CHICAGO - Using a small high-revving electric motor, Garrett Energy Boosting Systems is looking to put a new - and faster - spin on the old-fashioned turbocharger.
By adding a small electric motor to the turbocharger, Garrett seeks to overcome turbo lag, the time delay until a turbocharger becomes effective caused by waiting for the engine's exhaust stream to speed up the device's turbine.
Garrett's electrically assisted turbocharger will increase fuel economy and performance, Rob Gillette, president of the Torrance, Calif., company said at a press event during the Chicago Auto Show.
Gillette said the electronically assisted turbocharger will be used in a 2003-model car but would not name the automaker.
Jury's still out
Opinions differ on whether such a device is needed.
Saab, which allowed Garrett to use its display area at the Chicago show for a press conference, is evaluating the technology for its next generation of engines, spokesman Kevin Smith said. Garrett says the electric-assisted turbo is best suited for 1.8- to 3.0-liter gasoline and diesel engines.
But Fritz Indra, executive director of advanced engineering for Saab's corporate parent, General Motors, is not convinced adding electric power to a turbocharger is a good idea.
'With a very good modern turbocharged engine, you don't have lag anymore,' Indra said. 'An engineer's task is to avoid complexity and go simple and safe.'
Indra says the electrically assisted turbocharger would use a lot of power, and he sees potential trouble connecting electrical cables to a part of the engine that gets so hot. He says Opel's new turbocharger, which is built into the exhaust manifold, is a good example of improving the turbocharger without making it more complex.
Cost could also be an issue. Garrett's electric turbocharger will add $100 to $200 to the cost of a car, Gillette said.
A turbocharger is a pump mounted in the exhaust system, usually just below the manifold. Exhaust gases spin a fan-shaped wheel, which spins another fan-shaped wheel in the intake system to blast a denser mixture of fuel and air into the engine to increase performance.
Turbochargers were used widely in the late 1970s and early 1980s as automakers tried to balance consumer demands for more power with the need to use smaller engines to meet fuel economy mandates. But some units were prone to early failure because of the heat generated by the exhaust gases and the turbo unit.
Today turbochargers are used in Saab, Volvo, Volkswagen and a few other import vehicles in the United States. Ford Motor Co. and GM use turbos on their diesel V-8 truck engines.
How it works
Here's how the electric turbocharger works:
An electric motor mounted on the shaft between the compressor and turbine wheels quickly brings the turbocharger up to speed. The motor eliminates turbo lag, so there's an instant blast of power at low engine speed. The car's electronic control unit controls the turbocharger. The control unit also governs the boost pressure - the amount of fuel and air mixture the turbocharger pumps into the engine. The electric motor also doubles as a generator, producing electricity from the spinning turbo at cruising speeds. It can supply up to 1.3 kilowatts at 13.5 volts, according to Garrett.
Gillette said it will take the electric turbocharger less than a second to get up to full speed, down from about 3.5 seconds of a regular turbocharger. That will enable the engine to develop more torque at lower speeds and improve fuel economy, Gillette said.
Gillette said the same technology also will be used on superchargers, which are mechanically driven pumps. Gillette said Garrett plans to have an electrically driven supercharger ready by late 2004.