C8 Z06 670HP NA FPC!!
- Thread starter Z06
- Start date
Some detailed engine specs are rolling in:
The engine is rated at 670 horsepower and 460 pound-feet of torque, with the horsepower peaking at 8400 rpm, right near the 8600-rpm fuel cut. That Ferrari V-8s also make peak power right at redline is no coincidence. In the LT6, more revs mean more power, and the engineering team will use every last rpm it can.
In an automotive world obsessed with electrification and efficiency, it's bold for GM to develop a new engine with a short stroke and a fat bore. Cylinder dimensions are 104.25 millimeters by 80.0, netting a displacement of 5.5 liters. The compression ratio is 12.5:1. And for the engine nerds: The brake mean effective pressure is in excess of 1400 kilopascals.
The C8 team could have easily installed a pushrod V-8 with a blower on top, but a supercharged engine doesn't have the character of a flat-plane-crank V-8. During development, GM traded its Ferrari 458 for the turbocharged 488, and the team agreed with our assessment that some magic was lost. So they bought another 458.
Flat-plane cranks aren't a perfect solution, however. (Owners of Ford's Mustang Shelby GT350, with its high-revving 5.2-liter V-8, will relate.) They shake—a lot. So much that during LT6 development, an oil filter backed itself off on a test stand. Engineers suspected a tech hadn't tightened it, but video evidence uncovered no wrongdoing. The solution was to switch from a screw-on to a cartridge filter.
To keep those forces at bay, titanium connecting rods and intake valves hold reciprocating mass to a minimum. Exhaust valves are filled with sodium. All 32 valves are fitted with two springs each to prevent valve float at high rpm. Direct-acting finger followers have a diamond-like coating and are shimmed during assembly. "Lash for life," says Jordan Lee, GM global chief engineer for small-block engines.
The CNC-machined DOHC heads make the engine bigger than its pushrod siblings. In the C7 engine, height and width had tighter limitations because increasing either wasn't possible without affecting the hood height and footwell width. With the engine behind the cabin, those dimensions are less of a concern. And considering that the C8 was designed around an engine of a specific length, we understand why engineers kept the small-block's bore spacing.
The block has what GM calls a dedicated lower crankcase. It's similar to how Ferrari does dry sumps, with each crank journal residing in a sealed bay. There are six oil scavenge pumps: one in each bay and one in each head.
The intake features two plenums, two 87-mm throttle bodies, three valves that connect the plenums, and eight beautiful trumpets. Those crossover valves tune the intake to optimize both high- and low-rpm operation.
Direct fuel injection is the obvious choice. But instead of injectors squirting fuel on the intake side of the heads near the valley of the vee, the injectors are located between the exhaust valves, a design cribbed from Chevy's Indy V-6. Squirting fuel toward the incoming intake air promotes tumble (the motion and mix of air and fuel). More tumble improves burn.
Flat-plane-crank V-8s are a visceral thing. The intake sound reminds us of the sounds of our youth and draws in our adult selves like a siren song. The first time you hear a C8 Z06 start, your head will snap around like a kid getting called in to dinner on a warm summer night. —K.C. Colwell
The engine is rated at 670 horsepower and 460 pound-feet of torque, with the horsepower peaking at 8400 rpm, right near the 8600-rpm fuel cut. That Ferrari V-8s also make peak power right at redline is no coincidence. In the LT6, more revs mean more power, and the engineering team will use every last rpm it can.
In an automotive world obsessed with electrification and efficiency, it's bold for GM to develop a new engine with a short stroke and a fat bore. Cylinder dimensions are 104.25 millimeters by 80.0, netting a displacement of 5.5 liters. The compression ratio is 12.5:1. And for the engine nerds: The brake mean effective pressure is in excess of 1400 kilopascals.
The C8 team could have easily installed a pushrod V-8 with a blower on top, but a supercharged engine doesn't have the character of a flat-plane-crank V-8. During development, GM traded its Ferrari 458 for the turbocharged 488, and the team agreed with our assessment that some magic was lost. So they bought another 458.
Flat-plane cranks aren't a perfect solution, however. (Owners of Ford's Mustang Shelby GT350, with its high-revving 5.2-liter V-8, will relate.) They shake—a lot. So much that during LT6 development, an oil filter backed itself off on a test stand. Engineers suspected a tech hadn't tightened it, but video evidence uncovered no wrongdoing. The solution was to switch from a screw-on to a cartridge filter.
To keep those forces at bay, titanium connecting rods and intake valves hold reciprocating mass to a minimum. Exhaust valves are filled with sodium. All 32 valves are fitted with two springs each to prevent valve float at high rpm. Direct-acting finger followers have a diamond-like coating and are shimmed during assembly. "Lash for life," says Jordan Lee, GM global chief engineer for small-block engines.
The CNC-machined DOHC heads make the engine bigger than its pushrod siblings. In the C7 engine, height and width had tighter limitations because increasing either wasn't possible without affecting the hood height and footwell width. With the engine behind the cabin, those dimensions are less of a concern. And considering that the C8 was designed around an engine of a specific length, we understand why engineers kept the small-block's bore spacing.
The block has what GM calls a dedicated lower crankcase. It's similar to how Ferrari does dry sumps, with each crank journal residing in a sealed bay. There are six oil scavenge pumps: one in each bay and one in each head.
The intake features two plenums, two 87-mm throttle bodies, three valves that connect the plenums, and eight beautiful trumpets. Those crossover valves tune the intake to optimize both high- and low-rpm operation.
Direct fuel injection is the obvious choice. But instead of injectors squirting fuel on the intake side of the heads near the valley of the vee, the injectors are located between the exhaust valves, a design cribbed from Chevy's Indy V-6. Squirting fuel toward the incoming intake air promotes tumble (the motion and mix of air and fuel). More tumble improves burn.
Flat-plane-crank V-8s are a visceral thing. The intake sound reminds us of the sounds of our youth and draws in our adult selves like a siren song. The first time you hear a C8 Z06 start, your head will snap around like a kid getting called in to dinner on a warm summer night. —K.C. Colwell
I love it. Would love to get on after a few years especially since I have a boosted car already.
From Hotrod
.....As you all know, the C8's mill resides behind the driver, a huge change for Corvette, but one that provides a ton of performance and handling benefits. Chevrolet decided to pull out all the stops on the Z06's engine. What's so cool about the LT6? Well, tops of that list would be the LT6's flat-plane crank (as opposed to the LS and previous LT's cross-plane crank). While the crank gets lots of attention there's far more to this LT6 than just a unique (for an American V-8) crank. Things like an all-new aluminum block that still has the small-block family's signature 4.4-inch bore spacing. Or the new dual-overhead cam layout with fully CNC-machined combustion chambers and intake ports. There's also the mechanical "finger follower" valvetrain and dual-coil valve springs with titanium intake and sodium filled exhaust valves. If that sounds familiar, then you most likely remember those valves from the LS7 engine. Well, they borrowed from the near perfection of that engine with forged pistons and titanium connecting rods as well.
Add this all up and you end up with the most powerful naturally aspirated factory engine ever stuffed into a Corvette: 670 hp at 8,400 rpm (with an 8,600-rpm redline) and 460 lb-ft of twist at 6,300 rpm should be enough to get anyone's attention. And, no, the 8,600-rpm part wasn't a typo, thanks to the super-lightweight rotating guts, short stroke, and oversquare cylinders.
While this LS6 seems "all new" and fresh on the scene the truth is that a version of this engine has been powering the Corvette C8.R race cars since 2019. All that on track testing helped engineers refine the LT6's performance and durability. When we first heard the C8.R and figured out it was running a flat plane crank we speculated, over a year and a half ago, that due to the rules governing Chevrolet Racing that GM would have to field this engine in a production car and our bets were on the Z06. We were right, and you can read that prediction here.
f you have a keen eye, and look around the engine bay of the Z06, you'll find little rocket ships cast or molded into various parts. Was this an inside joke about how the new 2023 Corvette Z06 will be a rocket? Well, that would be a good guess, but really it was the design team giving the LT6 engine family the nickname Gemini. This is due to its use of twin 87mm throttle bodies, twin cams, twin high-pressure fuel pumps, and other pairs of cool parts. Nice to see they are still having fun over at GM.
The new 11-liter active split intake manifold is another engineering wonder. Active? Yeah, you see due to the firing order of the new crank there were performance benefits from a physics deal called resonance supercharging. This volumetric efficiency is leveraged by a series of three valves that connect the two intake plenums. These open in different combinations to vary the effect the pressure waves within the plenum or between the two plenums. When one of the 32 valves closes it generates a pressure wave that travels back up the intake runner. If you time it "just right" that wave reflects back down while the intake valve is open. This returning wave rams a bit more air into the party, which makes a bit more power. If you want to learn more then Google "Helmholtz Resonance Effect," which is the same principal.
A cool new engine necessitated a cool new exhaust. The hard part with a flat-plane crank is that is can sound like two angry four-cylinder engines next to each other; it's a problem that can't be solved with a simple X-pipe or other crossover tube. To get the sound right, a process that took two years, they started with the unique four-into-two-into-one stainless steel exhaust headers. Equal-length pipes feed into a unique and highly tuned system which winds through mufflers, stuffed in the corners of the car, and exits out the middle through parabolic reflectors which sends the LT6 engine music toward the Z06's cabin. Like other GM offerings the Z06 has an active exhaust which can be anything from crazy loud to stealthy quiet. The result a Ferrari-like scream, but with a somewhat deeper tone. The tuning wizards at Chevrolet set a delay for the direct fuel injectors to encourage a few extra burps and pops on overrun, but only while your foot is moving the throttle. After all, too much of good think is sometimes still too much.
Fun fact: When the pandemic shut GM down all the work stopped, but the computers kept rehashing the exhaust system designs until they determined the center-exit solution. The sound was loved by all but redesigning the rear fascia to house the centrally mounted reverse-megaphone tips cost millions, to us it was worth every penny.
How big of a departure from the "norm" or previous LS and LT engines? Well, aside from what we've already mentioned how about how the starter being mounted in the rear of the LT6's valley beneath the intake while the alternator lives in the same valley but to the front of the mill. The valley is pretty crowded since it also houses the twin high-pressure cam-driven (optimized for 9,000-rpm operation) fuel pumps. Another oddity compared to previous engines are the injectors which side mounted under the exhaust valves. This not only made room for the huge active intake, but it also mixes the fuel better.
The LT6 engine is hand-assembled by master engine builders at the Performance Build Center within the Bowling Green Assembly Plant in Kentucky. Builders use precision tooling and hand fit pieces of the engine to meet Chevrolet's exact specifications. Each engine features a plaque on the intake manifold with the signature of the technician who crafted it from start to finish. A visit to this plant is high on our list of things to do.
Oil is life and to an engine designed for hard road course life a robust oiling system is of upmost importance. In this area, the LT6 engine learned a lot from it's C8.R race-bred cousin. Each piston pair is hermetically sealed off from the other pistons so that the air under the pistons simply back and forth with minimal losses from pumping. The six-bay oil pump, that runs the length of the LT6, scavenges each bay, along with the cylinder heads, and takes 14 hp to operate. The system uses 10 quarts of 5W50 and the rather large cooler is housed in the driver side rear intake. According to Chevrolet track day temps should stay around 250 to 265 degrees.
There are two crank designs available when picking one for your next V8 project: cross- and flat-plane. For the most part cross-plane cranks dominate, especially in American V-8 engines, while flat-plane cranks typically show up in high-end Euro exotics and full-on race cars. Cross-plane cranks give American muscle its distinctive rumble while flat-plane cranks have a tell tail high-rpm whine. But, there's more to these cranks than just their exhaust notes.
Flat-plane cranks, in V-8 and V-12 engines, used to be fairly rare and only seen in uber-expensive super- and hypercars. They're the reason you can always tell a Ferrari is ready to crest the hill at a track day. Just like the name states a flat-plane crank has all its crank pins in a single, flat plane. This is much like an inline 4-cylinder crank, but with more space for more rods.
Flat-plane cranks, no matter what firing order they have, will always alternate from bank to bank. This yields optimum exhaust scavenging and thus doesn't require the more complex header primaries that have to cross over from one bank to the other. Due to their design they don't need huge counterweights, which is why they weigh less and rev up so quickly. The downside is that they suffer from secondary vibrations.
Chevy solved the vibration issue with LT6 engine by minimizing piston speeds, by opting for a large 4.11-inch bore and short 3.15-inch stroke. The result is a 103-mph peak piston speed at redline (for example a the 5.2L in the Shelby Mustang has 114 mph piston speed). Vibration was also helped by the use of titanium piston rods from Austria-based Pankl Racing Systems. Even the aluminum harmonic balancer helps in the battle to solve flat-plane crank vibrations. There are still some vibrations, but nothing detrimental to the car, the LT6, or the Corvette Z06's mission to be baddest Corvette ever built.
.....As you all know, the C8's mill resides behind the driver, a huge change for Corvette, but one that provides a ton of performance and handling benefits. Chevrolet decided to pull out all the stops on the Z06's engine. What's so cool about the LT6? Well, tops of that list would be the LT6's flat-plane crank (as opposed to the LS and previous LT's cross-plane crank). While the crank gets lots of attention there's far more to this LT6 than just a unique (for an American V-8) crank. Things like an all-new aluminum block that still has the small-block family's signature 4.4-inch bore spacing. Or the new dual-overhead cam layout with fully CNC-machined combustion chambers and intake ports. There's also the mechanical "finger follower" valvetrain and dual-coil valve springs with titanium intake and sodium filled exhaust valves. If that sounds familiar, then you most likely remember those valves from the LS7 engine. Well, they borrowed from the near perfection of that engine with forged pistons and titanium connecting rods as well.
Add this all up and you end up with the most powerful naturally aspirated factory engine ever stuffed into a Corvette: 670 hp at 8,400 rpm (with an 8,600-rpm redline) and 460 lb-ft of twist at 6,300 rpm should be enough to get anyone's attention. And, no, the 8,600-rpm part wasn't a typo, thanks to the super-lightweight rotating guts, short stroke, and oversquare cylinders.
While this LS6 seems "all new" and fresh on the scene the truth is that a version of this engine has been powering the Corvette C8.R race cars since 2019. All that on track testing helped engineers refine the LT6's performance and durability. When we first heard the C8.R and figured out it was running a flat plane crank we speculated, over a year and a half ago, that due to the rules governing Chevrolet Racing that GM would have to field this engine in a production car and our bets were on the Z06. We were right, and you can read that prediction here.
f you have a keen eye, and look around the engine bay of the Z06, you'll find little rocket ships cast or molded into various parts. Was this an inside joke about how the new 2023 Corvette Z06 will be a rocket? Well, that would be a good guess, but really it was the design team giving the LT6 engine family the nickname Gemini. This is due to its use of twin 87mm throttle bodies, twin cams, twin high-pressure fuel pumps, and other pairs of cool parts. Nice to see they are still having fun over at GM.
The new 11-liter active split intake manifold is another engineering wonder. Active? Yeah, you see due to the firing order of the new crank there were performance benefits from a physics deal called resonance supercharging. This volumetric efficiency is leveraged by a series of three valves that connect the two intake plenums. These open in different combinations to vary the effect the pressure waves within the plenum or between the two plenums. When one of the 32 valves closes it generates a pressure wave that travels back up the intake runner. If you time it "just right" that wave reflects back down while the intake valve is open. This returning wave rams a bit more air into the party, which makes a bit more power. If you want to learn more then Google "Helmholtz Resonance Effect," which is the same principal.
A cool new engine necessitated a cool new exhaust. The hard part with a flat-plane crank is that is can sound like two angry four-cylinder engines next to each other; it's a problem that can't be solved with a simple X-pipe or other crossover tube. To get the sound right, a process that took two years, they started with the unique four-into-two-into-one stainless steel exhaust headers. Equal-length pipes feed into a unique and highly tuned system which winds through mufflers, stuffed in the corners of the car, and exits out the middle through parabolic reflectors which sends the LT6 engine music toward the Z06's cabin. Like other GM offerings the Z06 has an active exhaust which can be anything from crazy loud to stealthy quiet. The result a Ferrari-like scream, but with a somewhat deeper tone. The tuning wizards at Chevrolet set a delay for the direct fuel injectors to encourage a few extra burps and pops on overrun, but only while your foot is moving the throttle. After all, too much of good think is sometimes still too much.
Fun fact: When the pandemic shut GM down all the work stopped, but the computers kept rehashing the exhaust system designs until they determined the center-exit solution. The sound was loved by all but redesigning the rear fascia to house the centrally mounted reverse-megaphone tips cost millions, to us it was worth every penny.
How big of a departure from the "norm" or previous LS and LT engines? Well, aside from what we've already mentioned how about how the starter being mounted in the rear of the LT6's valley beneath the intake while the alternator lives in the same valley but to the front of the mill. The valley is pretty crowded since it also houses the twin high-pressure cam-driven (optimized for 9,000-rpm operation) fuel pumps. Another oddity compared to previous engines are the injectors which side mounted under the exhaust valves. This not only made room for the huge active intake, but it also mixes the fuel better.
The LT6 engine is hand-assembled by master engine builders at the Performance Build Center within the Bowling Green Assembly Plant in Kentucky. Builders use precision tooling and hand fit pieces of the engine to meet Chevrolet's exact specifications. Each engine features a plaque on the intake manifold with the signature of the technician who crafted it from start to finish. A visit to this plant is high on our list of things to do.
Oil is life and to an engine designed for hard road course life a robust oiling system is of upmost importance. In this area, the LT6 engine learned a lot from it's C8.R race-bred cousin. Each piston pair is hermetically sealed off from the other pistons so that the air under the pistons simply back and forth with minimal losses from pumping. The six-bay oil pump, that runs the length of the LT6, scavenges each bay, along with the cylinder heads, and takes 14 hp to operate. The system uses 10 quarts of 5W50 and the rather large cooler is housed in the driver side rear intake. According to Chevrolet track day temps should stay around 250 to 265 degrees.
There are two crank designs available when picking one for your next V8 project: cross- and flat-plane. For the most part cross-plane cranks dominate, especially in American V-8 engines, while flat-plane cranks typically show up in high-end Euro exotics and full-on race cars. Cross-plane cranks give American muscle its distinctive rumble while flat-plane cranks have a tell tail high-rpm whine. But, there's more to these cranks than just their exhaust notes.
Flat-plane cranks, in V-8 and V-12 engines, used to be fairly rare and only seen in uber-expensive super- and hypercars. They're the reason you can always tell a Ferrari is ready to crest the hill at a track day. Just like the name states a flat-plane crank has all its crank pins in a single, flat plane. This is much like an inline 4-cylinder crank, but with more space for more rods.
Flat-plane cranks, no matter what firing order they have, will always alternate from bank to bank. This yields optimum exhaust scavenging and thus doesn't require the more complex header primaries that have to cross over from one bank to the other. Due to their design they don't need huge counterweights, which is why they weigh less and rev up so quickly. The downside is that they suffer from secondary vibrations.
Chevy solved the vibration issue with LT6 engine by minimizing piston speeds, by opting for a large 4.11-inch bore and short 3.15-inch stroke. The result is a 103-mph peak piston speed at redline (for example a the 5.2L in the Shelby Mustang has 114 mph piston speed). Vibration was also helped by the use of titanium piston rods from Austria-based Pankl Racing Systems. Even the aluminum harmonic balancer helps in the battle to solve flat-plane crank vibrations. There are still some vibrations, but nothing detrimental to the car, the LT6, or the Corvette Z06's mission to be baddest Corvette ever built.
anybody else think this car is already outdated and ugly? they copied a ferrari 458/mclaren12c design from over 10 years ago it would seem.
i hope the zr1 is wayyy more aggressive looking...having women test driving it in the video and giggling the entire time doesnt help either. i'd rather see randy pobst beating on it and giving us real data.
impressed with the NA design but wondering how reliability will be. the problem with the gt350 is too shallow of an oil pan and at high revs the oil is tossed up to the top of the motor and starved at the bottom...this car will need 10-12 quarts to prevent that.
Lastly, the clowns wearing masks in the videos was BRUTAL!!!!
i hope the zr1 is wayyy more aggressive looking...having women test driving it in the video and giggling the entire time doesnt help either. i'd rather see randy pobst beating on it and giving us real data.
impressed with the NA design but wondering how reliability will be. the problem with the gt350 is too shallow of an oil pan and at high revs the oil is tossed up to the top of the motor and starved at the bottom...this car will need 10-12 quarts to prevent that.
Lastly, the clowns wearing masks in the videos was BRUTAL!!!!
Impressive for sure. I would happily provide a garage spot for one.
the LT6 and LT2 for that matter have a dry sump oil system, with the LT6 having a much better version of it. that should help with the oiling issues FPC's have.
it seems they did their research on the flat plane crank and went with a ground up design, and at the very least included a cartridge oil filter instead of screw in like ford did with the early GT350's. its an impressive engine. am still not sold off on the rear end but do like that they moved the tail pipes back to the center.
Don't know about that lol. They obviously had a much different set priorities and compromises to deal with. It's not like they couldn't have technically accomplished something like this.
Car awesome , masks fail and especially when back in the dyno cell.
Woah, beats my expectations. 670HP is straight out of Compton badass. I hope it can at least challenge the Huracan STO.
Yes, 58k OTD +tax +doc +adm
I like how they're selling the coupe and convertible at the same time. Kudos to GM for thinking of all the perspective buyers. IMO the vert looks better because of those humps behind the driver/passenger headrest.
Did some more digging, and it seems that its a big overboare. Big bore, short stroke, to keep piston speed down. Ford block doesn't have the bore spacing to pull that off.
FTFYPlaid owns the drag strip and C8 owns the race track.
Mustang owns the Cuck-E.
That's not a very high mark...They run 10.40.
Users who are viewing this thread
