"Optimal combustion" refers to the best condition or process where fuel burns efficiently. It means achieving the most effective and complete burning of fuel, resulting in greater energy production and lesser waste or pollution. Full definition
MultiAir technology helps maintain optimal combustion at any speed under any driving condition. (dodge.com)
An air induction humidity sensor ensures optimal combustion efficiency, regardless of the surrounding air's humidity; (greencarcongress.com)
The IACV controls air flow at cold start to give enough air because the engine is not warm enough for optimal combustion, so, you need more fuel and consequently more air to get enough fire to warm up the cold engine components. (mechanics.stackexchange.com)