2023 Chevrolet Corvette Z06 Engine Detailed
It’s surprising how aggressively Chevrolet approached the latest Z06’s all-new engine design. The excitement around the eighth-generation Corvette moving to a mid-engine layout has been bubbling for the last few years. And while that fundamental shift in platform design is worthy of excitement, the standard C8 continues to use a V8 engine with a traditional cross-plane crankshaft.
The 2023 Corvette Z06 features a clean-sheet 5.5-liter V8 engine that utilizes a flat-plane crank; it shares nothing with the standard Corvette’s eight-cylinder. It was developed alongside the race engine in the Corvette C8.R, a car that has already won multiple championships while fully validating the engine’s performance and durability in extreme conditions over the past three years. We’ve driven the new Corvette Z06 and can confirm the engine’s immediate throttle response, broad torque band, stratospheric redline and scintillating exhaust note.
With 670 horsepower and a claimed zero-to-60 time of 2.6 seconds, the Z06 delivers everything an exotic car promises, at least on paper. And with a starting MSRP of $106,995 it does so at a fraction of competitive exotic car pricing. But why does the flat-plane crank design offer these traits for both the C8.R race car and the new Z06? How does this design give the Z06 bragging rights as having the most powerful naturally aspirated production V8 engine ever created? And does it all work as well under real-world conditions as the engine specs suggest?
Let’s start with the inherent advantages offered by a flat-plane crank engine design. There’s a physics rabbit hole related to things like primary and secondary vibrations we could crawl down and likely never emerge from, but we’re going to keep things light and simply state that a flat-plane crank features crank pins arrayed in 180-degree (or opposing) angles from each other. This means all the joints where the connecting rods attach to the crank are aligned in a single — or “flat” plane — versus the 90-degree cross-plane design of a typical V8 engine.
The flat-plane crank layout is usually reserved for race cars or exotic cars because it’s a more sophisticated (read: expensive) design, with cost/benefit tradeoffs that aren’t justifiable in mainstream performance cars. However, advances in modern engineering are making this design more cost-effective (Ford used it for its last Shelby Mustang GT350), and Chevrolet felt this generation of Corvette Z06 deserved a no-compromises approach to engine performance.
And what are the specific upsides of a flat-plane crank compared to the more traditional cross-plane crank utilized in the majority of V8s? The primary benefits are lighter rotating parts and more efficient intake and exhaust charges, both of which allow the Z06’s engine to spin up (rev) quicker and spin to a higher maximum speed (redline). In the Corvette Z06’s case, maximum engine speed is 8,600 rpm (revolutions per minute), or 2,100 rpm higher than the standard C8 Corvette’s 6,500 rpm redline.
After driving the new Z06 we spent some quality time with Dustin Gardner, the assistant chief engineer on the LT6 V8 engine, and he explained some of the key elements contributing to the engine’s performance characteristics.
“A lot of people think the flat-plane crank design allows an engine to rev to higher speeds. But you can spin a cross-plane engine at high engine speeds, too; it’s just that the double firing of the pistons from each cylinder bank crowds the intake and exhaust charge, so there’s no advantage to spinning it up there — and it’s harder to tune. On a flat-plane crank, when your firing order is even from each cylinder bank, it balances the vibration forces while making the intake and exhaust breathing far more efficient at high engine speeds,” said Gardner.
Those two elements, the self-balancing forces on the crank and the naturally synchronized air flowing in and out of the combustion chamber, allowed the engine team to use lighter weight materials and advanced air management tools for maximum performance.
With regard to lightweight materials, the crank in the Z06’s engine weighs 33% less than the crank in the standard C8 Corvette. This combines with titanium connecting rods, low-profile forced pistons, and a lightweight aluminum viscous damper to make everything that spins in the LT6 as light as possible. The result is reduced engine vibration and rapid changes in engine speed, whether applying throttle to accelerate or downshifting when slowing for a corner.
On the air management front, the GM team enhanced the natural breathing advantage of the LT6’s flat-plane crank through an advanced intake manifold design. The manifold uses internal valves to change its volume based on engine speed, dramatically increasing volumetric efficiency. Gardner told us above 3,500 rpm the intake manifold has a better than 100% volumetric efficiency and, combined with the LT6’s specific head design and exhaust tuning, the engine’s overall volumetric efficiency is around 110%.
Normally you can’t get more than 100% volumetric efficiency without forced induction (i.e., a turbo- or supercharger), but that’s what the LT6 is achieving — a forced-induction-like boost without using forced induction. This is why it’s the most powerful naturally aspirated production V8. It’s also why the engine’s throttle response is so immediate and its torque band so wide and flat, pulling hard all the way to the 8,600 rpm redline. And yeah, it helps create the Z06’s killer exhaust note too.
In a track environment these characteristics manifest in relentless forward thrust when the Z06 is coming off a turn. Rapid-fire transmission shifts, initiated by the Z06’s steering-wheel-mounted paddles, allow the engine to pull seamlessly when accelerating, while the lightweight internal components let it spin up, then down, quickly when braking and downshifting before entering a corner. The accompanying exhaust note lends the new Z06 a Ferrari-like demeanor, helping it achieve the exotic car experience the Corvette has long sought and that, after 70 years, feels fully delivered by this new LT6 V8.
Edmunds says
The LT6’s flat-plane crank design has bestowed the new Z06 with a heart and soul on par with Europe’s most exotic supercars.
