Is an Idle Speed of 0.7 Normal?

1 Answers
LaKyle
07/29/25 4:40pm
An idle speed of 0.7 is normal, as the idle speed of a car varies between cold and warm engine states. More cylinders result in lower idle speeds: The idle speed of a car engine is primarily related to the stability of crankshaft rotation. The more cylinders there are, the better the force balance during crankshaft rotation, leading to smoother operation. Typically, a 12-cylinder engine has the lowest idle speed of only 500 RPM, an 8-cylinder engine's idle speed is around 600 RPM, a 6-cylinder engine's idle speed is approximately 600 RPM, and a 4-cylinder engine's minimum idle speed is 750 RPM. However, a 4-cylinder horizontally opposed engine eliminates the need for balance shafts and counterweights due to its horizontally opposed cylinders, allowing it to achieve a minimum idle speed of 650 RPM despite having only four cylinders. Larger displacement leads to lower idle speeds: Generally, the larger the engine displacement, the lower the idle speed. More cylinders naturally result in larger displacement, and with multiple cylinders working simultaneously, the stability is inherently better, allowing for lower permissible RPMs.
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