-kg) facilitates a2.2-quart reduction oftheV8’s oilsupply, enhances thenew lubrication system’s reliability and synthetic oilisinuseat redline. Lee claimsthisgreatly In theLT2, less thanonequartofthe Dexos 20W40 likelihood ofmomentary pressure pumpstarvation. harsh operating circumstances, increasing the lubricating oilcanbetrapped intheengine during manifold sonooilvapor escapesto atmosphere. covers whichare inturnplumbedto theintake lines runfrom thereservoir to thecylinder-head losses below the5,500-rpmswitching point. Vent and highlubrication outputsto minimize parasitic explained. Acrank-driven vane pumpprovides low and flow losses inherent to external lines,Lee directly to theenginetrimsmass, complexity, the inboundoilandvapor. Attaching thereservoir Ultramid. Italsohandlescentrifugal separation of BASF,by is30%glass-filled PA66+PA6, known as 14.6-in x7.7-in) plastic dry-sump oiltank,supplied Lubrication andventilation mounting boss isintegral withthiscomponent. cooling capacity thantheLT1’s oilcooler. The oilfilter side oftheoilsumpisrated at 23kW, 28%greater external oil-to-coolant heat exchanger bolted to the oil clingingto thecrankshaft counterweights. An gerotor pump. Amoldedplastic scraper peels bearings; eachbay isscavenged by acrank-driven from piston-cooling jets andthecrankshaft andcam In theLT1 V8,upto three quarts(2.8L) of The LT2’s 450-mm x370-mm x195-mm (17.7-in x A new, more aggressive camshaftdesignand a phaserwithgreater authority conspire to increase theLT2’s volumetric efficiency.

Lash Adjusted Valve Lift (mm) 1000 1200 1400 000 200 400 600 800 cover textured to coordinate withtheCorvette’s rear bodysurfaces. particularly attractive, designers hiditbeneath amoldedplastic diameter astheLT1’s. Since the blackplastic intake manifold isn’t throttle body, now aimedtoward therear ofthecar, isthesame eight runners are 210mm(8.27-in) long.The 87-mm (3.42-inch) friction process that temporarily meltsmating surfaces. The molded PA66. These pieces are welded together usingavibratory intake provides eight runners allofwhichare 210mminlength. and two 185-mmrunners (due to space limitations), thenew LT2 view oftheroad ahead.While theLT1 hadsix225-mm-longrunners runners—because there’s noriskoftheengineblockingdriver’s internal volume increased from 13.5-to 16.0 Landmore efficient (76-mm) ofheight available for alarger intake plenum—with its engineer Lee acknowledges that there’s nearlythree more inches and flexibility inthedesignofintake andexhaust systems. Chief Intake, exhaust andTenneco downstream lowest possible enginemounting andcenter ofgravity. transaxle’s inputshaftbelow itsoutputshaftsto facilitate the transmission. Extra effort was invested inlocating thenew or torque converter isrequired withthenew automatic fuel-saving Active Fuel Management four-cylinder operating mode. diminishes torsional vibration, aconcern whileswitching to theLT2’s the crankshaft to thedual-clutch automatic transaxle. This device rubber belts.Asecond damperat therear oftheengineconnects ring equippedwitharibbedouter surface to drive accessories via oil pumps.The front damperhasanaluminumhub andsteel inertial crankshaft vs. theLT1. Alongernoseextension drives thethree stacked Crankshaft -330 -300-270-240-210180-150-120 -90-60-300 306090120150180 210240270 300330 The intake manifold consists offour ‘shells’ madeofinjection A key advantage withthemid-engine layout ismore space The rear damperissmallindiameter becausenoflywheel A switch to S38alloy steel improves thestrength oftheLT2’s forged Lash Adjusted Valve Liftvs.Crank Angle Crank Angle (crankdeg) SEPTEMBER 2020 17 STINGRAY degrees ofcam phasingauthority andGM’s AFM cylinder (365/369 kW; a30/35 hpgain over theLT1) arrives at 6450 rpm. attained at 5150 rpm.The SAE J1349-certified 490/495 hppeak N-m, with/without theoptionalperformance exhaust system) is both above 5000rpm.Claimedpeaktorque of465/470 lb-ft(637 the mid-range (2800—4500 rpm),there are significant gainsin 4-deg. While thesechangessacrificed somepower andtorque in the LT1’s exhaust-valve timing.Intake duration was increased by mm (0.55-in) andduration was uppedasignificant 18-deg.over Exhaust valve liftwas increased from 13.5-mm(0.53-in) to 14.0- volumetric efficiency withamore aggressive camshaftdesign. volume. The ceramic bricksare drilledfor O2sensorclearance. 132.1-mm indiameter x140.0-mm Lofinternal long,yielding1.9 a single-volume, close-coupled catalyst perside. Eachcat is runners, abrass-colored hue, andgently tapered collectors feeding exhaust headers. The classic four-into-one layout hastubular perfect therouting andsurface finishoftheLT2’s stainless-steel 18 SEPTEMBER 2020 2014. which debuted in the LT1 (shown), carried over from ratio are essentially and compression cylinder heads The new V8’s The LT1’s variable valve timingsystem providing upto 62 Lee’s engineeringteam took fulladvantage ofthenewfound GM designers alsocollaborated withpowertrain engineers to More sting for the The Corvette V8’s SAE J1349-certified 495 hppeakrepresents a35-hp gain over theLT1. volume withthecar'sSportandTrack drivingmodes. controlled mufflingsystem that switches tone and engineers helpedtheC8team create anelectronically- exhaust note. Reprising theirwork onC7, Tenneco Engine control isviaGM’s 32-bit E99ECU. interests ofcruisingserenity andfuelefficiency. deactivation system bothcarryover inthe for thenew Corvette is slated at 170 engines/day. small-block production units/day. is2,200 LT2 output record building8,832 enginesinoneday, current its 1955 inception. While theplant established aworld Tonawanda hasbeenthesmall-blockV8’s homesince machining centers inlieuoftransfer lines.Builtin1937, NY, engine plant usingcontemporary CNCflexible Manufacturing subjected to asimulated ginevery 1.2 direction. system was capableofmaintaining pressure when Pontiac technical center verified that thelubrication banked oval. Tilt-stand tests inGMPropulsion’s the Papenburg (Germany) (7.6-mile) 12.3-km Nordschliefe, Virginia International Raceway, and (Michigan) Road Course, theNurburgring’s grueling required countless lapsaround theMilford Engine testing operating at 2,175 psi(15Mpa)maximumpressure. the LT1, thenew LT2 employs direct fuelinjection, exhaust), and11.5:1 compression ratio carryover. Like mm intake, 1.59 in/40.4 mm for thesodium-filled combustion chambers, valve sizes (2.13 in/54 unchanged from theLT1 designs.The 59-cc Cylinder heads Owners andbystanders willrevel inC8'ssonorous The LT2 ismanufactured at GM’s Tonawanda, Proving the new Corvette’s speedandstamina Cast inA319-T7, thesecomponents are largely ENGINEERING THEC8CORVETTE SPECIAL REPORT

BOTH IMAGES: GM

BOTH IMAGES: CHEVROLET BOTH IMAGES: GM

BOTH IMAGES: CHEVROLET R Stingray convertible, C8.Rracer Chevy reveals 2020 Corvette SPECIAL REPORT ENGINEERING THEC8CORVETTE SPECIAL resembles aconventional trunk. rear-opening section that more closely covering theengineissolid,witha pronounced buttresses. The bodywork of glass behindthedriver flanked by glass cover, butusesanupright section view. The convertible doeswithoutthis the coupe that exposes theengineto giveaway istheglass rear hatch on coupe, even withtheroof open.The distinguish from thestandard Stingray Corvette convertible willbedifficultto engine. From someanglesthenew and stores above the rear-mounted center roof section folds intwo pieces folding-hardtop designinwhichthe Corvette Stingray convertible usesa is nofabric to beseen:the2020 for itsaggressive $59,995 baseprice. coupe, whichwas widelycelebrated $7,500 more thanthe2020 Stingray base price started at $67,495 —just the Corvette Stingray convertible's production inthefirst quarter of2020, driving experience. When itwent into Corvette butalsoseekinganopen-top enthusiasts considering thenew called ita“no-loseproposition” for and comparatively affordable price, no-compromisescar’s performance Tadge Juechter, underscoring the October 2019. Executive chiefengineer Corvette Stingray inCape Canaveral in all-new, mid-engine-layout 2020 Although calledaconvertible, there convertible version ofits Chevrolet unveiled the association withastronauts, einforcing theCorvette’s long the race cardebuted at the Rolex 24 at Daytona in January2020. The 2020 Corvette C8.Rcompetes intheGTLM series; removable roof section. Holdersaidspring was designedto incorporate itsown noted that theconventional Stingray for thestandard Corvette structure: he there isnoadditionalstiffening required the conventional 2020 Stingray, but approximately 77lb(35 kg) heavier than that theStingray convertible is massBalancing vs. airflow at speedsupto 30mph(48 km/h). is inplace. The roof canbeactuated including openeven whentheroof can bepower-adjusted to any position, glass windblocker behindthedriver Corvette Stingray convertible. The new engineering managerfor the2020 about 16sec,saidJoshHolder, program folding section to raise orlower in Holder told Automotive Engineering A one-button actuation causesthe

uses aflat-plane crankshaft. GM-developed 5.5-LDOHCV8that Michigan. Itispowered by anew Miller EngineeringofNew Hudson, by longtimeGMrace partnerPratt & the iconic 24 Hours ofLe Mans. Daytona, inJanuary2020 andincluding series, beginningwiththeRolex 24 in will compete intheGTLM endurance unveil the2020 C8.R race carwhich Racer ready the engine] isairflow,” Holdertold AE. [to thestored roof pieces ridingatop the standard Stingray. “The solution compartment inadifferent fashion than that directs airflow through theengine revised engine-compartment cooling atop theengine, theconvertible uses And withthefolded hardtop sitting protect itfrom excessive engineheat. compartment for thefolded top to panels andheat shieldsthat form the is theincorporation ofcomposite change for the Stingray convertible said perhapsthemost meaningful for theseventh-generation Corvette. which engineered theconvertible top and convertible specialist Webasto, motors andwas developed by sunroof folding hardtop system usessixelectric to generate thesame performance. The chassis are adjusted for theconvertible tuning for thestandard 2020 Corvette’s rates andmagnetorheologic-damper

The C8.Rwas designedandbuilt Chevrolet alsousedtheoccasion to Apart from visualdifferences, Holder SEPTEMBER 2020 19 Corvette Stingray folding hardtop and associated approximately hardware add convertible’s by BillVisnic The 2020 77 lb. Inside Tremec’s SUPERCAR DCT

To polish the 2020 mid-engine Corvette’s driving prowess, GM and Tremec engineers joined Tremec’s new TR-9080 forces to create family of DCTs aimed at RWD applications can handle input a new and better torque up to 590 lb-ft. Higher automated performance and efficiency versions are in development. transaxle. By Don Sherman

xplaining Corvette’s move to one transmission for all components and attributes. Celebrating the DCT’s buyers, global chief engineer Tadge Juechter notes, “Our claim to fame, Corvette chief engineer Ed Piatek customers began requesting a dual-clutch automatic notes, “They change gears quicker than any human transmission [DCT] several years ago. Following the can shift a manual transmission.” His team was Eintroduction of the C7 Corvette in 2014, our take-rate for sticks convinced that a DCT was the optimum solution [manual gearboxes] fell from 50 percent to less than 20 percent for the all-new Corvette and steered Tremec in that this year.” Searching the globe – read Europe – for a suitable direction from the onset of C8 development. DCT, Juechter’s team found none with sufficient torque capacity Like conventional automatics, DCTs upshift to survive behind the lively LT2 6.2-L V8 planned for the all- without interrupting the flow of torque to the new 2020 mid-engine edition of GM’s reimagined sports car. drive wheels. Like manual transmissions, they To solve that dilemma, discussions began with Tremec, the employ clutches and helical gears versus a torque Mexico City-based manufacturer which has supplied GM, Ford converter whirling planetary gears. Porsche and FCA with manual transmissions for two decades. While especially has enjoyed great success with what it Tremec had the expertise to make the mechanical components calls PDK (Porsche DoppelKupplungsgetriebe), packed inside a dual-clutch box, the automated half of the the most popular transmission type across its equation – mechatronic actuators to engage the clutches and lineup. Understandably, GM and Tremec engineers shift the gears – was beyond their ken. Tremec filled that need used PDK as their key performance target. in 2012 by purchasing Hoerbiger Drivetrain Mechatronics, a Belgium-based supplier of electronic dual-clutch actuators with Packaging triumph a customer list including AMG-Mercedes, Ferrari and McLaren. Tremec owner Grupo Kuo announced its Invented by Citroen in the 1930s and patented by Imre Szodfridt investment in DCT technology in 2016. The new

in 1969, DCTs consist of a mix of manual and automatic transmission TR-9080 family is aimed at high performance TREMEC GM IMAGES: BOTH

20 SEPTEMBER 2020 ENGINEERING THE C8 CORVETTE SPECIAL REPORT Mechatronics know- how helped Tremec engineers design a super-compact unit. TR-9080 is available with both mechanical and electronic limited-slip diffs.

rear-drive applications. The first mLSD and eLSD (mechanical and electronic limited-slip) versions are capable of handling 590 lb-ft (800 Nm) input torque at up to 7,500 rpm. Higher performance and efficiency versions are in development. A look inside the Corvette’s TR 9080 reveals the densest package of shafts, gears, actuators In the DCT, torque and electro-hydraulic servos to be found in any exits the counter shaft modern automobile. Five aluminum castings support via helical gears that the two clutches, six shafts, five synchronizers, spin the adjoining two dozen gears, five shift rods and multitude pinion shaft which is of bearings needed to provide eight forward in mesh with a spiral- speeds, reverse, and lockup for parking. bevel ring gear. Add to that three electrohydraulic control bodies, an assortment of speed and position sensors, and a master electronic controller managing every aspect of the TR 9080’s operation. The 8.8:1 overall ratio spread yields nose-bleed launch acceleration, quiet and efficient cruising, and a gear for every in-between occasion. The mLSD variant is standard in the base Corvette and the eLSD optional (with the Z51 Performance Driving package). Connecting the LT2 engine’s crankshaft to the TR 9080’s clutch basket is the responsibility of a flywheel carrying the starter ring gear and a centrifugal pendulum damper that’s needed to quell torsional vibrations erupting during the engine’s migration between V4 and V8 firing modes (a fuel efficiency improver). Tremec purchases this assembly from a Tier-2 supplier. the other main shaft which carries even-numbered ratios located Next in line are the two normally open wet forward in the transaxle. These two main shafts are concentric, clutches positioned concentrically to save space. with the inner clutch connected to the outer shaft and vice versa. Hydraulic pistons rotating with the clutches force As in manual transmissions, all main shaft gears are permanently them into engagement when commanded to do so meshed with mating gears spinning on the counter shaft. No torque by the transaxle’s electronic control module. The is delivered until two of the five triple-cone synchronizers are outer clutch’s five driven plates spin the main shaft moved by a computer-controlled actuator to connect the selected carrying odd-numbered gears located at the rear gears to the main (input) and counter (output) shafts. Torque of the transaxle. The inner clutch’s six driven plates exits the counter shaft via helical gears that spin the adjoining

TREMEC GM IMAGES: BOTH (more because they’re smaller in diameter) spin pinion shaft which is in mesh with a spiral-bevel ring gear.

ENGINEERING THE C8 CORVETTE SPECIAL REPORT SEPTEMBER 2020 21 Inside Tremec’s recommended filter replacement every 7,500 miles(12,070 km). The fluidchangeinterval km)witha is22,500miles (36,210 (circulating enginecoolant) mounted atop thetransaxle. driven pump, andcooled by astacked-plate heat exchanger supply iscarriedinabottom pan,pressurized by agear- 4 synthetic fluidsuppliedby Fuchs Lubricants. An11-liter servo actuator needs.The magicelixirisaPentosin FFL- 9080’s lubrication, cooling, clutch conditioning, andhydraulic faced was developing asinglefluidto serve alloftheTR sourced components. Oneofthemajorchallengesengineers ft2 Wixom, Michigan,facility openedin2017, usingglobal- mode ‘Burn-out’ in thedownshift—as in7thto 4th,6thto 3rd, or5thto 2nd. will skipratios, aslongbotheven andoddgears participate command maximum forward thrust. Inthisinstance, theTR9080 or stop. The exception iswhenthedriver floors thethrottle to is skippedwhenthecaraccelerates from rest orslows for aturn torque hasto gosomewhere (unless neutral isselected), nogear and thesolenoidsare engineered for fast action. Becausethe expeditious response, hydraulic circuits are asshortpossible during whichthere isnointerruption intorque delivery. To assure gear inuseisfullyreleased. That process lasts 100milliseconds, ratio. Transmission gearratios (see table) are common. receive anelectronically modulated limited-slip diffwitha5.17:1 4.89:1 final-drive ratio. Customers optingfor theZ51 option equipped withamulti-plate limited-slip differential witha below thefinaldrive andcounter Corvettes shafts.Base are has theinputshaftslocated at thebottom ofthetransaxle, mm) lower thantheC7edition,TR9080’s architecture 22 SEPTEMBER 2020 Tremec assembles theTR9080at a$50-million, 125,000 During anupshift,thenext ratio beginsengagingbefore the To facilitate mounting theCorvette’s engineoneinch(25 SUPERCAR DCT

buyers inlinefor delivery beginningMarch 2020. satisfy –theoneswhomatter most –are Corvette DCT isMission Accomplished. The tougher criticsto reviews have already declared that theTR9080 behavior provided by past automatics. Earlypress engineers hadto venture far beyond theplacid shift transmission from theoptionssheet, Corvette will switch thetransmission to Manualshift mode. releases bothclutches. InDrive, pullingonepaddle engages. Pullingbothshiftpaddlessimultaneously is heldat 3,500rpmbefore thefirst-gear clutch during therace through thelower gears. The engine tires, andlaunchcontrol to optimize enginerpm 9080 provides modeto a‘burn-out’ warm therear 60-mph performance claimedby Chevrolet, theTR shifts. To achieve 2.9-3.0-second thecar’s 0-to- hold agearduringthrottle liftto avoid unnecessary during hard lateral acceleration exiting abend,and aggressive braking before acorner, delay anupshift instrument display functions to theirliking. customize engine, transmission, suspensionand conditions. Two additionalmodesallow drivers to Weather calibrations tailored to prevailing road the center console selects Tour, Sport,Track and the driver instant authority. ADriver Modeknobon attached to theCorvette’s steering wheelprovide respond withimpressive performance. Shiftpaddles programmed to interpret thedriver’s intentions and interruption duringshifts,thenew TR9080is with eight gearratios andthelackofthrust To compensate for eliminating atraditional stick- This smarttransmission willdownshift earlyduring Aside from theremarkable acceleration available ENGINEERING THEC8CORVETTE SPECIAL REPORT to 2nd. 4th, 6thto 3rd, or5th downshift, i.e., 7thto participate inthe even andoddgears ratios, aslongboth The TR9080willskip installation (at right). ratio chartandDCT C8 Corvette gear

LINDSAY BROOKE

GM LINDSAY BROOKE

GM the details Sweating DEVELOPMENT S SPECIAL REPORT ENGINEERING THEC8CORVETTE SPECIAL placed onthefirewall wasn’t aseffective inmuffling only afoot from theoccupants’ ears. Insulation caused concern, asthenoisewas being generated water pumplocated at thefront oftheengine. This accessory drives for thealternator, AC compressor and a high-frequency whirringnoiseemanating from 458 for testing andtear-down analysis. Engineering. HesaidGMalsopurchased a Ferrari Juechter, inaninterview withSAE’s Automotive revealed executive chiefengineerTadge automatic transmission’s overall dynamics,” especially inreference to theirPDKdual-clutch encountered reinventing America’s sportscar. hoopla: how GMengineers solved problems they mission accomplished, there are lessons behindthe drive reviews and‘Of theYear’ trophies mark that increased rear-tire loading.While numerous test- acceleration, braking andhandlingviasubstantially eighth-generation (C8) Corvette was to improve motive behindadoptingamid-enginelayout for the Stingray into abuddingsupercar. General Motors’ a mid-enginearchitecture. tackled challengesinthemove to How GM’s Corvette engineers The first runningStingray prototypes exhibited “Porsche was ourprimarybenchmark, feet transformed the2020 Chevrolet Corvette of transmission components aftby almost three by 7.5 feet m)andmoving (2.3 300lb(136kg) hifting 500lb(227 kg) ofenginemass rearward OF C8 by DonSherman

and whenthecar isparked following adrive. Afan helpsvent passes large volumes ofhot,wet vapor duringrainy driving moisture from theenginebay. What Juechter callsC8’s “chimney” the glass hatch andsurrounding surfaces must vent heat and In additionto providing rear visibility, thebottom edgeof the long,nearlyhorizontal hatch over theenginecompartment. both thenear-vertical glass panelintherear cabinbulkheadand audible fuel-injector noise intheproduction cars. Further dialing-in ofbuildprocesses isaimedat eliminating cockpit issufficiently robust to hushthebeltwhir,” Lee said. the sealaround thelaminated acoustic glass at therear ofthe developing effective insulation materials andassuring that using anisolated arrangement inthesmallblocksince 2014. between theengine’s cylinder headsandfuelrails, GMhasbeen that while most competitors hard-mount theirfuelinjectors such asbeltwhir, injector tickandvalvetrain clicks.” Henoted engine’s throaty intake andexhaust rumble, over distractions “It’s abalancingact —hearing thesatisfying sounds,suchasthe glass shrouding theenginebay,” heexplained. three timesasthickthe3.2-mm (0.13-in) tempered of acoustic glass to 8.6 mm(0.34 in),whichisnearly analyzed Ferrari’s solution:anunusuallythickrear window. the noiseasengineers hadhoped,Juechter noted. So, they aluminum-intensive spaceframe laidbare. Corvette’s new A related issue isthat thedriver’s view rearward isthrough “For C8,GM’s NVHengineers invested extra effort in Jordan Lee, globalchiefengineerfor GM’s small-blockV8,added: “For C8,we increased the thickness ofthat piece SEPTEMBER 2020 23 the details Sweating DEVELOPMENT reservoir that’s now standard equipment, we encountered virtually uncompromised. “Thanks to thenew engine-mounted dry-sump oil scavenge pumpsto assure that track performance would be was oilblown outtheoptional drysump’s vent system. the tankwas starved duringhigh-gmaneuvers.” Anotherissue a needle. We lost several C7engineswhentheoilpickup in generation Corvette, “dialing inthe lubesystem was like threading lubrication system. Lee explained that withtheprevious- engineers knew itwas essential to improve the6.2-L LT2 V8’s Stymied by theFEAD have aconventional backup camera asstandard equipment. eyes to focus whenthecamera view isinuse. AllCorvettes reviewers have reported that ittakes asecond orsofor their unobstructed by thewideroof pillars and often-soiled hatch glass. Assuming the lensisclean,camera provides abroad rear view, high-definition camera mounted to thetrailing edgeoftheroof. panels. The second choice isanelectronic display provided by a mirror. Modeoneoffers aconventional view through thetwo glass 2LT and3LT interior trimare equippedwithatwo-way center is diminished.To address thisconcern, Corvettes withup-level connectors subjected to road splashhave weathertight seals. that heat from theenginebay. Inaddition,alltheelectrical slight amount ofundersteer duringnormalstreet driving. near-neutral characteristics onthetrack witha The C8chassis isdesignedto deliver Built for speedand for comfort: 24 To solve theseproblems, theC8program opted for two additional Given theC8’s aggressive cornering capability, powertrain As isnotuncommon inotherrearview camera-mirror applications, When thehatch glass issoiled,thedriver’s view to therear SEPTEMBER 2020 OF C8

versus-deflection characteristics. “To match theride difference between composite- andcoil-spring force- Juechter saidthiswas becauseofthesignificant springs, theengineers hadto follow suit infront. exact samespace asspinningtransmission gears.” of thechassis, thearc ofthespringwould occupy the that arear composite springrequires. Inarear view transaxle, there’s noroom for thetallcrosscar path “Unfortunately, withourlow-mounted engineand efficient from amass standpoint,” Juechter explained. keep thecomposite springsbecausethey are quite in 1981)to steel coils. “We would have preferred to suspension springs(pioneered onCorvette’ rear axle engineers alsoswitched from semi-ellipticcomposite necessary onlyevery 100,000 milesorso. can onlyhopethat willbearare occurrence transaxle assembly from thecar. Corvette owners Doing sorequires dropping theentire engine- front-of-engine accessory drive (FEAD) belts. is astraightforward procedure for replacing the program we experienced onlyoneenginefailure.” works andthroughout C8’s comprehensive test Lee reported. “We were astounded how well it no [oil-starvation] drama duringdevelopment,” Once C8’s rear suspensiondesignchanged to coil While shuffling powertrain component locations, C8 One challengethat hasthusfar stymied engineers ENGINEERING THEC8CORVETTE SPECIAL REPORT

GM

BOTH IMAGES: LINDSAY BROOKE GM

BOTH IMAGES: LINDSAY BROOKE SPECIAL REPORT ENGINEERING THEC8CORVETTE SPECIAL it flows rearward, raising theheight ofthecatalytic gone andC8’s exhaust system sweeps upward as substantial pockets cast into ournew spaceframe.” the tires andare anchored at theirupperendsby previous composites, they reside above thetops of rear coil springsare notonlyheavier thanthe parts that are higherthanbefore,” hesaid.“The as low aspossible inthechassis, there are several “While C8’s engineandtransaxle are bothmounted Confirming that, Juechter shedlight onthesituation: increase intheCorvette’s center-of-gravity height. configuration, according to GMengineers. roof panelinplace and12%stiffer intheopen torsional stiffness is7%greater thanC7withits knuckles are stiff aluminumforgings andcastings. components. AsinC7, suspension control armsand attaching holeandform threads to secure frame drill screws usedat dozens oflocations pierce an variety offasteners andstructural adhesive. Flow- stampings andhydroformed partsjoinedwitha facility —plus14conventional castings, extrusions, they’re manufactured at GM’s Bedford, Indiana, engineering team dubbed“the Bedford Six”because elaborately ribbeddiecastings —whichthe a new aluminumspaceframe consisting ofsix Rear-tire mass loading steel coil springat eachcorner,” heexplained. we deemabsolutely essential —we switched to a and roll rates at bothendsofthecar—something springs usedonprevious Corvettes. would have preferred to retain thesemi-ellipticcomposite Executive chiefengineerTadge Juechter saidhisteam In addition,C7’s low-mounted torque tubeis In itsC8review, Car and Driver reported an Thanks to themore robust spaceframe, C8’s The otherfundamental C8designchangeis personally prefer the lookofslotted rotors, they’re goneinC8.” water from thefriction surfaces during wet driving.While I no longerusethedrilledandslotted rotor venting that flushes permissible. To avoid abrasion ofthenew padmaterial, we can our previous pads’25-percent copper content isnolonger 20% oftotal PM2.5 (fineparticulate) vehicular pollution. vehicle brake-pad abrasion isthesource ofapproximately emissions. Studies have shown that thedust created by tightening EPA andglobalregulations for brake-dust its rear tires isagreater influence onoverall performance.” traction achieved with60percent ofthe Corvette’s mass loading yield alow polarmoment ofinertia.Intheend,added So, positioningtheengine nearthemiddledoesn’tautomatically at theopposite endofthe car, well behindthecenter ofmass. of thecar,” MacDonaldnoted. “And ourfairly heavy transaxle lives components now reside somedistance from thecenter ofgravity. figures ofbothC7andC8“pretty comparable.” That said,two substantial performance managerAlex MacDonaldcallsthepolar-moment-of-inertia optimum agility. Asked to compare C8anditspredecessor, vehicle powertrain layouts isto minimize polarmoment ofinertiafor thecar’s height is470 mm(18.5in)—15(0.59 in)higherthanC7’s. converters, Juechter noted. The net result: theC8’s center-of-gravity section center-tunnel structure. Details ofC8’s magnesiumcrosscar beamandinstrument module. Note deep- by only70 lb (32 kg) over itspredecessor despite added handlingand ridequalityBalancing “We hadto reinvent ourbrakes,” Juechter explained, “because Another non-trivialchallengefacing theC8team was “C8 hastwo large radiators fullofcoolant situated inthenose An oft-sighted reason for choosingmid-engineover alternative An unsungC8achievement isabasecurbweight increased SEPTEMBER 2020 25 Sweating the details OF C8 DEVELOPMENT

C8 rear structure is a feast of clever engineering solutions. Note near- vertical rear window aperture, side-mounted engine bay fan, exquisitely webbed castings, and carbon-composite rear bumper beam.

The C8 team had to rethink Corvette’s foundation brakesets to features: roomier passenger accommodations, the new Tremec meet stricter global regulations for brake dust emissions. TR-9080 8-speed dual-clutch automated-manual transmission with one more gear than C7’s manual transmission, dry-sump lubrication, increased cooling capacity and larger rear wheels and “In the past, we pushed our front-engine tires. Even with the more stringent 2020 EPA test procedures, performance limits with near-racing tire compounds highway fuel efficiency increases by 2 mpg (to 27 mpg). and steering geometry favoring handling,” he To hold the line on weight, Juechter’s team supplemented said. “Unfortunately, below 40-degrees F, this its sharp-pencil engineering with a few carbon-fiber composite results in stick-slip tire chatter that owners notice. components. One is an industry-first curved and hollow rear bumper To improve this in C8, we revised the steering beam. The supplier, Shape Corp., uses pultrusion technology geometry to improve the Ackermann correction developed by Germany’s Thomas Technik and Innovation to draw and walked back a bit from our previous aggressive carbon fiber material, wet with urethane-acrylate resin, through tire compounds because they’re less essential with a die. The resulting beam, which is 4.9-lb (2.2-kg) lighter than an mid-engine to achieve our performance goals.” aluminum extrusion, bolts to the Corvette’s spaceframe extensions. The net result, Juechter noted, “is nowhere near Another ultralight part is the center tunnel close-out panel, as much stick-slip chatter as we had in C7, even with supplied by the Molded Fiber Glass company. It is made using the tighter turn circle provided in C8’s equipped MFG’s PRiME liquid composite molding process. Two carbon with our MR (magnetorheological) dampers.” fiber and three fiberglass sheets wet with vinyl ester resin are Now in their fourth design generation, the highly molded under pressure, yielding a stiff 10.4- x 49.5- x 0.16-in effective MR dampers supplied by BWI cost $1,895 (26.5 x 125.7 x 4.0-mm) panel weighing only 4.9 lb. It attaches over the $5,000 Z51 Performance Package. to the bottom of the aluminum spaceframe with 30 fasteners. The Corvette development team collaborated The new Corvette’s passenger compartment floor panels are five years with Michelin to develop new run-flat SMC (sheet molding compound) moldings topped with stamped tires for C8. The base rubber is a Pilot Sport ALS aluminum panels at the rear to support the car’s bucket seats. (all season) while Pilot Sport 4S (summer only) Front and rear luggage-compartment bins made by MFG use radials are included with the Z51 option. This is the ultralight SMC with a specific gravity below 1.0 — indicating first application of all-season tires on the Corvette, that each part would float in water. A die-cast magnesium which should encourage owners to use this supercar crosscar beam bolts between the A-pillars to rigidly support more months of the year in northern climes. the dash panel. For the first time, the Corvette’s bottom Juechter is on record not wanting C8 to be a surface is flat and smooth to minimize aerodynamic drag. handful at the cornering limit — a preference dating One enduring C7 owner gripe is front-tire chatter during cold- to his youth under the wing of a fighter-pilot father weather, full-steering-lock maneuvering. According to Juechter, who enjoyed owning and driving Porsche 911s.

considerable effort was invested in remedying that shortcoming. “We definitely didn’t want our first mid-engine BROOKE GM; LINDSAY FROM LEFT: RACING RICHARD PRINCE/CHEVY

26 SEPTEMBER 2020 ENGINEERING THE C8 CORVETTE SPECIAL REPORT Developed in parallel with the 2020 Corvette Stingray, the C8.R racecar driven by Antonio Garcia, Jordan Taylor and Nicky Catsburg earned a fourth-place finish in its maiden race at the Rolex 24 At Daytona to start the IMSA WeatherTech SportsCar Championship. The trio completed 785 laps for 2,794.6 miles — the greatest distance for any Corvette entry in Rolex 24 history.

effort to earn a reputation as a car that’s tricky nose tip and front corners drawn back tight — seemingly a at the limit,” he asserted. “There are numerous triumph of styling over engineering. The car also is 2.2 in (5.6 variables that must be addressed to achieve benign, cm) wider and 5.3 in (13.5 cm) longer than its C7 predecessor. totally controllable handling. By that, I mean The increase in length is attributable to ergonomic and storage near-neutral characteristics on the track with a improvements. Fore-aft seat travel was increased by an inch bit of understeer during normal street driving.” (25.4 mm) and the seat-backrest recline angle doubled, to 18 A key variable is lateral compliance, which begins degrees, to better accommodate tall occupants. The C8’s extra at the tire sidewall and continues through the length also provides storage space in the rear trunk for the wheel’s construction, wheel bearings, suspension removable roof, a feature considered essential in Corvettes. knuckles, rubber bushings and control arms all The increase in overall width is due to wider rear tires and the way to the suspension anchor points on wheels. “It’s not practical to tuck them in closer to the centerline the spaceframe. “We want the tire’s stick-slip if you want outstanding ride and handling balance,” Juechter characteristics to be very progressive with gradual said. “We prefer long suspension travel with lower spring rates changes in the coefficient of friction,” Juechter than are common in competitors. Shortening the halfshafts isn’t explained. Suspension geometry was tailored to practical because that increases universal-joint angularity, greatly provide a small amount of steering into the turn as reducing the life of the rubber boots surrounding the U-joints.” the car rolls. The lateral compliance built into the Also contributing to the C8’s added width is the substantial duct suspension bushings also provides a few minutes integrated into each rear quarter panel. These openings are responsible of steer angle under high lateral loading, he said. for ingesting an enormous volume of air for engine induction and Engine-mounting strategies were also deliberated, engine-bay cooling (cars equipped with the Z51 performance package with the team deciding to “softly” mount the LT-2 have a third radiator on the passenger side to assure that they’re V8 for vibration isolation. “But you definitely don’t fully track capable at ambient temperatures of 100 degrees F). want a two-stage step function when the engine Juechter acknowledges that the wider fenders and rear tires are reaches the limit of its roll,” Juechter explained. “So, responsible for a frontal area that’s slightly greater in C8 (2.075 the compliance and damping built into the engine m2/22.3 ft2) than in C7 (2.023 m2/21.78 ft2). Because aerodynamic mounts are also important.” Finally, spring, anti-roll downforce is notably greater with the Z51 performance package, a bar and damper calibrations were selected to work C8 so configured has an 0.322 drag coefficient versus C7’s 0.313 Cd. with all the other variables to give the driver the The bottom line is a 2020 Corvette Stingray chassis and perception of a totally integrated driving experience. body engineered to fully exploit the performance strides delivered by the SAE-certified 495-hp LT2 V8 and the Tremec Dimensional factors DCT. Considering the new Corvette’s $59,995 base price In the plan view, the 2020 Corvette Stingray and the sold-out 2020 production run, Juechter’s team has

FROM LEFT: GM; LINDSAY BROOKE GM; LINDSAY FROM LEFT: RACING RICHARD PRINCE/CHEVY has a fighter-jet look with an aggressively curved seemingly wrought the supercar value of the century.

ENGINEERING THE C8 CORVETTE SPECIAL REPORT SEPTEMBER 2020 27