The Corvette C8.R is the race-going version of the Corvette C8, otherwise known as the mid-engine Corvette. The C8.R competes in the GTLM class of the IMSA WeatherTech SportsCar Championship.
October 12th 2019 closed a chapter to the end of an era when Corvette Racing crossed the finish line 4th and 9th in the GTLM class with their Chevrolet Corvette C7.R at Road Atlanta. This would prove be the last race that the Corvette Racing team would run a front engined layout as the 2020 season would be the introduction of the new mid engined eighth generation Corvette race car dubbed the C8.R.
The auto world had the date 07/18/19 marked on their calendars as General Motors would officially unveil their new eighth generation Corvette. Speculations for decades had always been around would the new Corvette finally be a mid engined layout like Zora Arkus-Duntov had dreamt of. Pre-release PR cars had Corvette chief engineer – Tadge Juechter, drive around New York City in a camouflaged wrapped C8 with the unveil date stamped across the doors. All though disguised, the car community was certain this was the new Corvette and could tell by the new shape that the engine would be mid mounted. July 18th would also be the unveil date for the new race car as unlike the previous generation Corvette the C7.R was unveiled alongside the C7 Z06 model and not alongside the Stingray unveiled the previous year. This day would not only allow the world to feast their eyes on the new look of the race car including livery but also hear the new exhaust note from the new engine.
The 2020 Chevrolet Corvette C8.R is a GTLM (Grand Touring Le Mans) race car built by Pratt & Miller for Corvette Racing that competes in the IMSA WeatherTech SportsCar Championship in the USA, and the LM GTE (Le Mans Grand Touring Endurance) class for any FIA World Endurance Championship races such as the Le Mans 24 Hours. The International Motor Sports Association (IMSA) mandates the homologation rules that are set by the Fédération Internationale de l’Automobile (FIA). These rules are designed to ensure that the race car is the closest representation to the road going equivalent, therefore many components and design cues are carried across from the road car to its racing equivalent. These homologation rules enforce that the road equivalent built by a major manufacturer must produce at least one car a week ,or for a small manufacturer one car a month . But these cars are only eligible to race after 100 road cars for big manufacturers or 25 road cars for small manufacturers are produced. The car also must have an official launch campaign and sales network.
When it comes to the powertrain, the engine must be used in a production car; while this is usually the engine from the road car, the organizing entity behind the annual Le Mans 24 Hours; ACO (Automobile Club de l’Ouest) has made exceptions for cars like the BMW Z4 GTE which used a race version V8 from the BMW M3 E92. The Corvette featured a major change from 2010 to present as engine displacement was changed to a limited size of 5.5L for naturally aspirated or 4.0L for forced induction (turbo/supercharged). This means the 6.2L V8 found in the road going Corvette is downsized to 5.5L to meet the rules, although the SRT Viper GTS-R was granted a special waiver to run an 8.0L V10 in 2015.
When it comes to the construction of the car; carbon fiber, titanium and magnesium are banned except for special parts like spoilers or wheels. Cars with carbon cockpits (that are not directly attached to the suspension) are permitted. The minimum weight is 1,245 kg (2745 lbs) including driver, fuel, helmet and liquids. Cars must have working lights and windshield wipers at all times. Four-wheel drive is banned while engine-based traction control is allowed. Transmissions are limited to six forward gears. All cars must also have rear-view cameras in addition to side mirrors.
Overall, the technical regulations are focused on keeping LM GTE cars relatively close to road cars in terms of parts and dimensions. Aerodynamic devices such as wings, diffusers and splitters are heavily regulated. There are also minor requirements that are carried over from the earlier era of Le Mans, such as requiring at least 150 cubic centimeters of luggage space. The homologation rules are set by the ACO for the Le Mans 24 Hours and are then carried into the respected US, European and Asian championships, so that race teams are not required to build multiple cars for different series.
The only changes to these rules are either from the race team due to special circumstances such as the Porsche 911 GT3 RSR was allowed to relocate the engine from the rear to be mid mounted. This was in response to the rear mounted engine on the Porsche restricted the size of their rear diffuser, therefore the competition were able to utilize full size rear diffusers essentially giving an advantage. Any other changes are due to Balance of Performance (BoP) which is a system to ensure that the field of mixed cars are equal in performance. This is what makes sports car racing unique as the cars from their respective manufacturers can all differ so much potentially giving one brand an advantage. For example a front engined BMW may struggle against a mid engined Ferrari in terms of weight, balance or aerodynamic advantages, so the BoP counters this by taking all the cars lap times from practice and sometime qualifying and then adjustments are made to even the field of cars out. This is done by slowing the fastest cars down and speeding up the slower cars via adding/removing weight ballast or increasing/decreasing the air intake (known as air restrictor) for the engine altering horsepower output. For forced induction engines BoP can restrict or even reduce the turbo pressure, which again will alter the horsepower output. BoP has been subject to controversy due to on occasions getting their adjustments wrong causing some cars to have a notable advantage. This is usually due to race teams purposely setting slower lap times (also known as sandbagging) to ensure there is no additional BoP added for the race or even allowing to have some restrictions removed.
C8.R vs C8 Stingray
Chevrolet says the Corvette C8.R uses more parts with its production equivalent than any other Corvette race car to date. With around 100 parts shared between the road legal C8 Stingray and the C8.R race car, the list of changes from road car to race car is still extensive:
Pratt & Miller start off with a Corvette C8 chassis fresh out of the Bowling Green plant. The convertible aluminum frame features vacuum die-castings at all four corners to support the suspension mounts that are the same on both the race car and the road car. The chassis itself, however, has been stiffened and lightened with racing in mind and a steel roll cage is welded to the frame increasing rigidity and adding driver safety.
The road-legal Corvette C8 Stingray is powered by the familiar 6.2-liter pushrod V8 dubbed by GM as the LT2. The LT2 powerplant produces 495 hp and 470 lb-ft of torque when equipped with the optional performance exhaust. The 5.5-liter DOHC V8 engine that powers the C8.R produces 500 horsepower and 480 lb-ft of torque @ 7,400rpm due to the air restrictors mandated by a power limit for the GTLM class the C8.R competes in. Without these restrictors the power output would be considerably higher. These two engines are very different in architecture due to the V8 in the race car using dual overhead cams and a flat plane crankshaft, which allows the race motor to rev much faster and higher. Whereas the LT2 retains the same basic overhead-valve design that GM small blocks have used for decades. The LT2s cross-plane crank shaft means it won’t rev as high as the race car meeting its redline at 6,600rpm. The small block Chevy V8 has become synonymous with creating low end torque despite the peak torque on the LT2 arrives at relatively high 5,150 RPM. The flat plane crank, DOHC design of the engine in the race car will mean that low end torque will be less but a lot of the power will come at the higher RPM. This decision takes advantage of the demands of motorsports typically keeping engines in the high RPM range due to gearing and wide open throttle application being very common. Having a motor that produces its peak power and torque at high rpm means that the motor will be kept in the power band within a race environment.
“A flat-plane crank doesn’t have counter weighting on the crankshaft, that gives you better response, and those are the primary reasons why you would do a flat-plane crank,’ said Ed Piatek, the C8’s Chief Engineer.
A flat plane crankshaft does have its drawbacks due to an increased lateral vibrations in place of counter weighting. This can cause a lot more components to come loose or even break.
“We have seen things in testing that we have had to address due to the vibration, but
nothing fundamental,” Ben Johnson, Vehicle Integration Engineer at Corvette Racing underlined “things were coming loose that we never thought about on the C7.” Some of the vibrations, especially from the gearbox, have been dampened via the strengthened, shorter prop shaft.
The only similarities between the two V8 motors is from both taking advantage of direct injection and dry sump oiling systems.
When it come to the transmissions, the two cars are very different. The 2020 Corvette C8 Stingray is the first Corvette to come from the factory with an eight-speed dual-clutch transmission built by Tremec as standard. The duel-clutch design allows for very fast, consistent gear changes in both manual and automatic mode. However the transmission in the C8.R race car shifts even faster and more accurately thanks to using a six-speed sequential racing gearbox built by Xtrac. The British transmission company Xtrac provide gearboxes to almost the enter 50+ field of race cars at the 24 Hours of Le Mans including the top LMP1 class. Xtrac could be argued as the best race transmission provider as their gearboxes are used in multiple disciplines of motorsports from F1 to Rally. The C8.R needs this reliability especially when competing in gruelling 24 hour endurance races. The new mid engined layout forces the transmission to be located further back than previous Corvette race car. Xtrac therefore built a bespoke very compact transaxle for the C8.R in order to create room for a larger rear diffuser
The C8 Stingray road car and the C8.R race car share the same wheelbase of 107.2 inches just like the previous C7 Corvette and C7.R Race car, but unlike the previous generation the overall length is the same between the road car and race car coming in at 182.3 inches. This is thanks to the new mid engine design of the C8 allows for a much smaller redesigned front splitter compared to the C7.R large extended front splitter. The stance of the race car is a lot wider and lower than the road car as the C8.R sits 4.6 inches wider the road going C8 Stingray thanks to huge racing slicks housed under aggressively flared fenders. Keeping the center of gravity as low as possible the C8.R race car sits 3.4 inches lower than the standard C8 Corvette.
Weight plays a major factor in motorsports and although the GTLM class the C8.R competes in is restricted to a minimum weight of 2745 lbs the C8.R is far lighter than the road equivalent. The C8 Stingray with the Z51 performance package weighs in at 3587 lbs, which is a gain of 151 pounds over the previous generation C7 Stingray. Chevrolet quotes a weight of 2733 lbs for the C8.R, which is slightly heavier than the previous C7.R. This is the dry weight, once driver and fluids are added the weight exceeds the 2745 lbs minimum that the rules mandate. The lighter weight of the C8.R is accomplished by stripping out a lot of the luxuries the road car has such as: sound dampening, carpets, roof liner, GPS, center console, stereo and air bags. Glass windows are replaced by polycarbonate windows and the two heated, electric seats are replaced by one carbon fiber racing bucket seat. The race car however does have air conditioning but it is not the same heavy, power sapping unit from the road car but replaced with a super lightweight unit that barley uses power from the engine designed by Pratt & Miller back in 2005 when drivers were suffering under the extremely high cabin temperatures. The A/C unit in the race car is located in the vacant passenger side of the cabin and provide cool air via a hose connected to the drivers helmet.
Aerodynamics play an extremely important role in motorsports, but it is also very strictly monetized by the governing bodies to ensure no team is gaining an advantage. The road car has to comply with road safety standards and keep practicality in mind. Race engineers get a lot more freedom to help produce downforce and reduce drag on the C8.R but Pratt & Miller could not just simply add on the biggest wing they could build to the C8.R. Height, angle, mounting position, end plates and gurney flap all need to meet regulations. GM take this into consideration when building a new generation Corvette and even approach Pratt & Miller beforehand to work together to building a car that can take advantage of aero on the track around the rules.
The front splitter took a new design then previous generation Corvette race cars. The new splitter features more of a concealed look by channeling air through small veins located in the bottom, center of the front facia. Dive planes/canards are added to the sides of the front facia which help direct air over the front of the car, reducing lift. Cutouts are added on the fenders behind the front wheels allowing the turbulent air generated by the wheels at high speed within the fenders to escape, greatly reducing front end lift.
The underneath of the race car is completely flat and covered allowing the air travelling under the car to be directed to rear diffuser. By using large veins which help take advantage of the venturi effect by channeling the low pressure air from under the car therefore sucking the rear of the car down to ground adding more rear stability and grip. The C8.R features the exhausts above the rear diffuser thanks to the mid engine layout opposed to the side exit exhausts found on all previous Pratt & Miller Corvette race cars. The look of the rear diffuser is similar to the previous C7.R diffuser however this time it is slightly larger. When the C7.R debuted in 2014 the rules forced a flat, horizontal diffuser until the rule changes in 2016 made to the GTE/GTLM class allowed for a much bigger aero package increasing the size of the front splitter, side skirts and rear diffuser. Unfortunately Pratt & Miller were restricted to how much they could increase the rear diffuser as it would have required an extensive sub-frame redesigns that Corvette Racing decided against since the C8.R was in its beginning stages of development.
“Everyone pushes the wing as far back and high up as they can and then you section the rear fascia at the maximum line to help rear downforce and extraction,” said Ben Johnson,
The road-going C8 Stingray makes 400 lbs of downforce @ 180 mph when equipped with the Z51 Performance Package, the C8.R race car will produce a vastly higher amount of downforce however Corvette Racing won’t quote the exact amount of downforce the C8.R produces, but they say the C8.R generates ten percent more downforce than the previous generation C7.R that it replaces.
The road-legal C8 Stingray is equipped with 13.3-inch steel rotors up front and 13.8-inch steel rotors in the rear. Both front and rear brakes use four-piston calipers. The C8.R race car brakes are greatly upgraded to meet the demands of endurance racing by using Alcon Racing six-piston monoblock calipers in the front and rear that also helps to save weight. The GTLM class rules mandate that all cars must use steel rotors, but these rotors are also greatly increased in size measuring 15.35 inches up front and 14.0 inches in the rear. The race car rotors are vented and slotted to help keep temperatures down and feature a quick release function allowing Corvette Racing to switch worn brake rotors within seconds during 24 hour endurance races. The brakes on the C8.R use a conventional, manual setup opposed to the brake-by-wire setup on the C8 Stingray road car.
“This [new] car has more rear weight bias [than the C7.R], and you run more rear brake than on the C7 so they have grown in size, and we have a much bigger rotor in the front,” said Johnson. Corvette Racing previously partnered with AP Racing for the brakes on the C7.R.
The road legal C8 Stingray switched up the suspension setup from the composite leaf spring setup found on the previous generation Corvettes by moving to a double wishbone, coilover passive spring and damper setup, that can be upgraded to Chevrolets magnetorheological dampers. The suspension in the C8.R race car uses a short/long arm (SLA) double-A-arm setup, fabricated steel upper and lower control arms, featuring fully adjustable coil-over shock absorbers and spring rates. Being fully adjustable, the suspension setup can be completely customized to maximize mechanical grip at different circuits. For example the dampers are set very soft at a bumpy track like Sebring and are stiffened for the high banks of Daytona.
The C8 Stingray sits on 19 inch front wheels and 20 inch rear wheels wrapped in Michelin Pilot Sport 4S three season tires. The partnership Corvette and Michelin have is thanks to the Corvette Racing program as the race cars have been using Michelin race tires since 2004. The wheels and tires on the C8.R race car differ by meeting the GTLM rules. The race car uses 18 inch front and rear BBS wheels with a single center locking wheel nut, allowing for fast and easier tire changes. The smaller diameter rim allows the tire to have a bigger sidewall, which the tire manufacturers take advantage of to optimize the highest level of grip. The race car uses Michelin racing slick tires offering four different compounds including grooved tires for wet weather racing. The race tires are much wider than the road legal C8 Stingray by 4 inches on the front and 2 inches wider in the rear.
After Chevrolet unveiled the new C8 Stingray, they went into detail about the specs of the LT2 motor. The LT2 would be an evolution of the 6.2 liter LT1 V8 found in the seventh generation Corvette. Chevrolet took pride in announcing the C8 Stingray would be the world’s only current naturally aspirated, 6.2L pushrod V8, mid engined sports car, so many expected the race car to continue the tradition and be using the same engine platform only adapted for motorsports. But a few people had seen a spy video released months prior of a camouflaged C8.R race car practicing at Sebring during the night. The biggest controversy of the video would be the sound coming from the exhausts. The ground pounding thunder of the V8 that Corvette Racing had become famous for had been replaced by a flatter sounding higher pitched scream resembling that of a flat plane V8 found in Ferraris and McLarens. People speculated that the youtube video could have been edited or a fake, so when the race car fired up for the first time in public at the unveiling, it proved the video was accurate. This would later be confirmed when the #4 C8.R would run an exhibition lap at Road Atlanta prior to the Petit Le Mans in October 2019. These changes would prove to be one of the biggest steps in Corvette Racing history, whereas the previous three generation Corvette race cars had all been updated evolutions of a trusted front mounted pushrod V8, the new C8.R would be a different engine layout with an all new engine design. Chevrolet have kept their cards close to their chests with the motor under the hood of the C8.R only to say it’s a 5.5 liter DHOC (Double Over Head Cam) V8. But history has taught us that Corvette Racing have traditionally based their race cars on the Z06 models. This has created a frenzy into the public asking will the C8 Z06 be equipped with an naturally aspirated, flat plane crank, DHOC V8? This is backed by the championship homologation rules mandates that the race engine must be based on a road going engine in at least 300 vehicles.
The unveiling also revealed a new livery for the Corvette Racing team. Since the year 2000 Corvette Racing has always sported a predominantly yellow color scheme (besides some special edition paint schemes). The new C8.R race car revealed a new livery of silver with yellow accents. Chevrolet said this was a tribute inspired by GM design legend Bill Mitchell who paid out of his own pocket to see a Corvette race in the very late 1950s and early 1960s. Originally, this Stingray race car was painted red but towards the end of its racing career, it was painted in silver at Mitchell’s request due to the famous designer being a huge fan of the ’Silver Arrows’, the German Grand Prix cars built by Auto Union and Mercedes-Benz in the 1930s. Later pictures would reveal the sister #3 race car would wear a reverse color scheme being wrapped in Velocity Yellow with the accents in silver.
January 25th 2020 would mark the debut race for C8.R as it competed in the Rolex 24 Hours at Daytona that would kick start the 2020 season for the IMSA WeatherTech SportsCar Championship. The C8.R would continue to compete like its predecessor in the GTLM class against some of the worlds biggest manufacturers such as Ferrari, BMW and Porsche. Despite many hours of testing most race cars debut races usually end in failure or in a low position commonly related to reliability of the new components, therefore many fans had low expectations for the new C8.R debut race. However the #3 C8.R would prove to be the fastest GTLM car in the night time practice, running 0.6 seconds faster than the second placed #912 Porsche 911. When it came to qualifying Porsche would lock out the front row with the #911 Porsche 911 placing on pole and the sister #912 Porsche 911 placing in second. The second row of the grid would be locked out by the two Corvettes with the #3 C8.R qualifying only three tenths behind the pole sitting Porsche and the #4 C8.R starting in forth. The two BMW M8s would take fifth and sixth on the grid with the Ferrari 488 GTE having the slowest qualifying time started from seventh. When it came to the race the #3 C8.R was able to take the lead during ninth hour mark but the sister #4 car during the tenth hour would make its way to the garage with an oil leak and wouldn’t return for many hours. There was many back and forth, jostling for positions but the Porsches would prove to be too fast for the competition, until the #25 BMW took the lead in the late hours of the race and held off the Porsches to take the victory. The #3 Corvette C8.R would finish fourth in its debut race and the #4 C8.R would finish last in its class due to the lengthy time in the garage.
Due to COVID-19, the IMSA WeatherTech SportsCar Championship would be paused after the Rolex 24 at Daytona and would later restart the season in July with a return to Daytona for a two hour and 40 minute race. The C8.R would dominate and take its first win with the #3 car and the #4 sister car finishing fifth.
The third race would take place at Sebring for another two hour and 40 minute race with the traditional 12 hour endurance race being moved to November due to COVID-19. Corvette Racing would lock down the top steps of the podium taking first and second place with the #4 C8.R finishing ahead of the #3 C8.R.
Race number four took place at Road America and yet again Corvette Racing took first and second place with the #3 car finishing on top.
The fifth race of the season took place at VIR (Virginia International Raceway) with Corvette Racing took another victory making it three in a row for the team with the #3 car finishing first and the #4 car finishing fourth behind the two Porsches.
Race six at Road Atlanta would be a six hour endurance race and the Corvette Racing would fall short with the #4 C8.R finishing second to #25 BMW M8 and the #3 car finishing in fifth.
Dominance would resume for Corvette Racing during the seventh race of the season at Mid-Ohio where the #3 C8.R took the victory with the #4 C8.R in second after a two hour and 40 minute race.
The #3 C8.R would take the next victory at Charlotte Motor Speedway after a one hour and 40 minute race and the #4 C8.R finished fourth.
October would feature the traditional Ten hour endurance Petit Le Mans race at Road Atlanta with the #3 C8.R taking second behind the #911 Porsche 911 and the #4 C8.R finishing in fourth behind the #24 BMW M8.
Race ten took place at Leguna Seca for another two hour and 40 minute race with the #912 Porsche 911 taking the victory and the two Corvette’s taking second and third with the #3 C8.R finishing ahead of the #4 C8.R.
The final race of the 2020 season would be the 12 Hours of Sebring postponed from February to November. Corvette Racing failed to finish on the podium breaking a nine race top three streak with the #3 C8.R finishing in fifth and the #4 C8.R finishing in sixth. Despite the disappointing result at Sebring Corvette Racing would secure the manufacturers championship and the drivers championship proving the most dominate debut season for a new Corvette under Corvette Racing since 2005 with the C6.R GT1.
|Model:||2020 Chevrolet Corvette C8.R|
|Body Style:||2-door coupe|
|Layout:||Mid-engined, longitudinal powertrain placement|
|Driveline:||Rear wheel drive|
|Manufacturing Location:||Pratt & Miller, New Hudson, Michigan, USA|
|Engine:||LT5.5, 5.5L V-8|
|Displacement (cu in / cc):||335 / 5500|
|Valvetrain:||Double Overhead Cam, four valves per cylinder|
|Fuel Delivery:||Direct Injection|
|Horsepower (hp / kW @ rpm):||500 / 373 @ 7,400|
|Touque (lb ft / Nm @ rpm)||480 / 651 @ 7,400|
|Fuel:||VP Racing Fuel|
|Transmission:||Compact Xtrac Six-Speed Sequential|
|Front:||Short/long arm, double-A-arm setup, lower control arms, and adjustable coil-over shock absorbers and springs|
|Rear:||Short/long arm, double-A-arm setup, lower control arms, and adjustable coil-over shock absorbers and springs|
|Front Rotors:||Steel vented and slotted 15.35-inch monoblock rotors|
|Rear Rotors:||Steel vented and slotted 14.0-inch monoblock rotors|
|Front Calipers:||Alcon Racing six-piston monoblock calipers|
|Rear Calipers:||Alcon Racing six-piston monoblock calipers|
|Tire:||Michelin Racing Slicks|
|Tire Compound:||Soft, Medium, Hard and Wet|
|Wheels:||BBS six spoke-split end, single center locking wheel nut|
|Front wheel size:||18 inch x 11.5-inch|
|Rear wheel size:||18 inch x 12.5-inch|
|Front tire size||30/68-R18|
|Rear tire size:||31/68-R18|
|Wheelbase (in / mm):||107.2 / 2,723|
|Overall length (in / mm):||182.3 / 4,630|
|Overall width (in / mm):||80.7 / 2,050|
|Overall height (in / mm):||45.2 / 1,148|
|Dry weight (lbs / kg):||2,733 / 1239.6|