enginespeedj1939 - SPN 190 - to review

Revolutions per minute of the engine

High-Level Explanation

Revolutions of the crankshaft per minute calculated as minimum crankshaft angle of 720 degrees divided by the number of cylinders.

Some context on engine operation:

In a four-stroke engine, an individual piston fires every 720 degrees (two crankshaft rotations). If you divide that by the number of cylinders, you get a figure that represents the optimal degrees of crankshaft rotation between cylinder firings.

Four stroke meaning the four cycles each piston goes through, this is intake, compression, combustion, exhaust.

During each rotation every cylinder has its own timing for each stroke. So for example on a 4 cylinder engine every 180 degrees a cylinder goes through the combustion cycle while another is seeing intake and another is seeing compression and another is seeing exhaust

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