Navigant Research Blog

Electric Turbochargers: The Next Big Thing in Fuel Efficiency

— October 23, 2014

The key to the next major advance in internal combustion engine fuel efficiency could well be the electric turbocharger.  At a recent fuel economy technology showcase at the U.S. Environmental Protection Agency (EPA) National Vehicle Emissions and Fuel Lab in Ann Arbor, Michigan, Valeo showed off the motor-driven turbo it will supply to an unannounced automaker.  The first production applications are scheduled to begin arriving in 2016, according to the company.

The aggressive expansion of fuel efficient technologies, such as electrification, multi-speed automatic transmissions, and engine downsizing, has played a major part in increasing miles per gallon.  The average fuel economy of the American new light duty vehicle fleet has improved by almost 25% over the past decade.  Meanwhile, gasoline direct injection and turbocharging have enabled engineers to cut engine displacement by 30% or more without sacrificing the performance that drivers have come to expect.  As of the 2014 model year, approximately 75% of Ford gasoline and diesel engines globally are turbocharged while 85% of Volkswagen engines are boosted.

Response Time

Part of the concept behind boosted engines is to use smaller engines with turbochargers that provide performance on-demand.  There has always been an inherent time lag, however, between the time the driver presses the accelerator and the generation of enough extra exhaust gas to spin up the turbo and provide boost.  Mechanically-driven superchargers eliminate much of the lag at the cost of substantial friction at higher speeds.

Replacing the exhaust-driven turbine side of the turbocharger with an electric motor provides a number of advantages, most notably in packaging, responsiveness, and operational flexibility.  One of the fuel economy benefits Valeo highlights is the combination of an electric turbo with the cylinder deactivation – i.e., the ability to shut off multiple cylinders under light loads in order to improve fuel efficiency.

The fuel savings achieved by shutting off unneeded cylinders can be quickly lost when driving on roads that aren’t completely flat.  Even a mild grade can cause an engine to switch back to running on all cylinders in order to produce enough torque to maintain speed.  “With an electric turbo, the engine management system can request small amounts of boost on-demand to increase torque while climbing a grade while keeping as many as half of the cylinders inactive,” Ronald Wegener, application engineering manager with Valeo, told me.  “This can yield up to a 10% improvement in efficiency.”

Valeo has developed versions of the device for both 12V and 48V electrical systems so that the turbo can also be used as part of a mild hybrid system during off-throttle conditions.  Intake air flowing through the compressor drives the motor to generate electricity, charging the battery.  Audi is using this as one of the two forms of energy recovery on its Le Mans-winning R18 e-tron race car.  Many of the current crop of Formula One cars have also adopted this approach.  Earlier this year, Audi announced that the next-generation Q7 TDI, scheduled for model year 2016, would be its first production application of the technology.

Shrinking Engines

Electric turbochargers also provide packaging benefits to engine designers.  Traditional turbos require complex plumbing to route exhaust gases to the turbine side of the turbo and feed the boosted intake charge to the other side of the engine.  Disconnecting the turbo from the exhaust allows designers to place the turbo wherever it fits best for packaging and performance.

Executives and engineers agree that while electric vehicles will gain market share in the coming years, internal combustion engines will likely remain the dominant powertrain choice in the transportation space at least through the 2020s.  With engines continuing to shrink, it seems likely that electric turbochargers will account for a growing share of the boosted engine market in the next decade.

 

Truck Fuel Economy on the Rise

— October 20, 2014

The U.S. Environmental Protection Agency (EPA) has just published its 2014 fuel economy trends report, and though the news is generally positive, some potential storm clouds remain on the horizon for manufacturers.  While the overall average fleet fuel economy hit a record 24.1 mpg for the 2013 model year, the monthly update from the University of Michigan Transportation Research Institute (UMTRI) showed a 0.5 mpg drop in September 2014, equal to the 2012 to 2013 annual increase.

The long-term trend has definitely been upward.  Last year represented the eighth increase in the past 9 years for the American new vehicle fleet.  Automakers will have to maintain this momentum if they expect to hit the 2025 corporate average fuel economy target of 54.5 mpg.  Fortunately, attendees at a fuel economy technology showcase at the EPA emissions testing lab in Ann Arbor were all publicly confident that the targets were achievable.

As for the sudden drop in September, that can be explained by what are likely temporary market conditions that led to a significant uptick in full-size truck sales at General Motors (GM) and Chrysler.  As the 2014 model year drew to a close, combined sales of the Chevy Silverado and GMC Sierra jumped 46%, aided by incentives of up to $4,500.  Ram sales were also helped along by retail incentives of up to $3,000, as well as the popularity of the new Ram 1500 EcoDiesel.

From Steel to Aluminum

Sales of Ford’s F-series trucks were essentially flat, as the automaker began the transition to its all-new, aluminum-bodied 2015 F-150.  It appears that GM and Chrysler are hoping to grab some market share in the financially lucrative big truck segment in hopes that Ford would stumble in the complicated transition from steel to aluminum trucks.

At this point next year, even if truck sales continue to climb, we’re unlikely to see a similar drop-off in fuel economy, thanks to new technology in the segment.  The weight savings and new power plants for the Ford trucks are projected to deliver up to 20% better fuel efficiency than the steel-bodied versions.

Chrysler and GM also have to meet the new fuel economy standards.  Ram pickups are already available with ZF 8-speed transmissions, and GM is adding its first 8-speed automatic transmission to 2015 pickups with a 6.2-liter V8.  As GM ramps up production of the new 8L90 transmission, it will probably get paired with other engines as well.  GM and Ford also have a joint development program to produce 9- and 10-speed transmissions for trucks and other vehicles in the next few years.

Diesel Debuts

Chrysler is also building on the success of the 28 mpg Ram 1500 EcoDiesel by doubling production to 20% of its total production volume of trucks in 2015.  Ford is still awaiting final EPA certification on the 2015 F-150, but the 2.7-liter EcoBoost V6 is also expected to get a highway rating in the upper 20s.  GM’s new midsize Colorado and Canyon pickups are already rated at up to 27 mpg with a gasoline V6, and a diesel version is coming some time in 2015.  Ford is also offering a diesel engine option in the new Transit full-size vans that replace the E-series this year.  Ford will likely be closely following the sales trajectory for diesel engines in the Chrysler and GM trucks, as well as the next-generation Nissan Titan and Toyota Tundra, which will both be available with a Cummins-sourced 5.0-liter diesel V8.

With the huge sales volumes of pickup trucks in North America, lightweighting, advanced powertrains, and automatic stop-start, trucks will make a big contribution to reducing fossil fuel use in the next decade.

 

Autonomous Vehicles Will Work Best Within Limits

— October 1, 2014

About the only way your next car has much chance of driving itself is if you live in a gated community or on a college campus where it won’t have to deal with too many variables like other traffic.  Just as voice recognition systems work best with limited vocabularies, autonomous vehicles will probably be limited to such constrained environments for the foreseeable future.  That’s the conclusion from the recent ITS World Congress 2014 in Detroit.  Increasing levels of vehicle automation were a major topic of discussion during the annual conference on intelligent transportation systems.

Google has been pushing the idea that self-driving vehicles will hit the road within the next 5 years.  Google had no official presence at the conference, but a lot of companies that build cars, parts, and infrastructure systems were there, and no one that I spoke with was in agreement with Google’s timing projections.  The general consensus is that we won’t see widespread use of full operating range autonomous vehicles until closer to 2030.

Not Street-Ready

That’s not to say that no one believes in automated driving; quite the opposite.  It’s just that in engineering circles, there’s a rule of thumb known as the 90/10 rule.  That is, 90% of the technical challenge of a project takes about 10% of the time and effort.  The last 10% takes the other 90% of the time.  In the realm of self-driving cars, we have just begun that last 10% phase, where the basic hardware elements are all worked out but a lot of software decisions have yet to be made in order for autonomous systems to be truly robust.

Much of the on-road development by Google and other companies has been occurring in places like California and Nevada, where environmental factors like snow and even rain are a rarity.  In order for autonomous vehicles to be both commercially and legally viable, they’ll have to work reliably under any weather and road conditions.

General Motors (GM), Volkswagen, and other automakers have been working on autonomous technology much longer than Google, and they understand these limitations.  When GM rolled out a two-seat self-driving pod car known as the Electric Networked-Vehicle, or EN-V, at the 2010 Shanghai World Expo, program leader Dr. Chris Borroni-Bird acknowledged that, while this type of vehicle would eventually be an ideal way to deal with the congestion problems of megacities like New York, Shanghai, and Mumbai, the first feasible real-world applications were likely to be in restricted environments, such as campuses and gated communities.

Say Again

As powerful as computers have become, they still don’t deal with the nuances of the real world very well.  That’s why voice recognition systems still struggle to understand what should be simple natural language commands on a smartphone.  The most successful applications of the technology have been for tasks like medical transcription, with limited and specific word vocabularies and little ambient noise.  Similarly, automated vehicles function best in constrained spaces, such as buses over fixed routes or the aforementioned commuter pods.

Google hasn’t actually made any major breakthroughs in the technology that we know of.  It just jumped into field relatively recently, hiring many of the engineers and scientists that worked on the autonomous vehicles fielded by automakers in the DARPA Grand Challenge and Urban Challenge competitions of 2006 and 2007, and leveraging the cost declines of the required sensors.

Where Google has outdone the incumbents is getting the technology media to talk about their efforts – but that’s unlikely to put full-function self-driving cars into consumers’ hands any sooner.

 

A Few Steps Closer to Autonomous Vehicles

— September 30, 2014

As engineers, scientists, executives, and government officials involved with transportation systems gather in Detroit this week for the annual ITS World Congress, the auto industry took another incremental step along the 60-plus-year road to autonomous vehicles.

In her keynote address, General Motors (GM) CEO Mary Barra announced that two of the technologies that are building blocks toward a driverless future will come to market in 2016.  The 2017 Cadillac CTS will be the first production car from GM equipped with vehicle-to-vehicle (V2V) communications technology.  Barra did not provide any details about exactly what sort of information would be exchanged between cars equipped with the technology, but messages will likely include alerts about brake applications, slippery road conditions, and position and speed as the vehicle approaches an intersection.

GM is the first automaker to announce that it will equip a production vehicle with V2V technology, but it’s likely that other premium brands will soon follow suit, especially now that the U.S. Department of Transportation has begun the process of writing rules to mandate the technology in the coming years.

Beyond Cruise Control

Barra also announced that a new Cadillac model that has yet to be revealed will be the first car in its lineup equipped with super cruise technology.  Super cruise is a semi-autonomous highway driving mode that combines advanced radar-based adaptive cruise control with upgraded camera-based lane-following capability.  In traffic, the system is able to bring the car to a full stop, automatically restarting as soon as the leading car moves.  GM first demonstrated super cruise to media in 2012 and has continued to refine the system.

In the days before the official opening of the ITS World Congress, Toyota held a separate advanced safety systems seminar where it demonstrated a system very similar to super cruise installed in the Lexus GS 450h.  The system also includes the capability to determine which lane the car is in to provide the driver with alerts for potential hazards, such as traffic merging from the left or exit-only lanes.  GPS doesn’t provide enough precision to determine which lane a vehicle is in, and Toyota engineers declined to provide specifics, but the system almost certainly uses the new higher-fidelity camera that is installed as part of the lane-tracking system.

Driver Still Required

Toyota also announced that this system would be coming to market very soon, but would not be as specific as GM.  During the technology demonstrations at the congress, Honda also demonstrated its own automated highway driving system, although it has not yet announced when the system will reach production.

The key to these systems is that they do not completely replace the driver, but simply reduce the workload during some of the more monotonous aspects of highway driving.  Unlike Google, which is extremely bullish on autonomous vehicles, traditional automakers, which are more familiar with the realities of putting high-technology cars in customers’ hands, are taking a much more cautious approach.

 

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