Incylinder

In-cylinder, sometimes written as incylinder, is a term used in automotive engineering to describe processes, measurements, and phenomena that occur inside the combustion chamber of a piston engine. This space is defined by the cylinder bore, piston, and cylinder head and is where air, fuel, and combustion gases interact during compression, ignition, and expansion.

In-cylinder analysis often centers on pressure and temperature within the chamber. In-cylinder pressure is measured with fast-responding sensors and used to generate pressure-time traces, from which indicators such as indicated mean effective pressure (IMEP), heat release rate, and combustion phasing can be derived. These measurements support engine development, calibration, and model-based control strategies.

The specific in-cylinder processes vary by engine type. In spark-ignition engines, air and fuel mix and ignite within the cylinder to produce combustion. In diesel engines, injected fuel interacts with hot compressed air and auto-ignites. Direct injection, port fuel injection, and stratified charge concepts alter in-cylinder mixing and combustion efficiency. Design features such as piston bowl geometry, valve timing, compression ratio, and cylinder head design influence in-cylinder pressure and temperature profiles, affecting performance and emissions.

In-cylinder phenomena are closely linked to emissions formation, including NOx and particulates, and to fuel efficiency. Understanding in-cylinder conditions enables optimization of ignition timing, fueling, and advanced combustion strategies, as well as diagnostics and control in modern engines.