If the waste gate is closed, what is the effect on exhaust gas routing and impeller boost?

• A. Spill exhaust gases to the outlet
• B. Block exhaust flow entirely
• C. Increase backpressure
• D. Will force all gas to go through the turbine before entering the exhaust system, max driving power to the impeller

Answer: (D)

Closing the wastegate stops any exhaust from bypassing the turbine, so all of the exhaust gas must pass through the turbine. That means the turbine receives the full energy of the exhaust flow, causing it to spin faster. The faster turbine drives the compressor impeller more effectively, producing higher boost in the intake. In other words, you get maximum driving power to the impeller because none of the exhaust is diverted away from spinning the turbine; the gas then exits the turbine into the exhaust system downstream. The other ideas describe bypassing, blocking flow, or merely raising backpressure, which don’t reflect the effect of forcing all the exhaust through the turbine.