Automotive Engineering - May 2021 - 32

Q&A
Engineering a 'beast' of an electric SUV

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
the development process. We do a
lot more simulation up front. Last
year, we went through extensive
32 May 2021

simulations of everything - on-road, off-road, range, etc. The
off-road simulation we do 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.]

" 800-V DC fast charging
plays into our testing and
development schedule. "

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-ofcharge and ideal temperature?
DC 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.
AUTOMOTIVE ENGINEERING

General Motors calls it a " beast, " a nickname 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 Nm;
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 (254-mm) shorter 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 led
development of the fifth- and sixthgeneration Chevrolet Camaro, including the thundering ZL-1 and
Z-28 variants before being selected
as chief engineer of electric vehicles
Al Oppenheiser,
in 2018. He fielded the following
chief engineer of
questions during a recent media
GM's EV program.
backgrounder on the Hummer SUV's
development.

Automotive Engineering - May 2021

Table of Contents for the Digital Edition of Automotive Engineering - May 2021