AFC position

madmikeismad said:
Always wondered if it's ok to change to a slightly smaller washer. Is there a chance the AFC rack will get hung up if you let it go too far?
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Smaller diameter or thickness? You definitely wouldn't want to go any thinner. The washer will bend too easily.
 
npe3484 said:
Smaller diameter or thickness? You definitely wouldn't want to go any thinner. The washer will bend too easily.
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I think he means a smaller diameter. There is no point in doing that though. After you take ~.100" off of the barrel the afc no longer limits rack travel as far as I know.
 
bna5017 said:
That's the point of grinding the barrel. After you grind enough off of it, it will no longer be the limiting object of rack travel. The pictures show that after you grind the barrel the washer becomes the limiting factor. Notice how the washer is hitting the afc housing and the barrel is not.
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Thanks. I'm not thinking today.
 
Where do you guys start on the AFC tuning? Smoke screw in and housing forward? Or opposite and back off the smoke.
 
I started with mine in the middle and the smoke screw barely touching the rod.
 
Well, since position doesn't matter, I'd put it in the middle, with the smoke screw in the middle (give or take), and just play with the smoke screw.

Here's one more question: Does the AFC ever limit full rack travel when full forward, or just when it's to the rear? How does taking off .1 suddenly give the rack full travel, with the AFC in any position? All I can think is that it didn't limit the rack's full travel to begin with.
 
Great thread!

While we are talking about the afc foot, how does food height effect fueling? I tried to set mine where it was stock but i could barley see where the stock position was and im not really sure how it will effect fueling.
 
Grinding the barrel would simply give you more air and fuel to play with is what I'm gettin across. I like my plate, starwheel, AFC all forward, but have my screw backed off ~ 1/8 of a turn. smoke is controlable. Certainly noticable power increase.
 
madmikeismad said:
Well, since position doesn't matter, I'd put it in the middle, with the smoke screw in the middle (give or take), and just play with the smoke screw.

Here's one more question: Does the AFC ever limit full rack travel when full forward, or just when it's to the rear? How does taking off .1 suddenly give the rack full travel, with the AFC in any position? All I can think is that it didn't limit the rack's full travel to begin with.
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You have to figure in the fact that your taking the "lip" off of that washer on the diaphram, that allows a little extra travel as well. Also you can gain more travel in the rearward direction by modding both washers and using a longer spring. So you actually gain travel both directions compared to a stock housing.

If you have a stock spring and overtighten it, then you will get binding(which limits travel) so you want to be sure to have the correct spring so thats not an issue.

I start with very little tension on the spring(correct spring for a given application) and with the pre boost screw just screwed in enough to touch the diaphram. That will let you control fueling and give you the maximum amount of travel available from the afc. If you start with the pre boost screwed halfway in then your eating up some of the travel the afc offers. I start with the housing in the middle and see if i still have too much fuel. If so I keep moving it back till the truck is not getting enough fuel. From there you can add preboost fuel with the screw in SMALL ajustments(like 1/4-1/2 turn at a time). Once i get the pre boost set i move on to ajusting the spring tension. I just keep tightening it til i have the best transition into boost.

its a little time consuming, but not rocket science
 
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mathews8pt said:
You have to figure in the fact that your taking the "lip" off of that washer on the diaphram, that allows a little extra travel as well. Also you can gain more travel in the rearward direction by modding both washers and using a longer spring. So you actually gain travel both directions compared to a stock housing.

If you have a stock spring and overtighten it, then you will get binding(which limits travel) so you want to be sure to have the correct spring so thats not an issue.

I start with very little tension on the spring(correct spring for a given application) and with the pre boost screw just screwed in enough to touch the diaphram. That will let you control fueling and give you the maximum amount of travel available from the afc. If you start with the pre boost screwed halfway in then your eating up some of the travel the afc offers. I start with the housing in the middle and see if i still have too much fuel. If so I keep moving it back till the truck is not getting enough fuel. From there you can add preboost fuel with the screw in SMALL ajustments(like 1/4-1/2 turn at a time). Once i get the pre boost set i move on to ajusting the spring tension. I just keep tightening it til i have the best transition into boost.

its a little time consuming, but not rocket science
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I thought smokem said to adjust the starwheel all the way back and stretch the spring accordingly?


Tell me your opinion of a good transition into boost. I'm just getting mine tuned and its crazy how fast and almost smoke free it is.
 
bsmith said:
I got the afc apart but can't get the shaft out. What do I need to do to get it out?
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It has an o-ring that seals and holds it in place. Pry gently on the base where it changes diameter and it should pop out after you slide it out 1/4" or so.
 
White Knight said:
It has an o-ring that seals and holds it in place. Pry gently on the base where it changes diameter and it should pop out after you slide it out 1/4" or so.
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Thanks. Right after I posted, I took a screwdriver, pryed it and popped it out.
 
Hmm,
I guess I'm not high-tech enough to use a jig. I just hook up a small bicycle pump to the AFC on the bench and adjust the star wheel as needed to get full travel at desired air psi setting.

As far as adjusting arm height, I just lower it all the way.

As far as AFC foot profile, I like to grind just a little on the foot to make it flat so it does not cut out fueling as RPM rises, that's what the governor is for in my opinion. With a flat foot, it limits rack travel the same amount regardless of RPM. I also take about 1/8" off the barrel.
 
bsmith said:
I thought smokem said to adjust the starwheel all the way back and stretch the spring accordingly?


Tell me your opinion of a good transition into boost. I'm just getting mine tuned and its crazy how fast and almost smoke free it is.
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You want to move the starwheel AWAY from the diaphram. I call it forward.

The longer the spring the better, as long as it doesnt bind before full travel.

I havent tuned on a twin truck, should be easier than a big single i would think. The way i explained above should work no matter what charger setup your using. Its a little slower doing it that way, but easier if you've never done it before. Keep tweaking, it takes a while. When i swap a charger on my truck i just throw the needed tools in the truck and make small ajustments on the way back and forth to work.
 
Ok that's what I'm doing. I never adjust the starwheel. Its all the way forward, I've just been trying different springs. I always keep my tools in the door to tune as needed. I'm just getting to where I can use my preboost screw since I've found a stiff enough spring.

It def takes time but its rewarding.
 
the reason you go all the way forward with the starwheel is because it relieves the tention off the spring which allow less boost to move the foot.
 
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