🔍 Key Concepts

• Look closely at the turbocharger in the illustration – note the flow path from the exhaust receiver, through the turbine wheel, and out the exhaust discharge. • Think about how gas flow works: for exhaust to pass through the turbine wheel, there must be a pressure drop across it; likewise, for air to be forced into the cylinders, the blower must raise the inlet manifold (scavenge air) pressure above atmospheric. • At rated speed and load, both the scavenge air and the exhaust gas are above atmospheric pressure, but they are not necessarily the same – consider which side has to "push" harder to drive the turbocharger.

💭 Think About

• On this engine, which component actually drives the blower wheel that compresses the intake air, and what does that imply about the pressure of the exhaust gas entering the turbine compared with the air entering the cylinders? • If exhaust gas did not have a higher energy/pressure than the air on the intake side, what would happen to the turbine wheel speed and the effectiveness of turbocharging at rated load? • During steady operation at rated speed, would you expect a consistent relationship between manifold air pressure and exhaust manifold pressure, or would it fluctuate randomly from cycle to cycle? Why?

✅ Before You Answer

• Identify exactly where the "common air inlet" pressure is measured in the illustration (after the blower/intercooler, before the cylinder ports). • Identify exactly where the "common exhaust outlet" pressure is measured (in the exhaust receiver/manifold before the turbine inlet). • Before choosing an option, verify which side – exhaust receiver or scavenge air manifold – must be at the higher pressure to maintain continuous flow through the turbine wheel and keep the turbocharger spinning at rated speed.