by Jim Kerr
Harry J. Pearce
Recently, at the Detroit Auto show, General Motors presented a whole raft of exciting concept cars and trucks. Some of the vehicles were gorgeous; others I found a little overwhelming, but one of the most interesting parts of the presentations was the fact that all the vehicles were running models, and beneath their skins were the latest in automotive technology.
General Motors’ Vice Chairman, Harry J. Pearce showcased one of the technologies, the ParadiGM hybrid-electric vehicle system. It combines the power of a full sized four or six cylinder conventional engine with the torque of two electric motors. Sport Utility vehicles with the new system will hit the marketplace beginning in 2004, but the real exciting news is that this system is suitable for not only cars and light duty trucks, but similar Allison systems could also work in buses, highway tractor units, and other commercial vehicles. The reduction in fuel consumption would be enormous.
The key to the ParadiGM system is a unique computer-shifted six-speed manual transaxle, which for obvious reasons the internal workings were not revealed. Coupled to the transaxle are the conventional gasoline engine and one electric motor on the input side of the gearbox, and another electric motor on the output side. A 3.6-liter V6 version of the hybrid powertrain, which will be offered first, puts out 220 horsepower from the engine, plus another 32 hp from the electric motors. Performance predictions, based on a new SUV, were 0 to 60 mph acceleration times of 7.3 seconds, and a combined fuel economy of 43.7 miles per Imperial gallon. Impressive to say the least!
Pearce described vehicle operation with the hybrid system: “at highway speed, the consumer won’t be able to tell the difference from a conventional vehicle. Pulling away from a light, however, they’ll notice superior acceleration and relative quiet.” The reason for the quiet acceleration is because a ParadiGM powered vehicle will “idle” and accelerate away from a stop on electrical power alone. Electric motors offer excellent torque at start-up. As the vehicle gains speed, the conventional engine starts, adding power at a point where it runs efficiently.
Each of the electric motors has three operating modes. They can power the car during initial acceleration, work as a starter motor for the conventional engine, or they can be used as generators to charge the 42-volt batteries (42 volts is the new standard adopted by the automobile industry). A small lead-acid battery pack will be used initially, but other battery technology is being explored. Keeping the battery pack small limits the range on electric motors alone, but saves weight for better vehicle performance. Range is not limited with the ParadiGM system however, because the conventional engine is used as the primary power source. The batteries can be charged by the engine or by the electric motors when they are used as generators during coasting or braking.
Another innovative feature of the ParadiGM system is the mounting of the air conditioning compressor. It is mounted on and driven by the transaxle. Air conditioning is the second largest user of the car’s energy, only behind the actual moving of the vehicle. Mounting it on the transaxle allows it to be driven by either the conventional engine, the electric motor, or even by the power generated by the vehicle coasting. Driving the compressor by these methods keeps the interior climate comfortable even when the conventional engine is shut off at a stoplight.
Using hybrid powertrains in full size and commercial vehicles offers real fuel economy. An improvement of only 10 miles per gallon (mpg) on a vehicle that gets 25 mpg saves twice as much fuel as a 20 mpg increase in a vehicle that gets 50 mpg. The lower the current fuel economy, the more benefit there is to switching to hybrid type systems. Reducing the total fuel consumption not only lowers operating costs, but also reduces total exhaust emissions produced and extends our energy reserves for future use.
General Motors plans to build more than 7000 SUV hybrids in the first year of production. Who knows; maybe that Semi rolling down the highway will be the next vehicle to take full advantage of GM’s hybrid vehicle technology?