Tweet
Here's a nice article on the engineering and design of the C8 from the SAE website; written by Don Sherman.
https://www.sae.org/news/2019/07/202...corvette-intro
Originally posted by SAE
Engineering the 2020 Chevrolet Corvette
2019-07-22 DON SHERMAN
The eighth-gen (C8) Corvette is a creative mix of novel and traditional engineering solutions unleashed at a shockingly low base price.Two days before the 50th anniversary of astronaut Neil Armstrong’s leap for mankind and 10 years after General Motors emerged from bankruptcy, the camouflage was finally ripped from the eighth-generation (C8) 2020 Chevrolet Corvette. As widely anticipated, C8 now flaunts a mid-engine layout that ostensibly puts it on equal terms with the world’s most venerated supercars.
After six decades of experimentation and concept-car teasing, GM acknowledged that the new Stingray will enter production before year’s end. The truly shocking announcement is a base price less than $60,000, barely $4,000 more than today’s front-engine C7. Along with moving the cockpit forward 16.5 inches (419 mm) to facilitate shifting the engine rearward, the new Corvette is an innovative mix of novel and traditional engineering solutions.
New V8 and DCT powertrain
GM’s new LT2 fifth-generation small-block V8 may have roots extending back to 1955, but it brings a long list of new features to the party. Its aluminum block has revised oiling and venting arrangements in support of a dry-sump lubrication system with one pressure and three scavenge pumps. The sump casting is shallower to allow mounting the engine 1 in. (25 mm) lower in the car versus C7. The crankshaft nose is longer, to power revised accessory drives. There’s an oil reservoir mounted at the top-left corner of the engine and the oil cooler’s capacity is 25% greater than in C7 for more dependable operation during extreme (track or desert driving) conditions.
More aggressive valve timing and 11.5:1 compression along with new intake and exhaust manifolds raise output to an SAE-rated 490-495 hp (365-369-kW) at 6450 rpm (with and without the optional low-restriction exhaust system). Peak torque is rated at 465-470 lb-ft (630-637 Nm) at 5150 rpm. The LT2 is redlined at 6500 rpm. Cylinder deactivation remains to help enhance fuel economy.
Asked what kept GM from clearing the worthy 500-horsepower (373-kW) hurdle for the 6.2-L LT2, Jordan Lee, the global chief engineer for small-block engines, acknowledged, “Honesty stopped us at the level we were confident could be provided in all of the engines we’ll build for the new Corvette. As the only naturally-aspirated V8 in the segment, this engine will deliver the visceral experience expected of a Corvette,” he told Automotive Engineering during the car’s unveiling in Tustin, California.
Tremec will supply a U.S.-made 8-speed dual-clutch automated-manual transmission with paddle shift control. Along with the absence of a clutch pedal, a conventional shift lever is also a thing of the Corvette’s past. Instead, two console-mounted pull toggles select Drive or Reverse while three buttons choose either Park, Neutral, or the Low/Manual modes. Executive chief engineer Tadge Juechter added, “Regardless of driving mode, our performance shift algorithms are so driver-focused they can sense spirited driving and hold lower gears longer for optimum throttle response.”
Explaining the loss of the manual transmission selected by 20% of C7 buyers, Juechter noted, “With no interruption of torque delivery during upshifts, the DCT is the superior performance solution. Squeezing a clutch pedal into the foot box and shift linkage down the structural center tunnel would have posed design compromises we weren’t prepared to make. And we know our customers will be thrilled with the sub-3-second zero-to-60 [mph] acceleration we’ve achieved with the Z51 [equipment] option.”
To exploit the benefits of a mid-engine car’s enhanced traction at the rear wheels, first gear provides more torque multiplication, while seventh and eighth are tall overdrive ratios for quiet and efficient highway cruising. The middle five gear ratios are closely spaced for optimum acceleration and track performance. Like a race car, the transaxle’s input shaft is positioned below (versus above) halfshaft height to facilitate mounting the engine lower in the car. Electronic traction management and limited-slip differential controls are both available.
In addition to previous Weather, Tour, Sport and Track driving modes, two additional choices have been added to C8. MyMode is a configurable setting, and “Z mode” goes beyond MyMode to permit tuning of up to twelve engine, transmission, steering and damper performance variables.
Thermal-management challenge
Asked to name the greatest challenge faced during C8 development, Juechter doesn’t hesitate to cite the cooling system. “With the engine and radiator up front, cooling air entering the nose sweeps through the heat exchangers, over the hot exhaust manifolds, out the fender wells and side gills, or under the car. That’s straightforward,” he explained. “The solution for the mid-engine Stingray we validated at 100-degrees F with a pro driver at the wheel is significantly more involved. There are two radiators in front and a third positioned in the left-side scoop, which also routes fresh intake air to the engine.
“Airflow has to bend abruptly toward the car’s centerline before sweeping past the exhaust headers. Then it slams into our huge rear trunk wall. Since there’s no room for ductwork, we fitted large air outlet vents, aided by electric fans, in the rear corners of the car to cool the powertrain during sweltering traffic conditions,” he said. In addition, the cantilevered glass hatch has an open “mail slot” at its trailing edge to vent hot air. “The DCT’s substantial cooling needs are satisfied using a lubricant-to-coolant heat exchanger mounted atop the transaxle and a dedicated flow loop,” Juechter added.
Structure from experience
Like the C7, the new C8’s structure is a welded-aluminum spaceframe built at GM’s Bowling Green, Kentucky, assembly plant. This second-generation design consists of stampings, extrusions, castings, hydroformed tubes and six intricate die-cast aluminum assemblies aimed at improving torsional rigidity while also reducing the number of welds. Known as the ‘Bedford Six,’ these structural nodes are made at a GM Powertrain plant in Bedford, Indiana.
Thanks to its robust 12-in. (305-mm)-tall center tunnel, the new spaceframe is relatively light and claimed to be 10% stiffer than before to provide a solid foundation for steering, suspension and powertrain components. With no need for tall, wide rocker sections to supply the desired structural integrity, the C8’s ingress and egress are exemplary.
Suspension control arms are cast- and forged-aluminum as before. In place of the fiberglass monoleaf springs long employed in Corvettes, C8 has conventional coil springs encircling a damper at each wheel location. GM’s optional Magnetic Ride Control, which senses wheel motion and automatically adjusts the dampers using BWI’s magneto-rheologic technology, has been retuned for improved ride and handling.
“No Corvette has ever felt so comfortable, nimble, and stable,” Juechter exclaimed. “We’re confident our customers will admire the strides we’ve achieved in ride quality. And now that the car’s center of gravity is very close to the occupants’ hip points, the feeling during acceleration and braking is analogous to riding at the center—instead of the ends—of a teeter-totter. There’s practically no sense of pitch motion in the cockpit.”
Moving the engine rearward also cleared a path for a straighter, stiffer connection between the steering wheel and the electrically-assisted rack-and-pinion gear. Less weight on the front wheels enabled quickening the steering ratio from 16.25:1 to 15.7:1 to sharpen agility. Michelin will continue as Corvette’s sole tire supplier. Standard tires are Pilot Sport ALS (all season) radials while Pilot Sport 4S (summer) rubber is included with the optional Z51 performance package.
The 20-in. (508-mm) diameter rear wheels are an inch wider than before, while rear tire section width has been increased by 20 mm (0.8-in.) in keeping with the increased rear-axle loading. Brembo will continue supplying the four-piston fixed caliper, vented-rotor brake components but no longer delivers corner modules to the Bowling Green manufacturing plant. The brake booster is electrically powered.
New mid-engine packaging
Here the C8 bears little resemblance to its immediate predecessor. Except for a 2-in. (51-mm) loss of hip room, occupant space is unchanged. Rearward seat travel is an inch longer and the backrest recline angle is nearly doubled to better accommodate taller occupants. In spite of a more steeply angled hood and low cowl height, there’s space available in the front cargo compartment for a carry-on suitcase and a briefcase.
The rear trunk will swallow two sets of golf bags or the standard removable roof panel. An entertaining view of the well-dressed LT2 V8 is available through the hatch glass, which has an unsealed trailing edge to vent heat. Key dimensions are larger: 0.5-in. (12.7-mm) of increased wheelbase; 5.4-in. (137-mm) longer overall length; 2.2-in. (55.9-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 panels are sourced from Plasan Carbon Composites. The exterior fascias, in TPO, are from Magna, as is the Stingray’s removable roof panel. The rear bumper 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. (181 kg) of downforce at speed. Relocating the exhaust outlets to the rear corners of the car clears a path at the center for a more-efficient air diffuser.
Inside, attention to detail is evident in the standard leather seat and dash trim adorned with contrasting color stitching. Instead of molded plastic door and console surfaces, aluminum or genuine carbon-fiber panels are fitted. Speaker grilles are stainless steel. Vertically-oriented vents and climate controls help reduce the height of the instrument panel, enhancing the feeling of spaciousness.
C8’s small-diameter, two-spoke steering wheel is flattened top and bottom to avoid obscuring the view of the 12-in. (305-mm) reconfigurable instrument cluster. There are three seat choices to balance comfort and support under aggressive (racetrack) driving conditions, six interior colors, two optional upholstery stitch choices and six seatbelt colors. Add to that two wheel designs and an 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
A new 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 verges, an optional lift system increases front ground clearance by 40 mm (1.6 in.) in 2.8 s. That equipment can be programmed using GPS data to remember thousands of raise-the-chin locations.
Considering the revolutionary design, engineering and development invested in C8, it’s evident why this latest Corvette was a long time coming. Now that this Ferrari-for-working-stiffs is here, the anticipation will begin concerning more powerful editions, a potential Cadillac-branded version of the Stingray and how electrification might stretch Corvette’s appeal into unexplored territory. C8 is off to an auspicious start.
2019-07-22 DON SHERMAN
The eighth-gen (C8) Corvette is a creative mix of novel and traditional engineering solutions unleashed at a shockingly low base price.Two days before the 50th anniversary of astronaut Neil Armstrong’s leap for mankind and 10 years after General Motors emerged from bankruptcy, the camouflage was finally ripped from the eighth-generation (C8) 2020 Chevrolet Corvette. As widely anticipated, C8 now flaunts a mid-engine layout that ostensibly puts it on equal terms with the world’s most venerated supercars.
After six decades of experimentation and concept-car teasing, GM acknowledged that the new Stingray will enter production before year’s end. The truly shocking announcement is a base price less than $60,000, barely $4,000 more than today’s front-engine C7. Along with moving the cockpit forward 16.5 inches (419 mm) to facilitate shifting the engine rearward, the new Corvette is an innovative mix of novel and traditional engineering solutions.
New V8 and DCT powertrain
GM’s new LT2 fifth-generation small-block V8 may have roots extending back to 1955, but it brings a long list of new features to the party. Its aluminum block has revised oiling and venting arrangements in support of a dry-sump lubrication system with one pressure and three scavenge pumps. The sump casting is shallower to allow mounting the engine 1 in. (25 mm) lower in the car versus C7. The crankshaft nose is longer, to power revised accessory drives. There’s an oil reservoir mounted at the top-left corner of the engine and the oil cooler’s capacity is 25% greater than in C7 for more dependable operation during extreme (track or desert driving) conditions.
More aggressive valve timing and 11.5:1 compression along with new intake and exhaust manifolds raise output to an SAE-rated 490-495 hp (365-369-kW) at 6450 rpm (with and without the optional low-restriction exhaust system). Peak torque is rated at 465-470 lb-ft (630-637 Nm) at 5150 rpm. The LT2 is redlined at 6500 rpm. Cylinder deactivation remains to help enhance fuel economy.
Asked what kept GM from clearing the worthy 500-horsepower (373-kW) hurdle for the 6.2-L LT2, Jordan Lee, the global chief engineer for small-block engines, acknowledged, “Honesty stopped us at the level we were confident could be provided in all of the engines we’ll build for the new Corvette. As the only naturally-aspirated V8 in the segment, this engine will deliver the visceral experience expected of a Corvette,” he told Automotive Engineering during the car’s unveiling in Tustin, California.
Tremec will supply a U.S.-made 8-speed dual-clutch automated-manual transmission with paddle shift control. Along with the absence of a clutch pedal, a conventional shift lever is also a thing of the Corvette’s past. Instead, two console-mounted pull toggles select Drive or Reverse while three buttons choose either Park, Neutral, or the Low/Manual modes. Executive chief engineer Tadge Juechter added, “Regardless of driving mode, our performance shift algorithms are so driver-focused they can sense spirited driving and hold lower gears longer for optimum throttle response.”
Explaining the loss of the manual transmission selected by 20% of C7 buyers, Juechter noted, “With no interruption of torque delivery during upshifts, the DCT is the superior performance solution. Squeezing a clutch pedal into the foot box and shift linkage down the structural center tunnel would have posed design compromises we weren’t prepared to make. And we know our customers will be thrilled with the sub-3-second zero-to-60 [mph] acceleration we’ve achieved with the Z51 [equipment] option.”
To exploit the benefits of a mid-engine car’s enhanced traction at the rear wheels, first gear provides more torque multiplication, while seventh and eighth are tall overdrive ratios for quiet and efficient highway cruising. The middle five gear ratios are closely spaced for optimum acceleration and track performance. Like a race car, the transaxle’s input shaft is positioned below (versus above) halfshaft height to facilitate mounting the engine lower in the car. Electronic traction management and limited-slip differential controls are both available.
In addition to previous Weather, Tour, Sport and Track driving modes, two additional choices have been added to C8. MyMode is a configurable setting, and “Z mode” goes beyond MyMode to permit tuning of up to twelve engine, transmission, steering and damper performance variables.
Thermal-management challenge
Asked to name the greatest challenge faced during C8 development, Juechter doesn’t hesitate to cite the cooling system. “With the engine and radiator up front, cooling air entering the nose sweeps through the heat exchangers, over the hot exhaust manifolds, out the fender wells and side gills, or under the car. That’s straightforward,” he explained. “The solution for the mid-engine Stingray we validated at 100-degrees F with a pro driver at the wheel is significantly more involved. There are two radiators in front and a third positioned in the left-side scoop, which also routes fresh intake air to the engine.
“Airflow has to bend abruptly toward the car’s centerline before sweeping past the exhaust headers. Then it slams into our huge rear trunk wall. Since there’s no room for ductwork, we fitted large air outlet vents, aided by electric fans, in the rear corners of the car to cool the powertrain during sweltering traffic conditions,” he said. In addition, the cantilevered glass hatch has an open “mail slot” at its trailing edge to vent hot air. “The DCT’s substantial cooling needs are satisfied using a lubricant-to-coolant heat exchanger mounted atop the transaxle and a dedicated flow loop,” Juechter added.
Structure from experience
Like the C7, the new C8’s structure is a welded-aluminum spaceframe built at GM’s Bowling Green, Kentucky, assembly plant. This second-generation design consists of stampings, extrusions, castings, hydroformed tubes and six intricate die-cast aluminum assemblies aimed at improving torsional rigidity while also reducing the number of welds. Known as the ‘Bedford Six,’ these structural nodes are made at a GM Powertrain plant in Bedford, Indiana.
Thanks to its robust 12-in. (305-mm)-tall center tunnel, the new spaceframe is relatively light and claimed to be 10% stiffer than before to provide a solid foundation for steering, suspension and powertrain components. With no need for tall, wide rocker sections to supply the desired structural integrity, the C8’s ingress and egress are exemplary.
Suspension control arms are cast- and forged-aluminum as before. In place of the fiberglass monoleaf springs long employed in Corvettes, C8 has conventional coil springs encircling a damper at each wheel location. GM’s optional Magnetic Ride Control, which senses wheel motion and automatically adjusts the dampers using BWI’s magneto-rheologic technology, has been retuned for improved ride and handling.
“No Corvette has ever felt so comfortable, nimble, and stable,” Juechter exclaimed. “We’re confident our customers will admire the strides we’ve achieved in ride quality. And now that the car’s center of gravity is very close to the occupants’ hip points, the feeling during acceleration and braking is analogous to riding at the center—instead of the ends—of a teeter-totter. There’s practically no sense of pitch motion in the cockpit.”
Moving the engine rearward also cleared a path for a straighter, stiffer connection between the steering wheel and the electrically-assisted rack-and-pinion gear. Less weight on the front wheels enabled quickening the steering ratio from 16.25:1 to 15.7:1 to sharpen agility. Michelin will continue as Corvette’s sole tire supplier. Standard tires are Pilot Sport ALS (all season) radials while Pilot Sport 4S (summer) rubber is included with the optional Z51 performance package.
The 20-in. (508-mm) diameter rear wheels are an inch wider than before, while rear tire section width has been increased by 20 mm (0.8-in.) in keeping with the increased rear-axle loading. Brembo will continue supplying the four-piston fixed caliper, vented-rotor brake components but no longer delivers corner modules to the Bowling Green manufacturing plant. The brake booster is electrically powered.
New mid-engine packaging
Here the C8 bears little resemblance to its immediate predecessor. Except for a 2-in. (51-mm) loss of hip room, occupant space is unchanged. Rearward seat travel is an inch longer and the backrest recline angle is nearly doubled to better accommodate taller occupants. In spite of a more steeply angled hood and low cowl height, there’s space available in the front cargo compartment for a carry-on suitcase and a briefcase.
The rear trunk will swallow two sets of golf bags or the standard removable roof panel. An entertaining view of the well-dressed LT2 V8 is available through the hatch glass, which has an unsealed trailing edge to vent heat. Key dimensions are larger: 0.5-in. (12.7-mm) of increased wheelbase; 5.4-in. (137-mm) longer overall length; 2.2-in. (55.9-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 panels are sourced from Plasan Carbon Composites. The exterior fascias, in TPO, are from Magna, as is the Stingray’s removable roof panel. The rear bumper 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. (181 kg) of downforce at speed. Relocating the exhaust outlets to the rear corners of the car clears a path at the center for a more-efficient air diffuser.
Inside, attention to detail is evident in the standard leather seat and dash trim adorned with contrasting color stitching. Instead of molded plastic door and console surfaces, aluminum or genuine carbon-fiber panels are fitted. Speaker grilles are stainless steel. Vertically-oriented vents and climate controls help reduce the height of the instrument panel, enhancing the feeling of spaciousness.
C8’s small-diameter, two-spoke steering wheel is flattened top and bottom to avoid obscuring the view of the 12-in. (305-mm) reconfigurable instrument cluster. There are three seat choices to balance comfort and support under aggressive (racetrack) driving conditions, six interior colors, two optional upholstery stitch choices and six seatbelt colors. Add to that two wheel designs and an 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
A new 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 verges, an optional lift system increases front ground clearance by 40 mm (1.6 in.) in 2.8 s. That equipment can be programmed using GPS data to remember thousands of raise-the-chin locations.
Considering the revolutionary design, engineering and development invested in C8, it’s evident why this latest Corvette was a long time coming. Now that this Ferrari-for-working-stiffs is here, the anticipation will begin concerning more powerful editions, a potential Cadillac-branded version of the Stingray and how electrification might stretch Corvette’s appeal into unexplored territory. C8 is off to an auspicious start.
Comment