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

High Efficiency Generator

High Efficiency Generator

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

Electronic Power Steering

Electronic 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.

2010-chevrolet-equinox-blackI 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

Author: J.S. Smith

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  1. Having read parts 1 and 2, I think the biggest impact will come from automatic engine stop-start systems, since our clueless traffic engineers insist on NOT synchronizing (aka properly timing) stoplights.

    Despite an infusion of technology, from Bosch or someone else, the best thing an automaker can do to meet the (stupid, bas-ackwards) CAFE is to reduce vehicle size and weight. Just look at the evolution of the Honda Accord. The 1976 Accord could probably fit inside the cabin of the 2009 Accord… okay, that’s an exaggeration… but the Honda’s symbolic of the super-size-me growth of all cars.

  2. Man, I hate CAFE!

    I know everyone screams about higher taxes, but I would rather have the price of gasloine a lot higher through taxes than to have CAFE.

    Let everyone make their own decison what to drive, how to drive, where to drive, oreven whether to drive at all when gas costs $5 per gallon.

    Anyway, yeah, stop-start might pay off the biggest short-term. But tire inflation sensors on every car would be an even cheaper way of saving fuel. Lots of people waste fuel by having under-inflated tires. It’s some huge % of the population that has under-inflated tires at any one time, like 45%.

  3. It’s interesting to consider which will become more pressing ten years from now – the price of gasoline or the level of emissions.

    Five years ago the future price of gasoline was the problem. Now it looks like the rising environmental damage from emissions is a much bigger problem.

  4. I’ve never really trusted the EPA milage figures (for obvious reasons). As a result I don’t see start/stop making much of a real world difference, though obviously the manufacturers will use whatever system gives them tgod numbers on the EPA test protocols.

    Every car I have ever owned got almost the same milage in town or on the freeway. Yes freeway is always better but it’s 1-2 mpg better not the 8-1 mpg difference you see on the stickers. My Mustang (with V-6 and stick) gets 23.5 in mixed driving, might get 24 on the open road, and a bit better than 22 if driven exclusivly in town.

    I think Ford/Bosch have the right idea with direct injection and twin turbos though.

  5. my cars do MUCH better on the highway than city, but i never do as well as the avrage fuel economy in the city or the higway.

  6. Well the speed limit here is effectively 82 mph (it’s signed 75, but everyone drives 7 over) that might have something to do with it. (I’m sure the EPA tests at 55)

  7. Freeway mileage is, of course, heavily dependent on the speed at which one drives. My old Lumina–boring but reliable–was a pretty good sized car, and it would get 30 MPG on the freeway so long as I set the cruise right at 70 MPH. It actually go about the same as my old 1997 Cavalier and my current 2001 Focus Wagon.

    My 300, with the 3.5 liter V-6, can also vary. When gas was over $4 per gallon, I set the cruise at just under 70 and drove very conservatively around town–no stomping on the gas pedal, etc. I improved my average MPG from about 19 to 25. Of course, now that gas is cheap again . . .

    Which brings us to CAFE. It may have made sense in the 1970s–I’m not sure the domestic industry would’ve survived the second oil crisis without the downsizing mandated by CAFE, but a gas tax is the way to go. It would make people drive more conservatively, but allow you to keep performance, so long as you’re willing to pay at the pump. Moreover, by having separate standards for light trucks, CAFE created our strange national obsession with the SUV and its cousin the CUV because you could still get big vehicles with big engines. And we seem to like big vehicles–until gas jumps again. The price sensitivity of the car market and the volatility of gas prices makes product planning difficult for automakers, especially our domestic producers with their reliance on SUVs. But we can file that under “ain’t gonna happen.”

  8. As I commented in Part One, until we can make lots of electricity without burning coal or oil, you’re just moving the emissions problem around.

    As “poisson” (fish?) mentioned, emissions need to come down now as opposed to worrying about the price of gasoline. If the solution is electric vehicles, then at least in the short term, we’ll have to generate that clean-emission power for the cars with nuclear power.

  9. I think the new Equinox demonstrates what can be done with direct injection without a turbo.I would like to see it compared to a 1.6 turbo to see what gains are really possible with the more elaborate,expensive solution.

  10. When you look at surveys of teen and 18-22 age drivers, it’s amazing how many want an electric car now, or more importantly, say they don’t want to own a car at all.

    Emissions and fuel consumption would certainly go down if that happens.You gotta wonder how many of these young people will lose their resolve, but if even a portion don’t get a car or make do with an electric commuter car, that will bring consumpion per capita way down.

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