The New Corvette ZR1 Pushes Engineering to Extremes

"It does feel like, in the internal-combustion-engine age, we are getting very close to the limits of its performance. And if we go out on this one, you know, what a mic drop. It’s just incredible.”

“We never just do an engine program,” says Tadge Juechter, Corvette’s recently retired executive chief engineer. “It’s always a fully developed car, and this car is no exception.”

This story originally appeared in Volume 25 of Road & Track.

A fair point, but since 1990, the focal point of the Corvette ZR-1 and its nonhyphenated successors has been the engine. The LT7 in the new 2025 model is so spectacular that reciting the specs is delicious: 1064 hp and 828 lb-ft of torque. It spins to 8000 rpm. It propels the ZR1 through the quarter-mile in under 10 seconds and to a top speed beyond 215 mph, according to Chevrolet. The LT7’s insane abilities dictated every other change related to developing the ZR1. The complete package was built around the engine. Roughly 10 years ago, when work began on the C8 generation, the front-engine Corvette was hitting an evolutionary dead end. Adding power required a supercharger on top of the engine, the muscular hood bulge hampering the view forward. In the back, wheelspin was barely checked by the latest electronic aids, even with sticky rubber.

Excluding diesels, this is GM’s fourth factory turbocharged V-8 dating to Oldsmobile’s 1962 Turbo-Rocket 215, which didn’t perform to expectations. The turbocharged 301 in the 1980 Pontiac Trans Am was fragile, laggy, and slow, while Cadillac’s short-lived Blackwing twin-turbo 4.2-liter V-8, introduced in the 2019 CT6-V, never had a chance to flourish. The LT7 is the first turbo motor installed in a factory Corvette. And no, the Callaway Twin Turbo of the Eighties doesn’t count. Fourth time’s the charm.

Moving the engine rearward raised the Corvette’s performance ceiling. And the ZR1 was always part of the plan, arguably a key reason for the switch. “When we get this massive power output out of the engine, the mid-engine architecture enabled putting that power down like never before,” says Corvette chief engineer Josh Holder. That also made room for the engine to grow outward, free from the packaging constraints dictated by front crash-structure and steering components. Knowing this, the Corvette team planned a chassis that could fit side-mounted turbos.

Why not stick with the tried-and-true supercharger? “You start playing in the 1000-horsepower realm, you’re going to have to run a 200-horsepower supercharger to make that kind of power,” says Dustin Gardner, small-block engine assistant chief engineer. “So the inherent efficiencies of turbocharging become a big deal.”

Then there’s the perk of keeping those new components low, helping lower the center of gravity and leaving room for the folding convertible top. As with the C7-generation ZR1, the new ZR1 comes in both coupe and droptop form.

The full open-air experience means skipping the return of the split rear window, which offers a glimpse of the Edge Blue finish on the engine intake. It’s a purely cosmetic feature but awfully pretty. The rest of the engine’s changes are assuredly not cosmetic. Here too it was planned early in the C8’s gestation that the Z06 and ZR1, internally known as the Gemini twins, would share a basic engine architecture. The two all-aluminum V-8s were designed in parallel so that neither was constrained by the other. “Everything that needed to be bespoke for the turbo engine was bespoke for the turbo engine,” Juechter says.

So the LT7 in the ZR1 shares a block casting with the Z06’s LT6. Both use a rev-happy flat-plane crankshaft, although the LT7 has different machining to allow clearance for the shorter, stronger rods and longer piston skirts. Stroke remains the same at 80.0 mm, keeping both engines at 5.5 liters of displacement, but the lower, dished pistons in the LT7 and a revised combustion chamber drop compression from 12.5:1 to a more boost-friendly 9.8:1. Unique heads on the LT7 have room for both port and direct injection, with all 16 injectors required to feed the engine at max load. The dry-sump oil system also has a seventh scavenge pump dedicated to both turbos.

Peak boost from the BorgWarner turbochargers is about 20 psi, 6 psi more than the supercharger in the C7 ZR1’s LT5. On the compressor side, the vanes are made of MAR, a high-nickel alloy that tolerates heat better than the more common Inconel alloys—handy when exhaust temperatures can reach 1900 degrees Fahrenheit—and a magnetic sensor tracks exactly how fast things spin. With turbos, “there’s some point that they go ballistic and come apart,” Gardner says. “If you know the speed of it, you can run much closer to that redline.”

That, along with electronic wastegates, allows the engine management to actively modulate the boost and reduce turbo lag. Jump off the throttle and brake hard, and the system assumes you’re about to enter a corner. “It’ll go into closed-loop boost control,” Gardner explains, “even though you’re not fully fueling and your throttles are closed. We’ll close the wastegate, we’ll control to a boost pressure ahead of the throttle. So when you come out of that braking zone, that corner, and you roll back into it, the turbo’s at speed, you have boost ready to go.”

The cool air required to feed the LT7, with its trick turbos and high heat output, directly affects the ZR1’s bodywork. The entire front end is dedicated to heat exchangers, double thick in the middle and on the sides. The design sacrifices the front trunk but creates better aerodynamics, according to Juechter. “We take air in through the front, and it exits the heat exchangers and goes up over the top of the car and helps power the rear wing so you don’t have air going underneath the car creating lift,” he says.

Moving backward, the big openings behind the doors feed a transmission cooler on the passenger’s side and another engine radiator on the driver’s side. Just aft of those familiar vertical openings are new smaller horizontal ducts for rear brake cooling. It’s another place where the Corvette team planned ahead. “We’ve had this sweeping gesture on the side of the car for Z06,” Juechter says. “It’s there because we knew we were going to be taking air in at this area, later, on this car.” The intakes on top of the rear fenders route to the engine intake, determined by digital modeling as an ideal location to pull in cool air.

The LT7 routes power through a Tremec eight-speed dual-clutch automatic transmission. Just visible when peering around the ZR1’s quad exhaust tips, it looks identical to any other C8 transmission from the outside. Knowing the ZR1 was coming, engineers designed the gearbox housing to accommodate the wider gears necessary to handle all the extra torque. Stronger gearshafts also help ensure that the 800 lb-ft available from 3000 rpm won’t cause any trouble.

“All of this stuff compounds,” says Holder, explaining how the power also requires upgraded brakes, which are roughly the same size as the Z06’s optional discs. “They’re carbon-ceramic rotors still, but the fibers in the rotors are longer and more continuous, and therefore, the composite material has more thermal conductivity.”

Wheels and tires on the ZR1 match the Z06 in size: 275/30R-20 in the front and 345/25R-21 in the rear. Michelin Pilot Sport 4Ss are standard, while Pilot Sport Cup 2 R tires come on the ZTK package, which also includes stiffer springs, and the Aero package, with its towering rear wing. The rest of the suspension is familiar Corvette, with standard Magnetic Selective Ride Control adjustable shocks. A new 10-spoke carbon-fiber wheel is optional on any configuration, and Chevy says the 40-pound total weight savings effectively knocks 1.5 seconds off the lap time on the 2.9-mile Milford Road Course at GM’s proving grounds.

Inevitably, in the incubation of any car, issues arise. Some are solved with virtual analysis; others only come to light when the car takes physical form. It’s also why Chevy took the wraps off the ZR1 now, more than half a year ahead of the mid-2025 start of production. For the ZR1, it seems that most of the problems resulted from overshooting the performance targets. The tires were a known quantity at the start. “We developed it with the Z06, so we know its grip capabilities,” says Holder. “But now we get into how much load the carcass can handle and what it does to performance over time.” This necessitated an upgrade. “We exceeded those goals, and then we had to adjust the construction of the tire to match the actual outstanding performance.”

Increased power and higher speeds also meant modifications to the Aero package. Specifically, more downforce was needed from the big rear wing. As Holder tells it, “That load is higher than we planned originally. So we’ve had to revise the support structure underneath that wing to now handle those loads. What once was going to be common with the Z06 now has to be different because of what the ZR1 does.”

The key to working through the development process is “we have a very close team,” Holder says. “And it’s a great thing for us because we’re always working together.” One example is buy-off rides, where the Corvette team drives the prototypes in a group or against benchmark vehicles like the Ferrari SF90 (yes, GM bought one for comparison) to see how everything comes together. And an improvement in one part of the car might upset the balance elsewhere. “Even though the sub-system might be awesome, the integration of it could be very terrible. So we start with a goal, and then we check in almost constantly along the way.”

For Holder and his colleagues, making the ZR1 fast is one thing. Making it fast while retaining the daily-driving capabilities of the base Stingray is another. “It’s pretty easy to make an extreme vehicle that will last a couple of laps. It’s a lot harder to make one that will be durable for the intended life of something like a Corvette.”

Then there’s the almost intangibility of how the car feels. Undoubtedly, the ZR1 will post impressive lap times, but getting there should be half the fun. The sports-car world is rife with examples of cars that look good on paper but fail to tingle the spine. Even the Corvette has some in its family tree. “We’ve got examples of cars we made where, yeah, they’re super capable, but they’re maybe not as fun to drive,” Holder says.

Avoiding the fast-but-boring trap is tricky when the ZR1’s base configuration has softer spring rates than the Z06. “It actually feels more compliant, more daily-driver capable, and less in your face than a Z06,” Juechter says. That version needs to be engaging to drive, but so does the track-focused ZTK, with the stiffer suspension, aero bits, and Cup tires. “So we’re spanning a bigger market bandwidth on ZR1 than we are on Z06.”

What keeps the ZR1 approachable for all yet still rewarding for the expert are drive modes, according to Holder. “It doesn’t just change the display or an icon on your instrument panel,” he says. “It changes a lot. And one of the big things it does is change the way we handle chassis controls like Performance Traction Management.” PTM, as a reminder, is GM’s multistep stability-control program that progressively lowers electronic intervention. “You can go from conservative to aggressive and decide how the car reacts in a safer way than just jumping in and finding the limit by crossing it. That also helps us make the car more playful for those who want it that way or more buttoned down for those who don’t. When you’re talking about a car with power like the ZR1, it’s even more important to be able to give customers some choice in their driving experience.”

Automotive development relies on the scientific method, and test drives are peer review, a necessary step in validating hypotheses. The ZR1, though, stands on the previous results of the Z06, a sublime performance machine on its own. If the ZR1 can replicate that brilliance at higher performance levels, how will Chevy ever top it?

Holder says they’re nearing the limit of the C8 chassis with the ZR1. “We’re almost there already, with a mid-engine architecture and the output of the engine.” And while nobody on the Corvette team will say what’s in the pipeline, one wonders whether more power isn’t the solution. At some point, faster isn’t better.

“I think you start to see some of the diminishing returns,” Holder says. “But you know, 10 years from now, I’d probably say the same thing when we jump across that next level. It does feel like, in the internal-combustion-engine age, we are getting very close to the limits of its performance. And if we go out on this one, you know, what a mic drop. It’s just incredible.”

2025 Chevrolet Corvette ZR1

Price:$190,000 (est)Engine:Twin turbo 5.5-liter V-8Output:1064 hp @ 7000 rpm 828 lb @ 6000 rpm

Transmission:8-speed automaticCurb Weight: 3925 lb

0–60 mph: 2.6 sec