Issue: Feb 2003


GM Prepares to Serve Up Hybrids in Three Distinct Flavors



Production hybrid systems are on their way to the market this year.

by Gary Witzenburg

Skeptics — and there are many — who dismissed GM’s PNGV (Partnership for the Next Generation Vehicle) effort a couple years back as 1) a PR exercise, 2) a waste of money, or 3) both, should take a good look at these soon-to-come production hybrid systems, especially the two-motor “Advanced Hybrid System” set to debut in a Saturn VUE in late 2005.

Beginning as a unique parallel hybrid configuration cobbled together in a stretched EV- 1 concept car — one of five GM advanced technology concepts shown at Detroit’s 1998 North American International Auto Show — this innovative system combined an EV-1 front motor with a small 4-cylinder rear diesel engine supplemented by a smaller second electric motor.

As development progressed from crude concept to polished prototype in the ultratech 80-mpg Precept concept vehicle unveiled two years later, the high efficiency potential of this design became increasingly clear. The negatives were high material and hardware costs, the rear-mounted engine and complex control algorithms needed to smoothly coordinate three separate drive units, a self-shifting manual transaxle, system cooling and accessories.

While the complex and costly Precept vehicle was never intended for production, its mission — besides fulfilling the PNGV industry-government partnership agreement — was to explore whether an 80-mpg family-size car was even feasible and, if so, what it would take to get there. Its long list of technology achievements and innovations was well documented and carefully sorted and studied, and items with production potential were prioritized and pursued.







Now comes this much more practical, affordable and produceable descendant, intended for a wide variety of future FWD cars and SUVs. Teaming two 25-hp (20-kW) electric motors with a 125-hp, 2.0L Ecotec 4- cyl. engine provides a healthy 175 hp to the front wheels. As in the Precept, the transaxle is an automatically-shifted manual 5-speed (MTA) — more efficient than a CVT — and the motors serve no fewer than seven functions: 1) start the engine, 2) propel the vehicle at low speeds (where gas engine efficiency is lowest), 3) propel the vehicle in reverse (no reverse gear needed), 4) charge the 300V NiMH battery when the engine is running, 5) charge the battery during braking (regenerative braking), 6) synchronize the MTA shifts, and 7) drive the AC compressor, even when the engine is off (braking, coasting, low-speed operation). With the system’s advanced control electronics continuously choosing the most efficient power combination — electric, IC engine, both or neither — for every load, speed and acceleration/ deceleration condition, GM claims up to 50 percent potential fuel economy boost.




A much simpler system, available as an option to Chevy Silverado and GMC Sierra fleet customers later this year and to retail customers in 2004, replaces the conventional alternator and starter with an electric motor/generator cleverly packaged (in a patented space-efficient manner) between the 285-hp 5.3L, Vortec V-8 and the automatic transmission. It can improve economy 10 to 12 percent primarily by shutting down the engine whenever the truck is coasting, braking or at a stop. A revised 2007 version with Displacement on Demand (DOD) cylinder deactivation will boost economy 15 to 20 percent in GM trucks and SUVs.

The motor quickly and smoothly restarts the engine on demand and generates electricity during coasting and (regenerative) braking. When the engine is stopped, this electricity drives onboard accessories such as power steering and HVAC. With the engine running, it can provide up to 14,000 watts of continuous 20-amp power though two 110V outlets in the bed and cab. Or it is stored for later use in a 42V PbA battery.









   
   





Available on Chevy’s car-based Equinox SUV in 2006, a third GM hybrid variation is a simple belt alternator starter (BAS) system that will improve economy 12 to 15 percent by stopping the engine during stops and deceleration. As in the truck system, regenerative braking charges a separate storage battery (36V PbA in this case), and accessories are battery powered when the engine is off. This relatively inexpensive and versatile system will be combined with GM’s VTi (CVT) transmission in a variety of 4-cyl. and 6-cyl. applications.



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