Fuel Economy and Lightweighting Insights

By on February 5, 2019 in DESIGN/MODELING/SIMULATION

What the switch to crossovers means—and much more.

Two events last year dove deep into the realm of lightweighting—what’s happening now and what to expect down the road.

In December, Ward’s Auto hosted a seminar on fuel economy and lightweighting. The overarching message stems from changing consumer behavior, away from small vehicles and instead, purchasing vehicles that are larger and allow the driver to sit higher from the ground. By 2025, many predict that at least 50 percent of new vehicles will be crossovers. Although certainly, the larger SUVs and pickups represent significant market share, as well.

A lot of the crossovers that were studied share the same powertrain and chassis as a sedan made by the same manufacturer. Because sedan sales have plummeted, many of those programs have been canceled. The average engine size in these crossovers is 2.3L, 4 cylinders and the common transmission an 8-speed. Crossovers are larger than sedans, about 300 pounds heavier, and the aerodynamics is not as good as the low-profile sedan. Combining those factors, the transition to crossovers also correlates to a reduction in fuel economy on the order of 3 to 6 percent.

The current corporate average fuel economy (CAFE) regulation aiming toward 54.5 miles per gallon by 2025 is up for debate. The California Air Resources Board (CARB) would like to maintain an aggressive target. On the other side of the spectrum, the Trump administration is promoting its proposed Safer Affordable Fuel Efficient (SAFE) Vehicles resolution that amends the CAFE fuel-economy target, which would proceed to 2020, then freeze at that level.

The Alliance of Automobile Manufacturers suggests meeting in the middle, with increasing fuel-economy levels that are not as extreme as the current rate and flexible enough to compensate for the uncertainty of market acceptance of electrified vehicles.

What are the major levers to adjust vehicle fuel economy?

  • Engine
  • Transmission
  • Aerodynamics
  • Weight

The powertrain plays a significant role in fuel economy, and there are many new developments that are gaining acceptance. 12V start/stop function is now on 30 percent of engines. Combustion is studied every day. Turbo systems were viewed early on as problematic, and now their popularity is skyrocketing globally. And 48V mild hybrids are taking hold. Eight-speed transmissions will replace the 6-speed. Pickup trucks are using 10-speed transmissions.

Aerodynamics contributes a significant role in fuel economy. Yet replacing sedans with higher-standing crossovers and SUVs results in higher drag coefficients and reduces the mileage. Auto manufacturers address the drag coefficient with styling, such as roof-rack profiles that cut through the air. A fairly recent development is active grille shutters that can deliver a 30-count improvement in drag coefficient.

New efforts are focusing on managing airflow underneath the vehicle. At Lightweighting World Expo 2018, Superior Industries mentioned their efforts to design wheels that reduce the aerodynamic drag. Aerodynamic wheel covers are used in the commercial truck market, but they are unattractive and not likely to take hold in the consumer vehicle market.

The 300-pound weight increase correlates to 3 to 6 percent reduction in fuel economy. There are many options to reduce vehicle weight—high strength and highly formed sheet materials, extrusions, castings, composites, molded inserts, polycarbonate glazing and joining technologies to name a few. They all come at a price, along with degrees of change in the manufacturing and integration process.

At the Ward’s Auto seminar, Shiloh Industries claimed they can cut 100 pounds from every vehicle at no additional cost. Shiloh is one of few suppliers who delivers vehicle components in steel, aluminum and magnesium, sheet and cast products. They highlighted the industry-first squeeze cast aluminum rear axle carrier for a GM truck, translating into 25 pounds of weight savings.

ArcelorMittal and Nucor discussed many cost-effective options for cutting weight. The new generation of steels can be hot formed and deliver strengths on the order of 2000 MPa—so impressive! The tailor welding process allows the placement of different materials in different locations. Imagine a door frame made by five or six different stampings varying by thickness, strength, even having galvanizing—all laser welded. Then comes the real magic, forming over a tool in one step.

This is not a new offering per se, yet give credit to the auto industry for making it reliable and cost effective. Steel companies are constantly innovating on new materials and processing, with of course, the focus on process reliability.

Several Ward’s presenters addressed the mission to reduce part count. Martinrea, a global leader in subframes, gave an example of a 40-to-50-piece steel welded frame converted to a one-piece aluminum casting. The cast shock tower, which is common in Europe and gaining in popularity in North America, is produced as a structural (high elongation) aluminum die casting to reduce piece count from nine to one. The aluminum shock tower provides on the order of 10 pounds of weight savings. To address tool life, and exploit low density, Shiloh is investigating cast magnesium shock towers.

One-third of the makeup of a car is polymer, plastics or composites. At the Lightweighting World Expo, Mark Voss, engineering group manager at General Motors, discussed the impressive work done on the pickup bed for the GMC pickup—durable, lightweight and with features that will drive sales.

Continental Structural Plastics produces that bed, and they have been delivering sheet molded composites (SMC) for decades. They are now seeing increased demand for new materials globally with the push for improved vehicle efficiency, noting the development of electric-vehicle battery boxes with lower tooling than metal designs, recycling friendly, corrosion resistant and good performance in the fire testing.

The new year of 2019 is upon us. The move toward lightweighting always begins with “where can I cut weight at no cost?” and extends to the premium applications. I still think the five to six pounds of weight savings available via aluminum calipers is a cost-effective idea, even though it was not very popular on the 38 crossovers and SUVs in the Mayflower Consulting “Automotive Suspension & Wheel-End” study. (https:/lightweighting.co/market-research/)

The automotive market is particularly challenging because the designs today are not coming to the dealership until ’22-23, and then they will last seven years. How to predict the future? Those of us tracking lightweight materials and processing see a bright future—keep your focus, identify your lane (the vehicle that needs your offering), and deliver great customer service.

Last, the Lightweighting World Expo 2019 will be held Oct. 8-9, 2019, in Novi, Mich. (www.lightweightingworldexpo.com). The inaugural show in 2018 was a great start with many positive comments from speakers and attendees, alike. The Q&A after each speaker was especially popular, as was the broad coverage from body/closures to fastening, powertrain to additive manufacturing. We welcome your feedback on what you would like to see at the 2019 Expo, and of course, we hope that you can join us.


By Andrew Halonen, president, Mayflower Consulting

Andrew Halonen is president of Mayflower Consulting, LLC, a lightweighting consultancy that provides strategic marketing, market research and business development for high-tech clients in automotive, defense and commercial trucking. Mr. Halonen works with castings, composites, additive manufacturing and new material development programs. www.lightweighting.co