Manufacturing Technology
economy. Jeff Jowett, manager–Americas Powertrain Forecast- ing for IHS Automotive concurred that boosting in general contributes to better fuel economy, in the right application. “Some people look at those stringent CAFE regulations com- ing up and immediately think electrification,” he said. “Tere are a whole host of technologies that will be important, and supercharging is certainly one of the pieces of the puzzle as OEMs assemble the right technologies to meet their needs.” To improve fuel economy, turbochargers seem to have
the upper hand over superchargers. Te engineers at Eaton, however, are quick to point out that supercharging offers many of the same advantages. “Tere was a time when people thought of superchargers as protruding from the hoods of race cars, like dragsters, where they gave more horsepower and enhanced performance [while using more gas],” said Tim Cavanagh, product line manager. “Eaton is in the process of changing that thought process, to thinking fuel economy. How? Trough downsizing the engine same as [is done with] turbocharging. A V6 with a supercharger can provide better fuel economy than a naturally-aspirated V8.”
and even other styles of superchargers lag behind in generating torque at those engine speeds. Tis is important in everyday use by real-life drivers. Future improvements may include a clutched supercharger that disengages the device when not in use, which can be up to 90% of the time for typical driving.
OEMs Select Superchargers As proof, Cavanagh said efficiency was the main attraction
for automakers choosing Eaton’s Twin Vortex Series super- charger. First introduced in 2007, it is now on vehicles like the Audi A7 3.0L V6, VW BlueMotion Hybrid with 1.4L I4, Golf GT, and the Nissan Micra with 1.2L I3. Tere are other practical advantages superchargers have
over turbochargers. Packaging and cost for assembly in the vehicle is competitive with turbochargers, according to Ca- vanagh, when the cost for all of the tubing and exhaust pipes included with turbocharger installs is taken into account. As a self-contained package, the Twin Vortex usually fits neatly into existing engine compartments. Another advantage is long-term maintenance. “Our superchargers are sealed packages, requir- ing no service or maintenance for the life of the vehicle,” said Cavanagh. He pointed out they use no special oil or air filters, either. Eaton is optimistic for the future. “We
are in a transitional phase, with busi- ness picking up in Europe, primarily,” he explained. Eaton believes the available market for boosting gasoline engines will grow from four-million boosted gasoline engines in 2010 to 17.5 million in 2017. Boosting in this context means either supercharging or turbocharging of any sort, for light vehicles. Light-duty diesel remains an untapped market for supercharging, with a potential size of 16.8 million by 2017, according to figures supplied by Eaton.
High levels of operator expertise and motivation, combined with uniquely designed equipment and software, means the Athens, GA, plant can produce several hundred thousand superchargers per year.
Downspeeding is the key. Supercharging allows an engine
to deliver the same torque as a normally-aspirated engine but at lower rpm—burning less fuel—to maintain horsepower. By downspeeding, a supercharger can improve fuel economy 15%, according to Eaton. “Tey are useful on hybrids, too, because with the supercharger you can tune the engines for maximum fuel economy,” he explained. Te Roots-style supercharger also offers these advantages at low engine rpm, where turbochargers
72 Motorized Vehicle Manufacturing
Better Design through Manufacturing Te Eaton Twin Vortex Series super-
charger represents the state of the art in a Roots-style system. Te essence of the
Roots-style is two counter-rotating lobed rotors that trap and push air as they rotate. Eaton’s Twin Vortex Series replaced an earlier three-lobe design with a four-lobe blower turned by a class 13 gear. Te blowers are solid components made from a special-
purpose aluminum alloy. Te tolerance in the interface fit between the two rotors is vital to making an efficient and quiet supercharger. “We used to use an epoxy paint that was baked hard on each rotor,” said Doug Brouillard, assistant engineering
Photo courtesy Bruce Morey
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