Navigant Research Blog

Schaeffler Shows One Path to Better Fuel Economy

— January 30, 2015

January in Detroit heralds the annual North American International Auto Show (NAIAS), where many manufacturers launch new models and technology.  It’s less well known as a supplier event, but many of the Tier One companies hold press and industry events to showcase their developments, primarily during the media and industry days that are held before the show opens to the general public.

This year, German supplier Schaeffler chose to highlight its project on fuel economy, with a view to meeting the upcoming more stringent American CAFE requirements.  As well as developing specific components and products, the company has incorporated them into an existing vehicle to demonstrate the integration potential.  Phase 1 of the implementation shows one way to meet the 2020 CAFE target on an existing vehicle by making a series of small, low-cost changes; Phase 2 will add additional features to meet the 2025 fuel economy goal.

Hunker Down

The target vehicle chosen was a model year 2013 Ford Escape AWD (all-wheel drive), which features a 2.0-liter engine and Ford’s 6-speed automatic transmission.  For phase 1, Schaeffler engineers implemented an AWD disconnect feature to eliminate additional friction when only two-wheel drive is necessary, a new torque converter damper to allow a lower lockup speed, and an automatic engine stop-start system.  A new thermal management module enabled faster engine warming from cold.  Other detail changes included coated tappets, new balance shaft bearings, and low rolling-resistance tires.

To reach the 2025 target fuel economy, phase 2 houses two main features: ride height adjustment and disconnecting vehicle accessory drives from the engine.  Automatically reducing the ride height as speed increases is a straightforward way to reduce aerodynamic drag, a topic that I discussed in a previous blog.  The idea of disconnecting accessory drives has been around for some time, and is key to extending the value of stop-start systems, but replacing a traditional crankshaft belt drive with individual electric motors is a very expensive solution.

Clutch Move

Schaeffler solves this dilemma by setting up a separate 48V motor generator to power the accessories when the engine is switched off.  The system is controlled by a pair of clutches that can connect the electric motor to either the engine or the transmission.  Using a 48V subsystem allows more powerful regenerative braking than a 12V system, and therefore greater energy recovery, and the motor can also be used to supplement the drive.

Navigant Research has recently released a detailed report on this topic: Automotive Fuel Efficiency Technologies.  The Schaeffler approach nicely illustrates our conclusion that there is no single solution for meeting future fuel economy targets, and future vehicles will have to incorporate many small changes that will combine to deliver measurable results.  Schaeffler’s concept of creating a separate 48V accessory drive subsystem can keep costs manageable while allowing the industry to transition from 12V to 48V.

 

Quest for Aerodynamic Vehicles Faces Headwinds

— January 8, 2015

Although recent reductions in oil prices have slightly eased demand for more efficient vehicles, national governments are still pushing the rollout of more stringent emissions standards.  Because electric vehicles remain saddled with heavy, bulky, costly batteries,  the automotive industry is now investing in other technologies that improve the fuel economy of vehicles powered by conventional internal combustion engines that run on gasoline or diesel fuel.  Navigant Research has recently released a detailed report on this topic: Automotive Fuel Efficiency Technologies.

The report concludes that there is no single solution, and future improvements will be accomplished via many small changes that will combine to deliver measurable results.  Downsizing engines, adding turbocharging, reducing losses in transmissions, lowering mass, and improving aerodynamics will all make contributions.  The features that offer the largest benefit for the lowest cost will be implemented first.  What makes sense for a luxury vehicle may not be right for an entry-level car.  One of the primary avenues for fuel economy improvements is likely to be making cars more aerodynamically efficient.

Drag Reduction

Manufacturers must balance many factors, such as the customers who want better fuel economy but will not necessarily be willing to sacrifice performance to get it.  Less dense materials are more expensive than steel, and lighter vehicles must still meet all the relevant structural standards.  Ideal shapes for the best aerodynamic performance may be impractical to manufacture and difficult for people to get in and out of.

At an investor day hosted by Fiat Chrysler Automobiles in May 2014, the company outlined its new approach to global vehicle architectures.  In the presentation, engineers outlined their analysis of the relative importance of different factors affecting the amount of energy required to propel the vehicle.  The biggest factor in city driving was the vehicle weight, followed closely by tire drag and then aerodynamic drag.  On the highway, aerodynamics was the biggest factor, followed again by tire drag.

Lose the Mirrors

So it’s likely that aerodynamic performance will be getting plenty of attention for vehicles coming to market in the coming years.  Some features being looked at include active components, such as grill shutters that only open when cooling is needed, a feature that is already available on certain Ford Focus models in Europe.  Smoother airflow over and under the body and reducing the drag coefficient of the vehicle are options under development in both computer-aided analysis software and wind tunnels.

One of the easiest ways to reduce aerodynamic drag by 3% to 6% would be to eliminate external mirrors.  Tesla has been campaigning with the National Highway Traffic Safety Administration (NHTSA) to try to get the U.S. law changed to allow an external camera with an internal video screen as an alternative to an external mirror (as featured on its Model X design) and probably has support from many other original equipment manufacturers (OEMs).  Volkswagen is also pushing for change in Europe to expand the market for its ultra efficient XL1 vehicle that also has this feature.  If governments are serious about fuel efficiency, this would be an easy change to make by modifying the wording to require a rear view rather than specifying a mirror.

 

Wrightspeed Targets E-Truck Market

— December 30, 2014

The medium and heavy duty truck industry has tried for years to join the rush to powertrain hybridization and electrification with very little success.  The incremental cost has been difficult to justify for all but specific niche uses.  New market entrant Wrightspeed recognizes this situation, and it is targeting its new integrated powertrain at a specific type of fleet that uses medium duty trucks with high annual mileage (30,000-plus miles) and a drive cycle that includes a lot of stopping and starting.  The system is also suitable for heavy duty refuse trucks.  The design is essentially a plug-in all-electric drive with a range-extending engine to recharge the battery pack.

Founder Ian Wright, a member of Elon Musk’s original team that established Tesla Motors, has focused on developing a system that addresses a well-defined niche in the truck market.  Wrightspeed uses lithium ion (Li-ion) battery cells from A123 Systems to build a battery pack and installs its own thermal management system and charge management software.  Electric motors are built by a supplier to proprietary design specifications, and the control software is also developed in-house.  The system uses onboard individual wheel motors, and the software to control them is written by the company’s engineers.  Wright believes that it is important for a powertrain supplier to develop the complete system, not just improve individual components.

Weight Loss

The most dramatically different component is the choice of engine to provide charge to the battery pack.  Wrightspeed has gone with a microturbine from Capstone Turbine Corp.  This engine weighs approximately 220 lbs, about one-tenth of the mass of a typical diesel engine that can deliver similar power.  And because it runs at very high speed, the generator attached is only about the size of a 1-liter bottle.  The turbine can run on almost any liquid or gaseous fuel, and because of its burn efficiency, it does not need any exhaust after-treatment to remove toxic waste products.

Wrightspeed’s plan is to first address the replacement powertrain market for high-mileage medium duty trucks in large fleets, rather than aim at Tier One status with truck manufacturers.  Wright believes that, once fleet managers have had experience with the unique features of his system, his company will be able to move up.  Although it’s more expensive than a conventional diesel engine and transmission, the complete Wrightspeed solution of battery pack, electric motors, power electronics, and range-extending engine weighs about the same. The company reports substantial fuel savings from a combination of high-power regenerative braking and only running the engine in its most efficient mode.  Average fuel economy figures are estimated by Wrightspeed to go from 8 mpg to 10 mpg with a conventional powertrain, to 25 mpg to 30 mpg with its replacement system.  The powerful regenerative brakes also save significant maintenance costs for fleets, a major factor in the refuse truck market.

To date, Wrightspeed has reported orders for some test systems to be installed in garbage trucks, and FedEx ordered four units in February 2014, followed by an additional order for 25 more in July.  Deliveries are scheduled for the first quarter of 2015, and this new approach to hybrid trucks will be interesting to watch.

 

Getting the Most MPG

— October 23, 2012

In February 2012, a disgruntled customer won a small claims suit against Honda, claiming that the Civic Hybrid she bought never achieved the advertised 50 mile per gallon (mpg), which was the figure Honda claimed from the statutory EPA tests it is required to run.  The ruling was overruled in May by the Los Angeles County Superior Court, but spurred a number of additional claims in courts around the country.  The case emphasized the need for vehicle manufacturers to manage their customer expectations.

The EPA-mandated test was developed as a way for customers to compare vehicle economy by establishing a standard, supposedly typical, drive cycle for all vehicles.  If the cycle does not match your route and the way you drive, though, you won’t achieve the advertised number.   It was never intended to be a figure that all drivers would achieve.  (This factor is discussed in our recent report, Stop-Start Vehicles; under the EPA testing conditions, eliminating idling does not show any benefit for vehicles equipped with this system.)

Ford discovered this problem with hybrids after the launch of the first hybrid Escape in 2004.  The average driver thought that the technology would magically deliver better fuel economy regardless of how they drove.  So Ford quickly put together an event called the Escape Hybrid Experience to try to educate the owners.  Fortunately these were mainly early adopters who were keen to sign up, and the event was repeated at many locations all across the United States.

The key tactic in driving a hybrid is to make maximum use of the regenerative brakes, and avoid rapid acceleration as much as possible.  Gentle braking captures kinetic energy and stores it in the battery; heavy braking converts that energy to waste heat in the discs just as in a conventional vehicle.  Hybrids typically don’t do well at high speed, when the extra weight of the batteries and electric motor requires more energy to keep moving.  Driven gently, in stop-start traffic conditions, they deliver much higher mpg.

The MPG Marathon

Of course, driving in the recommended manner for hybrids will improve fuel economy for conventional vehicles too.  This was proved recently at an event in the United Kingdom, called the MPG Marathon, sponsored by ALD Automotive and Shell, among others.  In this annual test of driving skill and vehicle efficiency, drivers have to complete a course of 370 miles in normal traffic over 2 days, meeting timing restrictions that mean you cannot win by driving at 10 mph the whole way.  Vehicles must be in current production on the day of the event, and there are various vehicle categories for judging.

While best overall mpg is the goal of the event, the organizers also track the percentage improvement over the official mpg rating from the U.K. government standard test.  The overall winner this year was the Ford Fiesta ECOnetic, a small car with a 1.6-liter diesel engine, which achieved 108.8 mpg on a vehicle rated at 85.6 mpg under the official combined cycle test.  (U.K. gallons are larger than American gallons, but the economy is still impressive.)  Citroën’s Nemo won the van category, with 77.5 mpg.  Full results are on the competition website, but most manufacturers use the event to publicize their vehicles even if they don’t win: Toyota, Peugeot, Ford, Citroën, etc.

The conclusion here is that it’s not just the technology but how you use it that gets results.  And if you learn the correct technique and try hard, you can beat the official figures, and you don’t have to sue the manufacturer.

 

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