During starting of a turbocharged engine, should the waste gate be open or closed?

• A. Open, so as much exhaust as possible will bypass the turbine.
• B. Closed.
• C. Partially open.
• D. It depends on engine speed.

Answer: (A)

The main idea is that you want to minimize the turbocharger’s influence while the engine is just starting. The wastegate controls how much exhaust goes through the turbine. When you open the wastegate fully during starting, most of the exhaust bypasses the turbine, so the turbine doesn’t spin up aggressively and the engine faces less turbo drag and backpressure. This makes it easier for the engine to crank and start smoothly. As the engine comes up to speed, you can close or modulate the wastegate to let the exhaust drive the turbine more, building the boost you need for normal operation. Keeping the wastegate open during start prevents excessive boost and potential starting difficulties, whereas closing it would load the turbine more right away and could hinder starting.