There aren’t enough superlatives in the world to accurately capture our feelings about the new 2023 Chevrolet C8 Corvette Z06 and its high-revving dual overhead cam 5.5L LT6 V8. It’s an absolute marvel of modern internal combustion engine know-how – the most powerful naturally aspirated V8 ever fitted to a production car, with a monumental 670 peak horsepower and an 8,400-rpm redline.
To achieve this in the new C8 Corvette Z06, GM borrowed a trick Ferrari has been employing for decades, and one that Ford lifted for the high-revving 5.2L “VooDoo” V8 that powered the most recent Ford Shelby GT350 Mustang – another motor with output in excess of 100 horsepower per liter. That trick is the flat-plane crankshaft. Without getting too bogged down in the details, a flat-plane-crank V8 utilizes a completely different firing order from a cross-plane-crank engine – one that enjoys more even, steady intake and exhaust pulses. More even pulses means freer breathing, and since an engine’s power and redline are often restricted by how well it can breath at high rpms, that superior breathability – bolstered by its four-valve-per-cylinder design – counts for a lot.
You probably already knew all this. But what you might not have known is the other nifty trick that GM’s engineers deployed to squeeze 670 jaw-dropping horsepower and a considerable 460 lb-ft of torque out of a 5.5-liter space: an active intake system that leverages the phenomenon of Helmholtz resonance to yield big power with a nice, flat torque curve.
Is That Your LT6 Intake Whistling, Or Are You Just Happy To See Me?
SAE International published an article exploring the clever active intake system of the LT6 engine exclusively found in the C8 Corvette Z06, and it all boils down to this: sized and shaped correctly, an engine induction system can maintain positive pressure relative to atmosphere by leveraging our centuries-old understanding of resonant frequencies. That understanding of resonance originated from German physicist Hermann von Helmholtz in the 1800s, who discovered that certain frequencies of vibration corresponded to certain resonance chamber sizes.
In other words, if you tune the length and cross-sectional area of an intake just right for a given engine, the vibrations through the incoming air actually help maintain pressures higher than atmospheric – even naturally aspirated, without the use of forced induction. Easy-peasy, right?
Not so fast. Remember: engines operate at a range of different rotating speeds. Different rotating speeds mean different piston velocities, and therefore, different resonant frequencies. The best you can hope to achieve with a static intake design is one tuned to provide maximum intake airflow at a single operating RPM.
That’s where the “active” part of the Chevrolet Corvette Z06’s active intake system comes in. The plenum contains three “communicator” valves, controlled by electric servo motors that are spoon-fed instructions by the ECU, that connect the two mirrored halves of the plenum together. The first two open together, beginning at about 2,000 rpm at wide-open throttle, while the third remains closed until 5,800 rpm. The purpose of these valves: to dynamically alter the volume of the chamber in order to take advantage of Helmholtz resonance and cram more air into the engine.
Take out the valves and you might have an LT6 intake that can support the same 670 peak horsepower, but the torque curve goes to hell and Johnny Customer, who didn’t realize that a 5.5L V8 could even rev past 6,000 without exploding, goes and complains about the lack of “pick-up.” But with the valves, the 2023 Chevrolet Corvette Z06 is able to have its proverbial cake and eat it, too, achieving the highest power rating of any production V8 in history while delivering ample torque to keep Johnny satisfied.
The net result of all GM’s efforts is a volumetric efficiency that exceeds 110%, according to the SAE, and plenty of bragging rights. It’s yet another way that the 2023 Chevrolet Corvette Z06 continues to wow us with its gobsmacking tech.