Exactly what does the AFC do and how does it work.

[Dan_69GTX]

Can anyone explain what the Air Fuel Control is, how it works and what it does?



Or is there a link I can go to that explains this?



Thanks!

 

[Jeff H]

It prevents over fueling when there is not enough boost. For the EPA it keep black smoke to a very small amount.

But as far as how it does this? Some one else will have to explain. I also am wan'ting to know how it works.

 

[SLang]

I notice you guys don't have plates and I can not find any pictures so took a few seconds and threw one together. But I can not get it to go. Read on And I'll get it later.



First look at how a plate is designed. Notice it has a slot in the top and some type of curved plate extending down into the pump. The curve dictates full rack (part that adds fuel) travel. So the after manket plates adjust this curve for more fuel. Now for what you want. The AFC has a "dog" or "ear" that extends into the slot in the plate. If you press all the way on the accelerator the rack comes back and touches the "dog". If you have enough boost the "dog" moves free and the rack travels till it hits the fuel plate. If it does not have enough boost, the dog will not let the rack travel any farther until boost is achieved. At that point the rack is allowed to move all the way to the plate.



Now on the top side of the "dog" is a diaphram (something for air to press on). On one side there is boost signal and the other a spring. The spring applies force agianst the travel of the rack and is what keeps the rack from moving all the way. The boost presses agianst the spring in the direction of rack travel. Thus more boost, the more more pressure the diaphram has on it and the less resistance the rack has to moving aloowing the rack to travel farther.



Move the star wheel adjust preload on the spring. By cranking the star wheel in you preload the spring with pressure. This means it will take more boost before the diaphram starts to move.



If you take the spring out you have no resistance to rack travel. When you step on the accelerator it puts all the fuel you require (from pedal placement) to the cylinders.



If you put a heavy spring in you have a large resistance to rack travel. When you step on the accel. the rack touches the "dog" attached to the diaphram. The rack can only travel this far no matter where the pedel is. When boost builds it starts to put pressure on the spring and relieve resistance on the rack. When the boost completely overpowers the spring the diaphram allow the rack to move with pedal placement.



EDIT: The server annoyed me so go here.



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