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Turbulence in the combustion chamber do to this squish helps with Fuel air mixing, wall heat transfer, Thermal efficiency, and overall engine performance. Heat transfer is aided when the combustion air is swirled around and pass by the cylinder wall helping transfer the heat to the cooling system more efficiently. This efficiency and swirling can also reduce the amount of soot production.

Squish effect may be found in any fuel type internal combustion piston engine. Squish piston engines are also found in both two stroke and four stroke engines.

Design Types
Squish piston engine are achieved by modifying an engines head, block, or the piston crown. Some engine designs include combinations of these different design types. These combinations are used when certain design parameters that attribute the the shape and constraints of the combustion chamber

Modified Head
Modified Head squish piston engines utilize a space in the head to make an pocket for squishing and combustion to occur. Depending on the shape of the pocket and what type of engine, The valve position must be skewed to ensure that both the intake and exhaust valve can fit in the pocket. Modified Head squish piston engines can also be made to fit the application on a Flathead engine as well as Overhead cam and two stroke engines.

Modified Block
Modified Block squish piston engines utilize a space in the block to create a pocket for squishing and combustion to occur. These squish piston engines are otherwise referred to as flat head engines. These types of engines are not very common anymore because of the inherent issues with insufficient air flow into the engine which directly affects the compression ratio. This design is mostly used in small, low cost applications.

Modified Piston
Modified piston squish piston engines utilize a space in the piston to create an air pocket for squishing and combustion to occur. These pockets can be made by making a recess in the piston crown. This is called a deep bowl piston. Others may use raised areas relative to the piston rings to create a different effect in the combustion chamber This creates a different type of turbulence that goes down instead of up in the piston itself. To promote turbulence and mixing of the fuel air ratio, the piston crown must have a recess parallel to the angle that the fuel is injected. It also requires a curve on the outer section of the piston crown. This design directs air from the squish area into the center of the combustion chamber. This is where the squished air is mixed with the fuel from the injector creating a more evenly mixed fuel to air ratio. However this is only one design for a diesel engine. When looking at engines with more valves and different injector locations there are many different designs that increase the efficiency of the engine. There are also ways to modify the piston and give it intake and exhaust squish areas. This affects how the whole engine runs and the intake and exhaust velocity that in produced

Bracco, F. V. (1985). Modeling and diagnostics of combustion in spark-ignition engines (No. CONF-850915-1). Princeton Univ., NJ (USA). Dept. of Mechanical and Aerospace Engineering. Retrieved from https://www.osti.gov/biblio/5976476

Davis, G. C., & Borgnakke, C. (1982). The Effect of In-Cylinder Flow Processes (Swirl, Squish and Turbulence Intensity) on Engine Efficiency — Model Predictions (SAE Technical Paper No. 820045). Warrendale, PA: SAE Technical Paper. https://doi.org/10.4271/820045

Miles, P. C. (2016). Physical Fluid Dynamics in Reciprocating Engines.(No. SAND2016- 8910PE). Sandia National Lab. (SNL-CA), Livermore, CA (United States). Retrieved from https://www.osti.gov/biblio/1390761