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by Greg Wilson
Alternative powertrains for trucks, including fuel cells, gas-electric hybrids and diesel-electric hybrids, are only a few years away – but only hybrid vehicles with an integrated starter generator have any real potential to match the hauling and towing performance of traditional big block engines.
The next big thing in powertrains will be a marriage of two traditional foes in automotive propulsion: electricity and the internal combustion engine. By 2003, Ford, DaimlerChrysler and GM will be introducing a new-generation of hybrid gasoline-electric pickups and SUV’s that will offer between 10 and 50% better fuel economy, significantly lower emissions, and comparable vehicle performance.
At about the same time, automakers will introduce the first fuel cell and fuel-cell/gasoline hybrid vehicles which will offer little or no tailpipe emissions and even lower fuel consumption. Fuel cell vehicles however, have one big drawback: the fuel! A hydrogen refuelling infrastructure is still in its infancy, and even fuel cell vehicles with on-board methanol reformers (which extract hydrogen gas from methanol) need methanol refueling stations. Gasoline reformers are still in the early stages of development.
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For the near term, the smart money is on gas-electric and diesel-electric hybrid powertrains. Honda and Toyota already have gas-electric hybrid cars (Prius and Insight) on the market and the Big Three automakers are readying gas-electric cars and trucks for the 2004 model year. Ford has pledged to bring a hybrid Escape HEV to market in 2003, and an Explorer hybrid a few years later. GM is working on a hybrid system for the full-size Silverado/Sierra pickups, and unveiled a unique hybrid powertrain called ParadiGM which will be installed in a 2004 model. DaimlerChrysler has a hybrid Durango TTR model and a Ram pickup planned for 2003, and showed a radical concept hybrid SUV called the Powerbox at the recent L.A. Auto Show.
Hybrid powertrains use a conventional internal combustion engine in combination with an electric motor or integrated starter generator, a battery, and an electronic controller. The electric motor and the battery provide additional power to the gasoline engine, thereby improving fuel economy without affecting power output. To further save fuel, the engine automatically stops when the vehicle comes to a stop, and starts again automatically when the accelerator is depressed. The battery is recharged using the energy captured during regenerative braking, relieving the engine of doing all that work, and saving more fuel. A hybrid powertrain is completely self-sufficient – it doesn’t need to be plugged in and charged up overnight.
The Dodge PowerBox concept truck, for example, has a supercharged 2.7 litre V6 engine driving the rear wheels and a Siemens electric motor powering the front wheels. The V6 engine, which is fueled by natural gas, pumps out a healthy 250 horsepower while the electric motor adds another 70 horsepower. This gives it the performance of a big V8 engine and the fuel efficiency of a small, supercharged engine. 0 to 100 km/h is projected to take about seven seconds while fuel economy of about 11 litres per 100 km is a 60 percent increase over a conventional Durango. And as a super ultra low-emission vehicle (SULEV), the PowerBox has a range of more than 560 kilometres, more than most conventional sedans.
However, while some hybrid powertrains have the ability to tow, some do not. So-called “Full hybrids”, which include the Powerbox, Durango TTR, Escape HEV, and GM’s vehicle with the ParadiGM system, are not suitable for towing trailers over long distances. That’s because Full Hybrids depend on their powerful batteries, sometimes running on the battery alone.
“This kind of powertrain will let you pull a boat out of a boat ramp, but if you’re out in Colorado and going up to the Eisenhower tunnel with your Airstream on the back, you won’t have enough energy in the battery to go all the way up the hill,” explains Bruce Zemke, General Motors Staff Development Engineer. “The system will turn off the electric motors to turn off the battery.”
Bob Davis, Vehicle Development Engineer at DaimlerChrysler says the same thing about the Durango TTR. “It will pull a heavy trailer on level ground but isn’t good enough for long grades. We don’t have enough battery power on-board to maintain the boost,” he says.
Though some Full Hybrids have four-wheel-drive, such as the Durango TTR which has an electric motor driving the front wheels and a gas engine driving the rear wheels, they’re not really designed to go off road.
“We can send power to the front wheels but we run into slippage – it’s not the kind of 4X4 you’d want to run over the Rubicon Trail..” says Davis.
In addition, most Full Hybrids will be small to mid-sized cars and trucks with four cylinder or six cylinder engines which don’t have big towing capacities in the first place.
Ford Escape HEV
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“The Escape HEV will feature a hybridized four-cylinder gasoline engine,” explains Ford spokesperson, Jon Harmon. “With the combination of the electrical motor, it will deliver the acceleration performance of the 200 horsepower V6, while retaining the towing power of the I4. So it will still have moderate towing capability.”
Harmon says this will be fairly typical of HEV (hybrid electric vehicle) applications for most of this decade. “The idea is to use the hybrid to get the most fuel economy out of a smaller engine as opposed to adding it to a vehicle with a powerful engine. For RV enthusiasts, I wouldn’t expect an HEV capable of massive towing any time soon,” he says.
Another type of hybrid powertrain however, is capable of heavy-duty towing. So-called “Mild Hybrids” have an integrated starter generator instead of an electric motor. The ISG is sandwiched between the engine and transmission and provides extra boost to the engine under acceleration, helping to save 10 to 15% in fuel costs.
Like a Full Hybrid, the battery is recharged using regenerative braking, and the engine shuts down when the vehicle is not moving to save fuel. Unlike a Full Hybrid, a Mild Hybrid has a much smaller battery than a Full Hybrid and cannot run on battery power alone. In addition, proposed hybrid trucks with this system will have larger displacement six and eight cylinder engines.
“Application of this technology is reasonable for trucks and SUVs that are used for serious towing,” says Ford’s Harmon. Ford will apply this technology to a future Explorer model which will include a six cylinder engine and a new 42 volt electrical system.
“The higher voltage architecture would enable a number of energy-saving technologies, including start-stop and regenerative braking, and conceivably drive-by-wire capability, camless engines, and so forth, without reducing the vehicle’s capacity to tow,” explained Harmon.
General Motors Corporation Vice Chairman Harry Pearce poses with a hybrid powertrain that will be used in full-sized pickup trucks beginning in 2004.
General Motors will add an ISG system to its full-size Silverado/Sierra pickups in 2004. “It will have the same towing capacity and will achieve fuel economy savings because you shut the engine off at idle,” said GM’s Zemke. “I expect 10 to 15% fuel savings in city driving, while highway driving fuel savings will be minimal.”
Still, Zemke points out that a 10% overall fuel savings means more with a bigger engine. “With a vehicle that gets 15 mpg and does 15,000 miles a year.. that’s equivalent to saving 100 gallons of fuel per year.”
Dodge is readying a full-size Ram pickup called the “Contractor’s Special” with a similar ISG system that will save up to 20% in fuel costs.
“The powertrain includes an integrated starter generator between the motor and transmission which gives the engine a power boost of 40 Kw (55 horsepower),” says DaimlerChrysler’s Bob Davis. The Contractor’s Special can also generate 20 Kw of AC electrical power on a continuous basis. Davis thinks this will be of particular use to RV owners who need a separate generator to power accessories. “You can take the space, weight, and maintenance of a separate unit out of the trailer,” says Davis. In addition, the exhaust emissions from the Ram’s engine are considerably cleaner than those of a stand-alone generator, he says.
Both Davis and Zemke expect that ISG-equipped trucks will be more expensive than standard trucks, even though the ISG essentially replaces the conventional starter and alternator.
“You’re putting an electric drivetrain on board in addition to the regular gas engine – so there’s an inherent cost in it,” says Davis. He estimates the cost at about $7500, but pointed out that a ‘tow-behind’ 20 Kw generator would cost more than that.
Zemke would only say that GM’s ISG systems will add to the cost of their vehicles too.
One reason we’re likely to see gas-electric hybrid trucks in the near future is that they’re relatively easy and inexpensive to produce.
“Compared with fuel cell vehicles, hybrids, even in the very short term, present economically viable solutions for the manufacture of low-consumption, low-exhaust vehicles in large production volumes,” said Bernard Robertson, Senior Vice President DaimlerChrysler Corporation. “In fact, from today’s viewpoint, hybrid vehicles have a good chance of constituting an additional mainstay in the further development of the combustion engine, alongside the fuel cell vehicle, in the long term as well.”
The big question for truck makers will be whether consumers are willing to pay a premium to get better fuel economy. A lot may depend on the price of a gallon of gas in 2003.