Like it or not, forced induction is the future of the internal-combustion engine. General Motors knows this, and that’s why a number of its models have adopted at least one turbocharged engine option. Now the company has filed a patent with the United States Patent and Trademark Office that may signal the company’s next steps in turbocharging technology.
Titled “Internal Combustion Engine Having a Two-Stage Turbocharger,” the patent outlines a potential means of taking maximum advantage of the energy available in the exhaust stream with a two-stage, twin-turbo setup using turbochargers of different sizes.
While this basic premise isn’t new, GM’s proposed means of managing the pair is. Relying on an ECU that is constantly measuring engine speed and load, GM’s patent suggests equipping two-stage twin-turbocharged engines with a pair of butterfly valves operated by an electronic actuator. These valves are used to control exhaust flow to the two turbos. Both valves are mounted on a common shaft so that when the actuator closes one valve, it simultaneously opens the other (and vice versa). Such a system allows the smaller, quicker-spooling turbo to operate at lower engine speeds and the bigger turbo to come online during events that call for higher engine speeds. In short, it works much like any other two-stage twin-turbocharged engine.
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