🔍 Key Concepts

• Relationship between turbocharger compressor air flow and what drives the turbo (exhaust gas energy) • How engine speed and engine load each affect exhaust flow and turbo speed • Difference between something being directly proportional versus just being related

💭 Think About

• Ask yourself: which variable changes in a nearly straight-line way with the amount of air the turbocharger supplies to the engine cylinders? • Think about what physically makes the turbocharger spin faster or slower—what increases the mass flow of exhaust gas through the turbine? • Compare how exhaust pressure, exhaust temperature, speed, and load each behave as the engine is opened up from idle to full power—does any one of them stay in a clean, proportional relationship with intake air flow?

✅ Before You Answer

• Be clear on the meaning of directly proportional (if one doubles, the other doubles). • Consider which option is the primary control variable used by engineers to describe air flow through an engine and turbo. • Mentally plot each choice versus air flow from low to high power and see which one looks closest to a straight-line relationship.