2024 Chevrolet Corvette E-Ray In-Depth: All Details About That Hybrid Powertrain

The E-Ray diverges in its operation, even among hybrids. Right from the start, the emphasis was on simplicity. Other hybrid supercars often incorporate electric motors around the transmission, at the wheels, in various locations. Such an approach didn’t align with the vision here. Similarly, propelling all four wheels solely with the internal combustion engine for achieving all-wheel drive seemed less viable. “Implementing mechanical all-wheel drive in a mid-engine car entails a more complex execution. It would undeniably have added more weight,” Holder conveyed.

In contrast, the inclusion of an electric front axle and mid-mounted battery emerged as a far superior choice, for multiple reasons. “The flexibility to utilize [the front drive unit] in a modular fashion, which distinctly sets it apart from most high-performance hybrids, to recapture kinetic energy independently of the internal combustion engine’s operation” provided significant benefits in terms of functionality and manufacturing convenience, he explained. The configuration was evidently too logical not to pursue.

Enabling all these features in a practical manner is a different narrative altogether. The primary focus was on refining the drive unit. It had to be exceptionally compact, lightweight, and potent. After years of meticulous development, the end product materialized as a three-phase radial flux motor paired with two stages of reduction gears, one among which is a planetary set. 160 horsepower is transmitted out of its diminutive and lightweight magnesium enclosure through a petite differential. Even the fasteners are entirely fabricated from aluminum to minimize weight.

“It’s not a result of sheer luck that everything fits together,” Holder revealed. General Motors possesses the internal proficiency to construct fully electric and hybrid vehicles, and that’s precisely what transpired. “We chose not to outsource any part of it.” Everything is developed in-house, except for the battery cells.

The rectangular pouch-type lithium-ion cells are manufactured by LG, yet they deviate from the cells typically found in a traditional electric car. Instead of striking a delicate balance between maximum output current and overall capacity, the cells within the E-Ray predominantly focus on delivering as much immediate power as feasible at any given time, even at the expense of energy density.

The battery itself boasts a capacity of 1.9 kWh, comprising eight 10-cell modules. While these 80 cells can be segregated into the aforementioned modules for practical cooling, assembly, and charging management purposes, they are all interconnected in series. In othIn the world of electricity, the sum of voltages in each cell is aggregated, while the current remains consistent.

To attain a high pack voltage crucial in electric vehicles, especially with a limited number of cells, the arrangement is vital. Horsepower equates to wattage, and wattage results from amps multiplied by volts. High current (amps) leads to high heat, prompting many automakers to favor higher voltage traction systems over higher current alternatives to prevent associated complications. The E-Ray’s pack boasts a nominal 300 volts, slightly below a full EV but ample for a hybrid, and notably high for a total capacity of 1.9 kWh.

The challenge with this configuration is that the total amperage deliverable by the pack equals that of a single cell’s discharge capacity. The mathematics for 160 hp aligns, and within the E-Ray’s pack, this synchronization is impressively achieved

Individually, each cell can output up to 525 amps in a burst but typically maintains around 400 amps during normal driving. “The fluctuations depend on various factors, but we can sustain such peaks for approximately two seconds, contingent on factors like temperatures,” Holder mentioned. This capability is extraordinary. With a full charge, just three cells wired in series could effortlessly jump-start a vehicle. Each pouch, akin to a piece of toast in size, can consistently generate about two horsepower or more momentarily. The E-Ray incorporates 80 such cells. Do the calculations.

Cooling posed a distinct challenge. Most full EVs, despite the absence of grilles in many cases, incorporate heat exchangers to regulate the battery, inverter, and other power electronics’ temperatures. The ultra-powerful and compact battery pack in the E-Ray encounters the same issue, albeit the C8 is already equipped with numerous radiators. To address this concern, inspiration was drawn from full-size trucks, where the amalgamation of an AC condenser and a radiator, dubbed a “conrad,” proved optimal. Holder noted, “It was simply repurposed and designed to fit within the identical condenser space shared by all other Corvettes.”

Observed below, the cooling channels in the heat exchanger widen towards the base. This designates a distinct water-glycol loop associated with cooling nearly all components of the electric drivetrain. The upper segment featuring narrower channels corresponds to the AC condenser.

The integration of advanced software controls elevates all this technology, showcasing GM’s expertise in introducing innovative features to this car. Notably, during track usage, the E-Ray’s battery might rapidly exhaust due to consistent high-power demands. To counter this, the vehicle boasts a straightforward yet effective Charge+ mode.

It kicks off by prioritizing regenerative braking whenever feasible. Holder humorously remarked, “We refer to it as free beer. Whenever it’s available, seize the opportunity.” This process aligns well with the E-Ray, given its battery cells’ high power absorption capacity. While the cells can discharge 525 amps in a burst, they also accommodate short-term charging of 400 amps. Consequently, the vehicle can absorb up to 120 kW during braking, a near-equivalent to many high-speed EV chargers’ output. In some scenarios, particularly on non-asphalt surfaces, this level of regeneration could potentially lock the front wheels, though Holder emphasized the presence of advanced traction estimation systems to avert such issues.

Charge+ also moderates the battery’s discharge rate by effectively controlling the available current. Coupled with increased energy from regeneration, extended operational periods become feasible. This ismost effectively demonstrated in the graph below. You can also observe how the vehicle maintains a reserve of power to ensure constant all-wheel-drive capability.

Furthermore, each new Corvette is equipped with active fuel management, also referred to as cylinder deactivation. This feature allows the car to operate on either four, six, or eight cylinders based on the load, resulting in fuel savings. With the assistance of the electric motor, the duration of operating with fewer than eight cylinders firing can be significantly prolonged. “We refer to it as AFM extension,” Holder expressed. “By leveraging the electric motor, we can prolong the AFM duration… Ascending terrains serve as a prime example of observing this in action.” This leads to the E-Ray, with its 345-mm rear tires and drag-inducing downforce elements, achieving the same combined fuel efficiency as a standard Stingray (19 mpg), despite boasting 655 hp compared to the base model’s 495.

Flexibility was the central theme here. The hybrid system in the E-Ray is exceptionally compact and compartmentalized. Critics of hybrid vehicles often argue that they are intricate and more challenging to fix, but from the outset, the E-Ray was developed to address that apprehension. All the batteries and power electronics are contained within a single unit that can be easily removed from the underside of the car. “[It’s] all within one module, they are housed in a composite-encased enclosure,” highlighted Holder. “Simply disconnect the cooling lines, phase cables, and some electrical connections, and detach it from the bottom.”

GM appears to have mastered this hybrid supercar concept. It raises the question of why other car manufacturers insist on incorporating more motors, batteries, and complexity. Consider vehicles like the BMW i8 or Acura NSX. Are those additional features truly essential? In comparison, this model just operates seamlessly. The total power figure is simply the sum of the outputs of the two systems. It accelerates phenomenally and offers an exhilarating driving experience. Moreover, the incremental weight—the E-Ray weighs only 260 pounds more than a comparable Z06—is quite acceptable. In a scenario where the pure ICE-powered BMW M2 surprisingly weighs more than this, it is evident that hybrid cars do not necessarily need to be heavy, and this particular one isn’t.

The only aspect that feels lacking to me in this entire scenario is greater control. I briefly touched on this in my evaluation; however, when equipped with two distinct drivetrains like this, the magic lies not just in having them but in managing how they operate and interact harmoniously. If I desired to extend the all-electric range as much as possible, I should be afforded the option to regulate the peaks in terms of battery current discharge on my own. I understand that this is not an electric go-kart, but I possess adequate knowledge of inverter functionality to recognize that such control is entirely feasible.

Electric drivetrains, particularly when coupled with an exceptional combustion engine, exude a distinct appeal. Terms like “flux” and “phase” are omnipresent—it’s essential to cultivate enthusiasm for these concepts. If a driver lacks the ability to shift gears manually, allowing manipulation of certain current levels within safe parameters could serve as a worthy alternative. Install a phase cable temperature gauge on the dashboard so that I can monitor how the current impacts the windings in the motor. Granting me more authority over the charge and discharge curve is crucial. Furthermore, having the ability to apply regenerative braking manually would be a welcomed addition. These enhancements fall well within the capabilities of the inverters I utilize, each priced at $100. Surely, GM can materialize such features.

Setting aside minor grievances, the E-Ray stands out as arguably the most impressive Corvette ever engineered from a technological standpoint. Reducing the car merely to its 2.5-second zero-to-60-mph acceleration time (a new record for any factory Corvette) would undermine the comprehensive nature of the project, hence my deliberate omission of this statistic. The vehicle has undergone nearly a decade of development, and the results are evident. It serves as evidence that performance hybrids need not be unnecessarily convoluted. My fervent wish is to witness numerous similar creations in the future, not limited to those by GM alone, but spanning across a diverse array of automakers. This configuration stands as a resounding success.

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