In order to improve the power of the engine, some refitting shops have modified the camshaft of the engine, among which the high-angle camshaft camshaft (Hi-CAM) is a common modification method. This modification operation is not complicated, but because some modification personnel have insufficient understanding of the working angle and working principle of the cam on the camshaft, the effect of the modification is not obvious and even the performance of the engine is deteriorated.
The high-angle camshaft is relative to the cam working angle of about 240° of the ordinary camshaft, and the cam working angle of the high-angle camshaft can usually reach more than 280°. The large-angle camshaft can extend the opening time of the valve, increase the lift of the valve, enable the intake valve and exhaust valve to open early and close late, and allow more air to enter the cylinder to increase the power of the engine at medium and high speeds Output. For civilian vehicles, a camshaft with a cam working angle below 278° should be selected when refitting, because a camshaft with a working angle greater than 278° will greatly increase the valve overlap angle and increase the power of the engine at high speeds. At low speeds, due to the poor sealing of the cylinder, the idling speed will be severely shaken or even stalled. Such vehicles cannot adapt to daily use and can only be used for competition.