In the very early 1990s, GM was in the midst of translating its one-off Impact electric vehicle prototype into a car that could be readily manufactured. At the time it was toying with a variety of power schemes and motor combinations to determine the best for its new electric drive system. We experienced first-hand GM’s focus on developing a practical electric powerplant for its soon-to-come EV1 electric car at the GM Desert Proving Grounds in Phoenix, Arizona. Here, Green Car Journal editors drove several test cars for the EV program including an electrically-powered Chevrolet Lumina APV minivan and an electric Geo Storm.
What was unusual about the vehicles was the application of individual electric propulsion at each front wheel using a pair of motors. Clearly, there was work to be done. Synchronization imbalances in these test mules caused steering to be uneven, but the engineering direction was there. The EV1 eventually made its way to limited production but with a single electric drive motor. This appeared to relegate GM’s two motor effort to an historical footnote in its drive toward electrification.
As it turned out, this didn’t end GM’s exploration into motors power individual wheels. In 2004, the automaker created an innovative motor-in-wheel drive system that was quite unlike its earlier efforts. It demonstrated this technology in a Chevrolet S-10 hybrid electric pickup equipped with in-wheel motors at each rear wheel. This supplemented front-wheel drive power provided by the pickup’s 120 horsepower, 2.2-liter internal combustion engine.
Developed by GM's Advanced Technology Center and made in Italy, the motors generated about 34 hp (25 kilowatts) of power each and added 80 pounds total to the rear wheels. The automaker turned to Southern California-based Quantum Technologies, a vehicle integrator, to build the concept truck. Quantum modified the vehicle's coolant, power, and electrical systems, and developed its special electronic controller and related software.
Green Car Journal editors had the opportunity to test drive this motor-in-wheel equipped S-10 in Los Angeles back in the day. The result was affirmation of GM’s strategy. The S-10 exhibited significantly more power than a stock variant and acceleration was definitely impressive. According to GM engineers, these hub motors added about 60% greater torque at launch with that torque available instantly, a power scheme that enabled a four-cylinder engine to perform like a six-cylinder.
At the time of our test drive, this in-wheel motor concept was not viewed by GM as an electric vehicle drive system. It was a hybrid strategy that could potentially be added to any number of vehicle models to deliver higher performance and significant fuel economy improvements. The technology didn’t materialize as a popular hybrid application as the field evolved. Still, we see that in-wheel motors have very real potential today in the battery electric vehicle world as they are championed by some automakers and suppliers like Protean Electric and Elaphe Propulsion Technologies.
