Is Less More? - four-cylinder turbocharging engines

Automotive Manufacturing & Production, May, 2001 by Christopher A. Sawyer

Another benefit of electric drive, Garrett claims, is that excess energy can be redirected to the generator side of the system to provide electrical power. "We can use this to provide a source of extremely high voltage for hybrid electric vehicles," says Panella, "or use it as a supplemental 42-volt power source. That's the beauty of 'air on demand'."

The one question remaining is whether or not customers and OEMs will accept the cost and complexity necessary to do more with less displacement. "Over the past decade, we've seen an 18% reduction in displacement go hand-in-hand with an approximate 18% increase in power output," says Gillette, "and engines have gotten more costly and complex. So the argument can be made that customers and OEMs already have come to grips with this." Perhaps. But it remains to be seen if they will pay the projected $100 to $200 premium for electric drive with all the goodies.

Belting Out the Boost

Don't think For a moment that supercharging is losing favor as a way of boosting performance as automakers downsize their engines. "Over the next four years, we expect to see at least a doubling of our unit sales," says Ken Streeter, Eaton's supercharger sales and marketing manager. "Economy and emissions are the major drivers causing automakers to downsize their engines, but customers are demanding no loss in performance. That's caused a lot of interest in superchargers from nearly every manufacturer."

Eaton's largest supercharger customer today is Mercedes Benz. The company offers supercharged engines in its SLK, CLK, C-Class, and E-Class lines. GM is another large customer with supercharged variants of the Buick Regal and Park Avenue, and the Pontiac Grand Prix and Bonneville. Meanwhile, Ford offers the SVT Lightning--a pumped-up F-150--and Jaguar the XKR sedan and XJR coupe. Even BMW's Mini division will join the Fray with a supercharged Mini Cooper S. "We're working on approximately 20 new programs, including a number of diesel applications," says Streeter. But perhaps the greatest growth, at least in North America, will come in the light truck market.

Nissan's supercharged Frontier and Xterra are the first light truck applications (other than the limited edition Ford Lightning) to offer a supercharged engine as an option, but they doubtless will not be the last. "In the past, supercharging has been a pure power play," says Streeter, "but we see a definite move toward keeping a competitive power level while offering better fuel economy. Americans love torque, and smaller engines don't provide the performance buyers expect. Plus, a supercharger lets you get the torque up while running a (numerically) lower gear ratio for fuel economy." As for how quickly this shift will happen, Streeter says that depends on changes in CAFE legislation.

Like a turbocharger, a supercharger is under boost only 5% to 10% of the time. At Full boost, parasitic losses can reach 40 kW [depending upon the size of the unit, of course), dropping to less than 0.5 kW in non-boost conditions. But a supercharger has a few advantages over a turbo, says Streeter. "First, it doesn't soak up exhaust heat and delay catalyst light-off. Second, you can use it as an air pump on cold start. Third, you can choose one unit for a family of engines, and use different drive pulleys to alter the boost level--something I think we will see much more of. Fourth, it is emissions neutral, though you also can use it to put EGR back into the intake charge and homogenize the mixture. If there is a drawback, it's in having to pick up a [drive] belt line, but if you plan for a supercharger from the start, it's a clean installation." Packaging room, he claims, can be saved by integrating the unit into the intake manifold, like Cadillac did on its Evoq concept car.