What is the minimum cranking speed for a four-stroke diesel engine?

The minimum cranking speed for a four-stroke diesel engine is commonly recognized as 150 rpm. This speed is critical for ensuring that the engine achieves sufficient compression and fuel atomization during the cranking process. At 150 rpm, the engine can generate the necessary pressure within the combustion chamber, allowing for proper fuel ignition.

Cranking at lower speeds may not provide enough momentum for the engine to reach the compression required for efficient fuel combustion. For a diesel engine specifically, which relies on high compression ratios for ignition, inadequate cranking speed can lead to failure to start, as the fuel may not adequately ignite in the combustion chamber. Therefore, maintaining a minimum of 150 rpm during cranking is essential for reliable engine operation and starting.