Engine/Transmission (1994 - 1998) What is the AFC?

[rnolen]

Forgive me but I don't know what an AFC is? I am not the most knowledgeable TDR member.

Russ

 

[drees1]

The AFC is the Air Fuel control. It is a spring loaded diaphram located on the top rear (towards firewall) side of the injection pump. It is that bulge on the top of the pump. It limits fuel according to boost. Boost pressure is on one side of the diaphram and a spring is on the other. Since the engine is turbo charged it consumes much more air at higher boost levels. The AFC prevents overfueling (and smoke) at low boost (low air flow) conditions. As boost builds, the diaphram in the AFC moves against the spring and allows the rack in the pump to a higher fueling position to match the amount of air. There are many adjustments to the AFC, including changing springs, setting the initial spring load, setting the initial internal position, sliding the whole housing, and bleeding off the boost signal to fool it. All of these have different effects in controling the amount of fuel allowed as a function of boost level. The vendors that sell performance mods have identified the best combination of adjustments and changes to compliment various upgrades.



The 2 simplest adjustments you can make are to slide the whole housing, by loosening the mounting bolts, and to trim the star wheel by removing the big allen head plug on top.