The Drive to 35.5 Miles Per Gallon, Part Two
In Part One, we covered technologies that can be applied to internal combustion engines to improve fuel efficiency. In Part Two, we cover changes that can be made to a vehicle’s electrical system to improve fuel efficiency in the drive to reach the mandated 35.5 miles per gallon bogey.
By J. Smith
It doesn’t take an engineer to realize that new powertrain technologies can increase fuel economy without eviscerating performance. Indeed, coupling an EcoBoost with a six-speed tranny and adding in a little aerodynamics should yield both better MPG and elapsed time. But electrical systems can also help. As noted in Part One, Bosch does not specialize in hybrids or battery systems – both of which will be key technologies in the future. While the omission from Bosch’s presentations was obvious, so was the reason for the omission.
Start-stop and high-efficiency alternators
First of all, start-stop systems are an easy way of getting an extra MPG or two in the city. Bosch has a system that is currently used by the Porsche Panamera. Unfortunately, a Panamera was not available for test, but simply shutting down the engine at stops will result in better fuel economy in stop-and-go city driving in any vehicle. Bosch expects these systems to be in 80% of new European cars and 40% of new North American cars by 2015.
Start-stop has the advantage of being conceptually simple. In terms of technology, it is also easy to implement in existing platforms. The key is to make the starting and stopping as seamless as possible so that consumers don’t notice it. In addition, stronger batteries are needed to cope with a lifetime of constant starting and stopping in the course of ordinary city driving.
Other than starting, a car’s electric system uses electricity generated from an alternator, which runs off an engine belt. Increasing the efficiency of alternators means that they can generate an equal amount of electricity while using less engine power. And because some sort of fossil fuel power engines, better alternator efficiency will result in increased fuel economy.
Electric power steering
Most automobile power steering systems use hydraulic pumps that are powered by the engine. The hydraulic pump is always engaged, whether or not the driver is actually steering, and they use more engine power when the wheels turn. Electric systems, on the other hand, are powered by small electric motors that only engage when the car is steered. Even when activated, they use a fraction of the energy of a hydraulic system. In addition, electric systems are less complicated—no pump, no fluid, no hoses and no reservoir—just small electric motors built into the rack-and-pinion system.
Bosch says that electric power steering systems use 90% less power than conventional hydraulic systems. According to the engineers, electric systems save 4 kilowatts over hydraulic systems during peak steering use. Even at idle, hydraulic systems use about 500 watts of power. Bosch’s electric system only uses 0.5 watts at idle. No, that is not a misprint.
Bosch made several test vehicles and a slalom course available to test its electric power steering system. The first car I drove was a 2010 Audi TT with the Bosch system, which it developed with ZF Friedrichshafen AG (guess which country from which ZF hails?). It had a 2.0-liter turbo-charged I-4. I have to say, the cockpit of this car is absolutely beautiful. Low slung, covered in sumptuous black leather, it is very sporting. Audi claims the car to be a 2+2. At first, I didn’t notice the rear seats; I figured the space was purely for storage. But my co-pilot, an engineer, pointed out that they are indeed seats—“insurance seats.” To fit anything other than an infant seat, however, would likely involve painful lower limb amputation. Consider it a two-person only car. At any rate, it zipped through the slalom nicely. Although it didn’t have ideal feedback, it had nice, tight steering.
Next on the roster was a Euro-spec Audi A4 with the Audi Dynamic System, which has tighter steering at low speed and looser steering at high speeds. Thus, you can parry and thrust through the urban jungle—or slalom courses—with amazing agility yet not run off the freeway if your arm twitches while hitting the century. This one featured a 3.0-liter diesel V-6 and a manual tranny. So plentiful was the torque that I left it in third for most of the slalom and the brief drive back to the parking area, forgetting it was even a stick and stalling it out when I stopped. The A4 was truly a pleasure to sling through the slalom, turning on a dime, feeling like an extension of my arms as I zinged it through corners and around orange cones. Excellent steering feedback. Of all the cars I took through the slalom, this one, with its high-tech hydraulic system, inspired the most confidence.
I then drove a 2010 Chevy Equinox. Yes, I drove this ill-handling beast through a slalom course. Why? Because it was there. It had the 2.4-liter with a six-speed auto and boasted 22-MPG city and 32-MPG highway, which is quite good for this class of vehicle. It also features the Bosch-ZF electric power steering system. As an aside, it boasted a very nice interior—GM has made gigantic strides in this area compared with my last GM whips, 1997 Cavalier, 2000 Lumina and a 2003 Malibu. Needless to say, after the TT and the A4, taking the Equinox through the slalom was a little like piloting the Titanic through an ice floe. The steering was tuned for suburban tastes, which meant high-effort. The wheel had to be cranked and cranked to weave through the cones, whereas the A4 simply needed a firm tug here and there. And the curves—let’s just say it ain’t a sports car. By SUV standards, this may handle well, but not surprisingly, it fared poorly in the company of the Germans.
The final course of the day was a BMW 328i, a US-spec car featuring Euro-spec steering. What made this interesting was that a ZF engineer in the passenger seat had a laptop plugged into the steering system and could vary the steering effort with a click. The standard Euro-spec steering was good—much like the TT’s. He then made it 20% heavier, thus opening a gate into steering heaven. Then, for the final run, he made it 25% lighter; this made it a little too light for my taste, but it was more Sam Adams Light than Bud Light. Even more interesting was that although the steering effort changed, the ratio remained the same. Light or heavy, it responded just as well, which, being a 3-series meant it responded quite well. The engineer informed me that although he could vary the steering with a click, it would not be possible for an owner to simply push a button to change steering effort, but that it was at least theoretically possible to program a car with that capability.
In all, the electric power steering has promise. It does, however, need work because the best steering feel, at least among the cars I drove, still came from the hydraulic system. I hope, however, that in time electric steering can equal hydraulic steering. A final benefit of electric power steering is that if the car loses power, the battery can still power the steering system, but a hydraulic system irrevocably loses power. Trust me, I know.
I had a dandy time sampling the technology at the track. Funny how that turned out to be far more interesting than hearing the tech people speak. Some of the systems shown have yet to reach their full potential, particularly the electric systems. Others can offer better fuel economy right now, mainly engine systems. But all of them will come with a price. The question is whether North American consumers will go for the high tech and retain performance, or will prefer less expensive, but performance-sapping ways to get to 35.5. It could be both, resulting in an even more price-segregated new car market, with the haves getting to eat their cake and the rest of us making do with cold cereal. But even cold cereal can taste pretty good with a little sugar on it.
COPYRIGHT Autosavant – All Rights Reserved