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From a piece reported at the Chicaco Auto Show by car.com:
Saab and Garrett Showcase Latest Turbocharging Technology
CHICAGO — Turbocharging is nothing new at Saab. In fact, the Swedish automaker has worked with the Garrett company since the 1970s, cooperatively developing the first turbocharged automobile engines. Saab adopted turbocharging not only for its production models but for its motorsports activities through the years.
Known in the past as Garrett AiResearch, the company — now a division of Honeywell — has evolved into Garrett Engine Boosting Systems. With facilities throughout the world, it’s the largest manufacturer of turbochargers, which are devices that force a stronger charge of air into an engine to mix with more fuel and increase power output.
Unlike superchargers — which have a mechanical connection to an engine’s crankshaft that robs efficiency — turbochargers are driven by the rush of the engine’s exhaust gases, so their operation directly relates to engine speed. Turbos of the past were impaired by “lag.” Instead of producing their maximum boost swiftly, turbochargers took a moment — typically, more than a moment — to reach their peak. Drivers would be well aware of the delay when tromping on the gas pedal, only to receive an unpleasantly delayed response — at the exact time when an extra burst of power was most needed.
Turbo “lag” is a lot less troublesome these days, but the Garrett company is taking its technology one step further by means of electronic control. The result is what Robert J. Gillette, president of Garrett Engine Boosting Systems, calls “air on demand.” Rather than rely solely on exhaust-gas flow, a high-speed electric motor is set up to drive the turbocharger’s shaft automatically, whenever needed. The electric motor kicks in while the engine is running at low speed but releases its hold as the engine turns more rapidly. This can yield a smoother, more seamless blast of power for passing or merging.
An electronically assisted system can “provide boost whenever you want it, exclusive of engine speed,” Gillette said. Full engine speed arrives in less than a second, by use of the electric motor. Electronically assisted turbocharging will be installed in 2003 Saab models. Garrett also works with the “top 10” global automakers, including Volkswagen, BMW, DaimlerChrysler, Ford, General Motors and Toyota. In Europe, Gillette said, turbochargers are used in diesel engines. Diesels are popular in Europe due to their frugal fuel economy ratings, though less so in the United States.
“The only way to really get economy is to go down in engine size,” Gillette said. That’s a big advantage of turbochargers. When the need arises, the driver of a car with a turbo-equipped, small-displacement engine can enjoy a beneficial power boost. But when the crucial situation has passed, the turbocharger ceases to push air forcefully and the engine reverts to normal operation, yielding the economical mileage figures that only a small engine can provide.
Partly because of this improved efficiency of turbocharging, average displacement of the world’s engines has declined by 18 percent over the past decade. During that same period, the specific horsepower of those global engines has grown by about 18 percent. This phenomenon, Gillette believes, “is a trend for the future that will continue.”
To help showcase its interest in turbo technology, Saab exhibited the racing 9-3 Viggen that was driven to history by Per Eklund in the most recent Pike’s Peak Hill Climb. With its 2.0-liter engine developing 750 hp, the race-fitted Saab can accelerate to 60 mph in a surprising 2.2 seconds.
, Wed, 21 Feb 2001 15:29:33
, Thu, 15 Feb 2001 09:42:57, Sun, 18 Feb 2001 15:36:10, Wed, 14 Feb 2001 09:09:28, Wed, 14 Feb 2001 09:08:42, Wed, 14 Feb 2001 15:53:02, Wed, 14 Feb 2001 16:42:03
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