Exam Question

### (a) Advantages of Double Inlet and Exhaust Valves (6 Marks)
Fitting highly rated medium-speed engines with double inlet and exhaust valves (a 4-valve configuration) offers significant performance advantages, primarily related to improved engine breathing and thermal management.
1. **Increased Flow Area & Volumetric Efficiency:**
* **Geometric Advantage:** The total area available for gas flow through two smaller valves is greater than that of a single large valve that can fit in the same cylinder head space. The area of a valve opening is proportional to its diameter squared ($$A = \frac{\pi d^2}{4}$$). Two valves of diameter 'd' have a combined area greater than one valve of diameter '1.4d', which would occupy a similar chordal space in the head.