Fpc
Thread Starter
Drifting
Joined: Aug 2018
Posts: 1,274
Likes: 719
Fpc
As i was looking through my records I found this from GM Authority?
Anyway it is interesting
Powertrain
The road-legal Corvette C8 Stingray is powered by the familiar 6.2-liter pushrod V8 dubbed by GM as the LT2. The LT2 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, allowing the race motor to rev much faster and higher. The LT2 retains the same basic overhead-valve design that GM small blocks have used for decades and with its cross-plane crank shaft it cannot 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 the regularity of wide open throttle application. Having a motor that produces its peak power and torque at high rpm means that the motor will be held in the power band within a racing environment.
The Chief Engineer of the C8, Ed Piatek mentioned that the primary reasons behind the use of a flat-plane crank, is that it does not require counter weighting on the crankshaft, which results in better response, however a flat plane crankshaft does have its drawbacks. Due to an increased lateral vibrations in place of counter weighting a lot more components can come loose or even break.
Vehicle Integration Engineer at Corvette Racing, Ben Johnson reported that during testing they had to address issues due to the vibrations from the flat-plane crank. The team witnessed components were coming loose that they never thought about on the C7. The result was some of the vibrations, especially from the gearbox, needed to be dampened via a strengthened and shorter prop shaft.
The only similarities found between the LT2 V8 found in the C8 Stingray and the LT5.5 of the C8.R is both taking advantage of direct injection and dry sump oiling systems.
Transmission
The transmissions between the production C8 and the C8.R 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 across 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.
Anyway it is interesting
Powertrain
The road-legal Corvette C8 Stingray is powered by the familiar 6.2-liter pushrod V8 dubbed by GM as the LT2. The LT2 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, allowing the race motor to rev much faster and higher. The LT2 retains the same basic overhead-valve design that GM small blocks have used for decades and with its cross-plane crank shaft it cannot 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 the regularity of wide open throttle application. Having a motor that produces its peak power and torque at high rpm means that the motor will be held in the power band within a racing environment.
The Chief Engineer of the C8, Ed Piatek mentioned that the primary reasons behind the use of a flat-plane crank, is that it does not require counter weighting on the crankshaft, which results in better response, however a flat plane crankshaft does have its drawbacks. Due to an increased lateral vibrations in place of counter weighting a lot more components can come loose or even break.
Vehicle Integration Engineer at Corvette Racing, Ben Johnson reported that during testing they had to address issues due to the vibrations from the flat-plane crank. The team witnessed components were coming loose that they never thought about on the C7. The result was some of the vibrations, especially from the gearbox, needed to be dampened via a strengthened and shorter prop shaft.
The only similarities found between the LT2 V8 found in the C8 Stingray and the LT5.5 of the C8.R is both taking advantage of direct injection and dry sump oiling systems.
Transmission
The transmissions between the production C8 and the C8.R 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 across 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.
Last edited by Kodiak Bear; Jul 16, 2021 at 05:58 PM.
Race Director
Joined: Nov 2017
Posts: 12,759
Likes: 10,655
From: Prosper TX/Austin TX
2020 C6 of the Year Winner - Modified
And basically the same relationship between the C7 & C7.R engine - which was also 5.5l and used restrictors to keep the power down. And just as that engine didn’t go into the C7 Z06, it makes no sense for the C8.R engine (or a variation of it) to go into a C8 Z06.
https://www.corvsport.com/c7-r-anatomy-race-car/
https://www.corvsport.com/c7-r-anatomy-race-car/
Melting Slicks
Joined: Aug 2003
Posts: 2,240
Likes: 2,171
From: Cary NC
It's an older article - but as is usually the case with GM Authority, they twisted a few things around and misconstrued others as related to the engine. Keep in mind also they cherrypicked a few of Ed's words, and he was referring to the C8R and not necessarily to a street flat-plane application.
Le Mans Master
Joined: Aug 2000
Posts: 5,529
Likes: 1,943
From: Austin Texas
The Chief Engineer of the C8, Ed Piatek mentioned that the primary reasons behind the use of a flat-plane crank, is that it does not require counter weighting on the crankshaft, which results in better response, however a flat plane crankshaft does have its drawbacks. Due to an increased lateral vibrations in place of counter weighting a lot more components can come loose or even break.
