A depression is created in the crankcase (12) as the piston moves upwards. The piston (4) moves up the cylinder again and compresses the mixture. All lubricating points are wetted in this process. This over-pressure forces mixture out of the crankcase (12) through the cam housing (not shown in the illustration), via the pushrod passages (11) and the valve gear (10), through the bypass bore (9) and inlet port (2) to the combustion chamber (6). Over-pressure is created in the crankcase (12) when the piston moves down the cylinder. The transfer of the fuel/engine oil and air mixture is controlled by the upward and downward movements of the piston (4). This ensures lubrication of the 4-MIX™ engine without a separate supply of engine oil. This way, part of the fuel mixture constantly flows around all the moving parts (valve gear, crankshaft, cam, piston). Unlike most other four-stroke engines, the valve gear (10) and crankcase (12) on the STIHL 4-MIX™ engine are connected to the inlet port (2) via a bypass bore (9).

Fresh fuel mixture flows through the inlet port (2) into the combustion chamber (6) until the inlet valve is closed again by the cam.

The inlet valve (3) is opened by the cam (not illustrated). Compact construction - attractive design.ADVANTAGESĪs the 4-MIX™ engine makes use of the gasoline-oil mixture for lubrication, it combines the benefits of two-stroke and four-stroke engines. The 4-MIX™ engine is relatively quiet in operation and, like STIHL two-stroke engines, complies with the strict exhaust emission standards. It is therefore very suitable for applications in STIHL portable power tools. Like the time-proven STIHL two-stroke engines, the STIHL 4-MIX™ engine operates reliably at any angle, even upside down. This allows a compact construction without a separate oil reservoir, oil pump and oil filter. As such, it must be run on a mixture of gasoline and engine oil. Unlike other four-stroke engines, the 4-MIX™ engine is lubricated by the gasoline-oil mixture. THE FOUR STROKES OF THE 4-MIX™ ENGINE ARE: The spark plug initiates combustion by producing an ignition spark at the exact predetermined point. The carburetor supplies the correct mixture of air and fuel. Energy is released during combustion of the fuel-air mixture in the cylinder, which is converted into motion via the piston and crankshaft. Like the four-stroke and two-stroke engines, the STIHL 4-MIX™ engine is an internal combustion engine. STIHL provides professional users with the ideal outdoor power equipment solution, offering all the benefits of two-stroke and four-stroke engine technologies combined.

4 stroke combustion