AFC

smokinVE

smokinVE

$$+VE=NO HP
Tryin to reduce/get rid of my low rpm smoke. Has anyone tried on of those 2:1 ratio boost elbows in their afc line? I have the silver spring in (which I think is the stiffest spring? correct me if I'm wrong). I've tried many different setting on the start wheel. Top of the AFC housing has been machined to let the pin come further up. I do have a very aggressive fuel pin. I switched it out to the stock one but that made the truck a dog. Plus didn't reduce smoke by much.
 
I will be doing an adjustable boost elbow to mine here shortly. I have heard a few people doing what you want and liking the results.

I have always heard from the old guys that the Green/Red (which I have had in all of my 92-93s) was stiffest. I never tested them though
 
The Hungry Diesel has some stiffer AFC springs. I don't know what application they're from but they are about twice as stiff as stock IIRC. I have one and it greatly reduces low end smoke, does about the same thing as a 2:1 boost reducer would I think.
 
The hungry diesel has a stiffer spring, might help you out. Haven't tried it, but if it is stiffer it would be nice on a hot pump.

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Looks like I typed to slow and fatty beat me.
 
I talked to Eric. He said his spring isn't much stiffer than the one he sells. I'll start gathering stuff to put an adjustable regulator in my AFC line. I'll report back with my findings once I get it all done.

David I think is saying to use the primary so it takes longer to start pushing air into the AFC. Makes since to me.
 
I've got a stock 215 p7100 afc spring in mine. Works pretty well. I forget where it starts fueling at but it lined up with what I wanted at the time.
 
smokinVE said:
I talked to Eric. He said his spring isn't much stiffer than the one he sells. I'll start gathering stuff to put an adjustable regulator in my AFC line. I'll report back with my findings once I get it all done.

David I think is saying to use the primary so it takes longer to start pushing air into the AFC. Makes since to me.
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I've used a standard issue Boost-Fooler (the type with two adjustments: 1 - for the initial spring-loaded ball, and 2 - adjustable bleed-port downstream from the 1st).
Using a manually set (regulated) air source, one can adjust the thing so that you can roughly come up with up a 2/1 ratio (60 in / 30 out) for example. It works, but is a PITA when you try to synchronize it with the AFC spring, etc.

I've found powering the AFC with the primary of twins to be easier seeing as you're now working with a lower pressure to start with compared to that at the intake log with twins.. You still have to dial-in the AFC spring, but it's much easier IMO. Of course, this is all assuming one is running stupid-big injectors, ect and you're trying to clean up Low ~ Moderate boost smoke when leaning into the throttle.
 
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Silver spring seemed stiffer than a red/green spring so that's what I ran in my old 14mm. I actually flipped my starwheel upside down so the spring would sit up higher and have more tension instead of having the groove on the starwheel to sit farther down in. It was tight enough that I it was tough to get the AFC cap back on. It helped but that pump was still a heavy fueler on the bottom end.
 
oldestof11 said:
I will be doing an adjustable boost elbow to mine here shortly. I have heard a few people doing what you want and liking the results.

I have always heard from the old guys that the Green/Red (which I have had in all of my 92-93s) was stiffest. I never tested them though
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I was told by a local fuel injection shop that, of the two factory springs, green/black for the non i/c and green/red for the i/c motors, the green/black one is the stiffest. The silver spring they gave me was said to be the stiffest of the 3. I actually don't have it in my Giles pump, but in my original/spare pump. I should pull the top on this Giles pump and see which one he put in there. If not a silver one, I'll swap them. If it's any other color than I've seen, I'll assume custom and leave it as is. I never asked him among many phone conversations. Don't know how likely that would be though. Only one way to find out.

BC847 said:
If you're running twins, power the AFC by the primary.
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I like it!
 
The non i/c Silver spring is fairly stiff.... our spring is twice as stiff as the i/c green/pink? spring.... but if one is having a lot of issue with a non i/c spring.....a stiffer spring isn't going to be the answer.


A few things. Is your smoke from minimal boost up to full boost? Or zero boost up? Usually the case is zero boost up. No afc tuning will help this (spring wise).


A 5/32" drill bit is 1 thou smaller than the factory slide pin (works great, won't leak, and will actually slide better). Pull off your afc housing.... there is a lot of "afc housing" material one can cut away.

On the "zero boost" side of the afc housing (where the afc lever touches the afc housing at zero boost). Grind away on the inside of the housing itself, also the afc lever's "ears".

Doing things like this..... I run a drill bit slide pin that is (IIRC) a little more than a 1/4" longer than the longest one from Bosch. Then use the spring to your choice, custom grind your fuel pin (you'll have to go aftermarket). Which brings up another point.... if one is running a ground stocker, that's a lot of the problem. They allow the slide pin out quite a bit on the deep side at zero boost.

And then.....if twins, run off primary (like BC stated).



I went from over 40 psi in "valet" mode with the longest slide pin from Bosch to about 25psi after these mods.


Which, something to think about.........see how much you make in "valet" mode. Now.... this shows that the stiffer springs really aren't the original culprit.... we are usually flooding things out due to the amount of movement of the slide collar, at zero boost.
 
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