While building millions of pickups with aluminum bodies certainly signals a good-faith effort at boosting fuel economy, that ambitious program alone won’t achieve Ford’s total CO2-reduction goal. So the company has teamed up with Magna and, with the assistance of some U.S. Department of Energy grant money, embarked on a project to reduce the weight of a midsize family sedan by 25 percent using technologies that are production feasible today (so no 3D-printed carbon-fiber birdcage unibodies).
The resulting Multi-Material Lightweight Vehicle (MMLV) Concept achieves a 23 percent overall reduction to roughly the mass of a Fiesta sedan, with all areas of the car participating in the diet (body exterior 23 percent, interior and climate controls 22 percent, chassis 28 percent, powertrain 21 percent, and electrical 14 percent). Magna’s contribution was primarily lightening the body exterior and closure panels, prototyping, and CAD/CAE work with Ford handling most of the rest of the project. Below are highlights of the more innovative reductions, many of which could see production in the relatively near term.
Body and Closure Panels
The 2014 Fusion already employs a great deal of high-strength steel, and the front crash structure, A-pillar and side roof rails are retained. The B-pillars and the roof crossmember connecting them are made of high-boron press-hardened steel. Advanced vacuum die-cast aluminum castings and aluminum extrusions comprise much of the rest of the unibody structure. It’s all joined using a combination of welding, adhesives, and self-piercing rivets. Body structure savings: 76 kg, 24 percent. The doors incorporate boron-steel intrusion beams, extruded aluminum hinge-pillar reinforcements, high-pressure vacuum die-cast magnesium nodes joining the A-pillar to the lower door, and stamped aluminum inner and outer skins. Closure Panel savings: 29 kg, 30 percent. Changing to chemically hardened “Gorilla glass” for the side windows would realize a further 35% savings. Note that the Transit Connect’s rear cargo door glass is being replaced by polycarbonate, for an even greater savings, but that material isn’t ready for side windows yet. Finally, switching from steel to cast and extruded aluminum in the front and rear suspension cradles saved 27 kg, 48 percent.
Switching from steel and plastic to a carbon composite material for the instrument panel and cross-car beam saves 5.2 kg, 17 percent in mass and also trims the parts count from 71 parts to 21, realizing further cost savings. Doing the same for the front seat frames saves 0.8 kg, 17 percent, and it should be noted that these seat frames are made somewhat like the chassis tub of a Lamborghini Aventador, with dry fabric laid in a mold and then injected with resin. Note that Ford is working with Dow Chemical to lower the price of the carbon fibers themselves.
Lighten up the body and you can lighten the chassis components, and reducing unsprung weight generally improves ride and handling. Lightening things that rotate add yet another contribution to fuel economy/performance improvement in reduced rotational inertia. Chassis highlights include tall, thin 155/70R19 tires (3.6 kg, 31 percent each) riding on 5.0 x 19-inch carbon-fiber wheels (4.5 kg, 42 percent each). The wheels may be the least production-ready cost-feasible parts on the concept car. Aluminum brake rotors get a stainless steel thermal coating that is machined to 1mm thick. Rather than grinding them at service intervals, a new coating might be applied. Front rotors save 3.5 kg, 39 percent each, rear rotors save 1.9 kg, 37 percent each. Composite front coil springs save 1.6 kg, 57 percent and have been subjected to extreme tests like soaking them in water for hours, then deep freezing them, and torture testing them. So far so good, but trials on test cars have yet to begin. Hollow steel tubes form the rear springs save 1.6 kg, 37 percent each. Not enough? Titanium rear coil springs save 2.3 kg, 54 percent each.
With all the other weight savings onboard, less engine is needed to motivate a family Fusion, so the 1.0-liter EcoBoost I-3 is fitted, but with a bunch of further upgrades. The biggie is swapping cast iron for aluminum with compacted-graphite iron inserts to help tie the head bolts to the crankshaft bearings, so the engine block saves 45 percent. The cylinders themselves get an iron coating sprayed on. Forged aluminum connecting rods save 0.45 kg, 40 percent total, and permits hollowing out and lightening the crankshaft, saving 1 kg, 17 percent. Aluminum castings are currently used for the structural front engine cover (to which an engine mount bolts), and the oil pan. Making these of injection-molded carbon fiber drops the weight of the engine cover by 1 kg, 24 percent and the oil pan by 1.2 kg, 40 percent. Note that this is an injection process that includes chopped carbon fibers—not a hand-laid, or fabric-in-mold injection process. Switching from aluminum to magnesium for the transmission case and bell-housing saves 5 kg, 33 percent; doing the same for the valve body saves 0.9 kg, 34 percent; ditching cast iron for 390 aluminum on the pump support saves 2.5 kg, 60 percent. Another two-fer comes from swapping steel for 7000-series aluminum (still with a steel gear at the center) on the clutch hub, saving 0.4 kg, 55 percent, and getting a dramatic drop in rotational inertia.