Engineering a ‘Beast’ of an Electric SUV
More use of simulation and a mixed-materials body structure are among the GMC Hummer SUV’s highlights, noted GM’s EV engineering chief Al Oppenheiser.
General Motors calls it a “beast,” a nickname that the 2022 GMC Hummer SUV earns on its numbers alone. Like the electric Hummer pickup, the SUV packs a propulsion system capable of generating 830-hp (619 kW) and 11,500 lb-ft (15,592 N-m; both are GM estimates). It includes a “Watts to Freedom” feature that functions like an electric afterburner to boost acceleration.
Equally impressive are the Hummer SUV’s basic geometries. Its 126.7-in. (3218-mm) wheelbase is nine inches (229-mm) shorter than the pickup’s, yet the SUV’s 35.4-ft (10.8-m) turning circle is tighter than that of the Ford Mustang Mach-E, which has a 10-in-shorter (254-mm) wheelbase. And for customers who might point the beast off road, its 34.4-degree breakover and 49-degree departure angles are more aggressive than those of the 2021 Jeep Wrangler.
Thirteen inches of suspension travel; an underbody camera; an available “crab walk” 4-wheel steering system that enables diagonal vehicle movement; a 120-V, 3-kW onboard generator, and capability for 800-V, 300-kW DC fast charging are some of the Hummer EV features created by Al Oppenheiser’s team. A 36-year GM engineering veteran and unabashed performance enthusiast, Oppenheiser (right) led development of the fifth- and sixth-generation Chevrolet Camaro including the thundering ZL-1 and Z-28 variants before being selected as chief engineer of electric vehicles in 2018. He fielded the following questions during a recent media backgrounder on the Hummer SUV’s development.
Does GM have a new vehicle test regimen for its Hummer EV portfolio, compared with the IC-engine trucks?
Yes. All vehicles go through stringent validation processes for durability, propulsion, drive units, ride and handling, temperature, angle grades, etc. We’ve changed the game quite a bit here in terms of how we test these vehicles. One of the biggest innovations is more virtual tools to help speed up the development process. We do a lot more simulation up front. Last year we went through extensive simulations of everything – on-road, off-road, range, etc. The off-road simulation we do, in a simulator, is impressive. Then transitioning into the vehicles, it’s uncanny how similar the real-world driving is to that of the simulator. The vehicle certainly invites speed and enjoyment when you’re driving it. And because of the obvious EV advantage over an IC engine vehicle, we’re factoring in 800-V DC fast charging, which plays into our [testing and development] schedule.
[GM’s all-in commitment to EVs has led the company to expand its driver-in-the-loop simulation capabilities, adding new systems featuring faster image generation, higher resolution, and significantly quicker response to steering and pedal-force inputs, according to sources at the Milford Proving Ground.]
Talk about the Hummer SUV’s body construction and materials.
This isn’t a traditional structure by any means. We have a mixed-materials strategy. The MultiPro rear gate is aluminum; we have a long list of different steel alloys in this vehicle. As a key part of both the Hummer EV pickup and SUV, we took an advanced technology within GM – a sandwich-type construction. Two rectangular steel plates protect the battery and provide the vehicle’s torsional rigidity. The battery and that structure are integrated, making the vehicle’s off-road capability superior to a traditional body-on-frame or even an integrated [unibody] structure.
Can the battery pack be fully immersed in water?
Water fording [for the Hummer SUV) is 32 inches. While it’s a sealed battery pack, it’s never advisable to leave any vehicle stationary in standing water.
What is the ideal DC fast charging curve, given the optimal state-of-charge and ideal temperature?
DC fast charging is faster, the lower the SoC [state of charge] level. It’s a physics equation. With the 20-module battery pack we’re able to get 20 miles [of range] in 12 minutes. This helps take the charging anxiety out of an EV customer’s mind.