L2501 Engine – INJECTION NOZZLE

Exhaust and noise regulations are becoming increasingly strict, particularly in regard to the reduction of NOx (nitrogen oxides) and particulates.
The two-spring nozzle holder has been developed to reduce NOx (nitrogen oxides) and particulates from direct injection diesel engine exhaust.
Features
The two-spring nozzle holder limits needle valve lift at initial valve opening to throttle the injection quantity.
Main injection occurs when the in-line pressure has increased sufficiently to move the needle valve through its full lift.
The gives the following features.
• Improved engine stability at low and intermediate
speeds.
• Decreased engine hunting and surge.
• Decreased noise at idling.
• Decreased idling speed because of improved engine stability.
• Stabilized fuel injection characteristics from the injection pump and nozzle system, and easier matching of governor characteristics to engine demand.
(1) Nozzle Holder Body
(7) Second Spring
(2) 1st Stage Injection Pressure
(8) Pre-lift Adjusting Spring Seat
Adjusting Shim
(9) Chip-packing
(3) First Spring
(10) Max-lift Adjusting Washer
(4) Pressure Pin
(11) Retaining Nut
(5) Spring Seat
(12) Nozzle
(6) 2nd Stage Injection Pressure Adjusting Shim

First opening pressure
The force of the high pressure fuel delivered by the injection pump acts to push the needle valve up. When this force exceeds the set force of the first spring, the nozzle’s needle valve pushes the first pushrod up and the valve opens. (First opening pressure is represented by point “E” in the bottom left hand figure, and point “A” in the above figure.)

Second opening pressure
When the first pushrod has been lifted through the pre-lift, it contacts the second pushrod. As the set force of the second spring is acting on the second pushrod, the combined forces of both the first spring and the second spring then act on the needle valve, which will not lift unless these forces are overcome.
When the high pressure fuel (ie, in-line pressure) overcomes the combined forces of the first and second springs, the needle valve is again lifted and main injection can begin. (Second opening pressure is represented by point “F” in the bottom left hand figure and “B-C” in the above figure.)

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