For four-stroke cycle engines, the inlet and exhaust valve opening and closing crank angles are typically: IVO 15  BTC; IVC 50  ABC; EVO 55  BBC; EVC 10  ATC. Explain why these valve timings improve...

For four-stroke cycle engines, the inlet and exhaust valve opening and closing crank angles are typically: IVO 15 BTC; IVC 50 ABC; EVO 55 BBC; EVC 10 ATC. Explain why these valve timings improve engine breathing relative to valve opening and closing at the beginnings and ends of the intake and exhaust strokes. Are there additional design issues that are important?