In the Spring of 1957, while pondering the demise of Chevrolet’s Corvette Super Sports racer at Sebring’s 12-hour endurance race, legendary Corvette godfather Zora Arkus-Duntov concluded, “Heat source must be behind driver.” The official explanation offered for dropping out after 29 laps was a failed rear-suspension bushing, but the actual show stopper was that driver John Fitch’s feet were being cooked by the exhaust header pipes snaking around the SS’s sheet magnesium ‘firewall.’
Sixty-two years later, the Corvette development trek initiated by Arkus-Duntov’s brainstorm reached New York’s Times Square, when a camouflaged prototype driven by chief engineer Tadge Juechter (with GM CEO Mary Barra as passenger), finally confirmed that the 2020 Corvette would have its engine located behind the driver.
The 7-18-2019 date prominently displayed on both sides of the camo car is when GM will reveal details about the mid-engined Corvette, exactly fifty years after the Apollo 11 mission to the Moon. Until then we have but history and speculation—supported by interviews with five Corvette chief engineers and one retired GM vice chairman—defining the signposts and sidetracks leading to the revolutionary Corvette.
Superior vehicle dynamics
Arkus-Duntov, born in Belgium in 1909 to Russian parents, earned a mechanical engineering degree at the Charlottenburg Technical University (now the Technical University of Berlin), in 1934. In his teens, he graduated from two to four wheels as his preferred means of rapid transport. In 1941, after relocating to the U.S., he adopted the surname Arkus-Duntov out of respect for his father and step-father, both of whom shared a home with his mother and brother Yura in Leningrad, Russia.
Arkus-Duntov’s fascination with speed made him practically an eyewitness to Adolf Rosenberger’s 1924-25 racing victories with the mid-engine Benz Tropfenwagen. The next decade, the fearsome V16 mid-engine Auto Union cars conceived by Dr. Porsche’s budding design office often trumped Mercedes’ traditional front-engined Grand Prix racers. In the year of Arkus-Duntov’s epiphany (1957), F1 driver Jack Brabham’s mid-engine Cooper showed promise at the Monaco Grand Prix. Two years later, the Cooper team won the World Championship, rendering front-engined racecars obsolete.
His engineering education gave Arkus-Duntov a clear understanding of the physics underlying mid-engine car design. This is the preferred configuration for rear-driven sports cars and all race cars (rules permitting) for the following reasons: Traction while accelerating from rest and exiting turns is maximized with the engine located as closely as possible to the drive wheels.
The load transferred forward during aggressive braking helps 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-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 might enable a mid-engined, second-generation Corvette. Design studies revealed that the driver’s forward visibility and the car’s center of gravity would both benefit from moving the engine rearward. Unfortunately, problems with the transaxle resulted in its cancellation and the mid-engine C2 was stillborn.
The consolation prize was approval to build an experimental single-seater with Indy 500 potential, the first of thirteen GM mid-engine concept and show cars. Dubbed a Chevrolet Engineering Research Vehicle (CERV), this 1960 concoction had a 500-hp (373 kW) small-block V8 yielding a top speed over 200 mph (322 km/h) at the Milford Proving Grounds. Its independent rear suspension made the leap to the 1963 Sting Ray (C2) production model.
When GM politics forbade Arkus-Duntov to go racing, CERV was ‘loaned’ to a west-coast museum for display. Retrieving this stunning heirloom ended up costing GM $1.32 million at a 2017 auction.
GM Design boss Bill Mitchell joined the mid-engine game in 1962 with the Corvair Monza GT coupe, constructed with the production model’s flat-six engine relocated from behind the rear axle to the middle of the car. Driver and passenger climbed aboard by hinging the unified doors and windshield assembly up and forward in one dramatic sweep.
Responding to Ford’s ambitious GT40 international endurance racing effort, Arkus-Duntov yanked another experiment out of his sleeve. The 1963 CERV II had a centrally mounted 7.0-L big-block V8 with a transmission at each end of its crankshaft to provide four-wheel drive. Top speed climbed to 214 mph (344 km/h) in testing. Finding favor with this twin-transmission arrangement, Ferrari adopted a version of GM’s creation for its 2011 FF GT (now called the GTC4Lusso).
Alas, GM’s management chose to support Chaparral Cars in the Can Am race series instead of assaulting Ford at the 24 Hours of LeMans, so CERV II was also shelved. It too slipped from GM’s grasp, selling at a 2013 auction for $1.1 million.
After Ford finally won LeMans in 1966, GM’s Design and R&D departments teamed up to build the stunning Astro II mid-engine concept for the following year’s New York auto show. Road & Track’s cover coyly queried, “A Chaparral for Production?” Still lacking a suitable transaxle, GM answered no.
R&T again swallowed the bait two years later when another GM prototype stole the New York show, exclaiming, “We’ll stake our reputation on this being the Corvette of the future.” Called simply a Corvette Prototype (internal code XP-882), this mid-engine mirage combined a transverse small-block V8 with an Oldsmobile Toronado transaxle to drive both axles. The Ford Pantera, Mercedes-Benz C111, and AMC AMX/3 ironically all seconded the mid-engine motion at the same show. Arkus-Duntov was ready to serve this car to the Corvette faithful—but when Chevy boss John DeLorean denied that wish, he threatened to resign.
Mitchell’s next move was the 1969 Holden Hurricane concept car, constructed in Australia with a mid-mounted 253 cu. in. (4.1-L) V8 driving the rear wheels through an experimental transaxle. Mimicking the Monza GT, this two-seater’s canopy was lifted by servo motors for entry. Advanced features included one of the first back-up cameras and oil-cooled disc brakes.
The next stage of XP-882 development was a thorough redesign in collaboration with Reynolds Metals to shed weight. The new aluminum unibody trimmed 500 pounds (227 kg) for the 1972 prototype code-named XP-895, but its spot-welded-and-adhesively-bonded structure was deemed prohibitively expensive for production. Result: another dead end.
Most Corvette aficionados consider the most tantalizing mid-engine experiments to be the high visibility part of GM’s ill-fated rotary engine gambit. The XP-987 GT bowed at the 1973 Frankfurt motor show with GM-designed, Pininfarina-crafted coachwork over a Porsche 914 chassis and an experimental two-rotor engine in the middle. At the Paris salon later that year, Arkus-Duntov pulled out the stops with his awesome Four Rotor: two rotaries in series, under a stunning body fitted with folding gull-wing doors.
When GM’s rotary engine work ceased soon thereafter, a conventional V8 was transplanted under deck and the car was rechristened Aerovette. After he retired, Arkus-Duntov told anyone who’d listen that this was his all-time favorite mid-engine design.
2009: ‘The patient is dead’
When he left the building in 1975, Arkus-Duntov’s parting words to his successor were “Dave (McLellan), you must build the mid-engine Corvette.” That wouldn’t happen in the 20th century, though there was sufficient interest in the layout to create another ambitious experimental called CERV III (also Corvette Indy). This 1986 GM design study was modeled in Italy and built in England by Lotus with electronic features galore. Active suspension, four-wheel steering, drive-by-wire, and advanced navigation gear were packed into a molded-composite chassis.
The 4.3-L V8 was initially a version of the engine supplied to Indycar racers. In 1990, that power source was supplanted by a twin-turbo version of the Lotus-designed LT5 5.7-L DOHC V8. Acknowledging the benefits of moving mass rearward, McLellan did shift the transmission aft for the comprehensively redesigned 1997 fifth generation (C5) Corvette, introduced shortly after Arkus-Duntov’s passing at 86 on April 21, 1996. Like the original CERV, C5’s manual and automatic transmissions were located just ahead of the differential where they remained through today’s C7.
The most recent official ray of hope that Arkus-Duntov’s mid-engine dream was not dead was Cadillac’s Cien concept shown at the 2002 Detroit auto show. Key features were a magnificent exterior shape inspired by the F-22 Raptor fighter aircraft, scissors-hinged doors, a 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 shared the Corvette C5 and C6 platforms in its XLR luxury roadster.
Caddy version coming?
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 sports car design was wind-tunnel tested a few years ago.
McLellan’s successor Dave Hill, who coincidentally 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 C6 Z06 he created brought 505 hp (377 kW) and 7,000 rpm to the party with a 7.0-L OHV small block at the front atop an aluminum space frame. In 1993, Hill hired Tadge Juechter as his assistant whom he describes as “a wonderful engineer, team leader, and GM executive.”
Tom Wallace succeeded Hill as Corvette chief engineer in 2005. After the redoubtable 2009 Corvette ZR1 was bumped to 638 hp (476 kW) with an Eaton supercharger and intercoolers, the inevitable, ‘what’s next?’ question was asked. It was answered with ‘mid-engine’ as the most practical means of improving performance.
Juechter was the first hand-raiser, and Wallace quickly seconded the mid-engine motion, in part because of his years of amateur road racing. Chevrolet’s marketing department, also realizing this might be an excellent means of attracting younger buyers, was also enthusiastically on board. GM vice chairman Bob Lutz was skeptical at first, but he was soon convinced.
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.
On June 1, 2009, GM filed for Chapter 11 bankruptcy. Juechter, as the last Corvette engineering chief standing, continued working on a seventh-generation car for a 2014 model year introduction. Since this was hardly the opportune time to launch a flashy Corvette with a revolutionary powertrain layout, Juechter kept team heads down. They focused on launching well-received Z06, Grand Sport, and the recent 755-hp (563-kW) ZR1 editions while, behind the scenes, work intensified on the mid-engine C8 due for the 2020 model year.
Pre-July 18 speculation calls for a base LT2 6.2-L small-block V8 producing over 500 hp/373 kW (up from C7’s 455 hp). An 8-speed dual-clutch, paddle-shifted automatic supplied by Tremec and Fassler will be the sole transmission. Later in C8’s life, hotter LT-series V8s will be introduced, some with flat-plane crankshafts, others with DOHC. A top-spec twin-turbo V8 will eventually deliver over 800 hp (596 kW). “ZERV” and “ZORA” nameplates have been copyrighted by GM along with various reactive aerodynamic devices.
Three removeable targa roof designs will be offered at launch and a convertible will follow later. C8’s foundation will be a hydroformed aluminum space frame as before with composite body panels supplied by Plasan and Continental Structural Plastics. Expect a shift to coil springs (away from today’s transverse composite leaf springs) along with 245/35ZR-19 front tires and 305/30ZR-20 rear rubber by Michelin. Brembo will supply conventional and carbon-ceramic brake components as before.
The announced June 28 auction for charity of the final C7 Corvette suggests that the previously expected generational overlap will not happen. Production of C8s for publicity and engineering use is underway at GM’s Bowling Green, Kentucky, assembly plant and customer deliveries are expected to commence well before the end of 2019. Expect an attractive base price to maintain Corvette’s longstanding value proposition, with subsequent six-figure future editions capable of slaying hypercars wearing Bugatti, McLaren, Ferrari, Lamborghini, and Porsche badges.
SIDEBAR: The engineer’s engineer
He was known as Zora’s problem solver and kindred spirit, and now Gibson “Gib” Hufstader is excitedly looking forward to finally seeing Arkus-Duntov’s mid-engine dream hit the streets. Hufstader, 88, became an SAE member in 1957, the year he joined General Motors R&D following studies at the General Motors Institute (now Kettering University) and military service at the Army’s Aberdeen Proving Grounds.
During his 45-year GM career, Hufstader (left) earned seven patents for driveline-related innovations. His passion for motorsports born in 1959 persists. In the 1960s, he assisted Corvette and Camaro teams, including Roger Penske’s, in both endurance and Trans-Am events. Co-driving the Owens-Corning Corvette at the 1969 12 Hours of Sebring, he scored second in the GT class and 14th overall.
Hufstader joined the Corvette group in 1964. During that time, efforts to engineer a viable mid-engine production design persevered at what he describes as the ‘hobby’ level. “Zora would ask me to sketch layouts, initially with the Hewland transaxle, then with other arrangements to reduce length,” Gib recalls. “A transverse layout using parts of an Oldsmobile Toronado automatic transmission with all-wheel drive capability earned Zora a patent in 1971.” The patented mid-engine powertrain layout works as follows:
- Engine transversely positioned behind cockpit with west-east orientation.
- Crank-mounted torque converter drives transverse automatic transmission located ahead of engine via Morse chain.
- Bevel-gear box at transmission’s output end drives shaft passing through engine oil pan to rear axle final drive differential.
- (Optional) shaft forward from bevel gear to front axle final drive differential.
Hufstader’s most memorable project was the Four-Rotor Corvette constructed for the 1973 Paris Salon. “While that three-month effort didn’t venture beyond the show car,” he noted, “it had ample potential for further development.”
Today Gib’s hobby fleet consists of the ’67 427 Corvette he campaigns in vintage road racing, an aerobatic Steen’s Skybolt biplane, and eight motorcycles—including a 1952 Vincent Black Shadow, a 1974 Ducati 750 Super Sport and a 1956 Triumph 650 Trophy. Look up ‘engineer’s engineer’ in the dictionary and you’ll see Gib Hufstader, wearing an engaging smile. — Don ShermanContinue reading »