Competition AFC Arm Modification

[WShupe]

I'm just wondering if anyone else has played with afc arm on the P7100. About 2 weeks ago, I modified a friends 913 pump. Let's say it was a little experiment. I noticed if you lay the AFC housing upside down with a #0 plate also upside down, in it's full forward position, the AFC arm does not have enough travel to let the governor arm reach the plate, thus not allowing full fuel. I noticed previously that a #10 plate seems to spool better 2/3's ahead, rather than fully forward. And therefore the AFC arm is the limiting factor. What I did, was remove the foot of the AFC arm facing rearward. I ground the foot off until it was flush with remaing surface of the arm. The pump now has a #0 plate full forward, flat AFC arm, AFC spring (PDR-heavier one) full forward, smoke screw backed all the way out. The truck is stock except an 18. 5 exhaust housing and the pump mods. Spool up with 18. 5 is actually as quick as the 12 before the modification, and it makes 39lbs of boost. It will smoke, but not as bad as I expected. I have now since done it to 2 trucks. No problems yet, just . Does this sound like a good idea, or am I just crazy?



Thanks, Weston

 

[WShupe]

Sorry, I thought about it and I had to add a little more info on my theory. And by no means do I think I'm the first one that thought of this. I may just be in the dark. OK, so the governor arm is held back by the AFC arm until enough manifold pressure is produced to move the AFC arm forward. So in theory by removing the AFC arm material, the governor arm will move freely the distance of material removed, adding much more fuel off idle, and at low boost situations. And adding the same distance of rack travel until the governor arm hits the plate, that is if you have one, wink-wink Mr. Garmon. The truck is also equipped with 3k governor springs, but the timing, injectors,turbo(compressor side), and driveline are all stock. No, I do not have any dyno numbers yet, the stock clutch cannot even begin to keep up.



Thanks again, Weston

 

[Swayse]

Or, you could just take the arm off and take out the plate.

 

[Jim Fulmer]

I'll add a little here as a thought! If running plateless or AFC arm less is better don't you think I would do it!



There is more to an AFC than meets the eye, there is a ton of tuning tricks in it, in the first post there is some data to start with, if you or anyone else will take an AFC and hook it up to regulated shop air (to simulate boost) then play with different things you will learn allot.



Jim