AFC tuning overrated?

Cummins Driver

Cummins Driver

THE Cummins Driver
Joined
May 16, 2007
Messages
2,405
Alright. My truck hazes a steady haze about any time i accelerate. I can drive it around town without much smoke at all. But any decent acceleration in overdrive at 50-60mph and there is a haze. It does spend most of its time down under 1800rpm with my tight converter and 3:55's, but i thought surely i could get it to accelerate decent without a haze. It was the same with the stock turbo too, so i know its not that. I have tried playing with the AFC. I have backed the pre boost screw waay out. The truck was sick(in valet mode), and cleared up the smoke fast, and only made about 10psi of boost, but it still hazed under light throttle, or rolling into it fast. I flipped the valet switch to full fuel and tried it. It has less smoke if you mash it, but no less than if i just roll into it to begin with. It also didnt spool any faster like i hear a lot of people talking about.

Now, I know the AFC can make a difference on a very heavily fueled truck with a bigger turbo, but so far i have yet to see a condition where it works any better than rolling into the throttle with your foot. I can tell mine spools a touch better if i roll into it instead of just mashing it, but i can do it just as easy with my foot as with the AFC. And i still have the smoke if i want it.

Maybe i dont have enough fuel to notice the difference? Maybe a better turbo would clear my haze up under light loads? So far, the only difference i can make with the AFC starwheel, or pre boost screw is just making the power come on later and more linear in full fuel, and being less powerful in valet mode. Part throttle haze is the same either way.

I have a 0 plate, but that shouldnt make any difference in the part throttle haze in valet mode since the AFC foot never moves back when im in valet.

Ideas? Comments? Suggestions? Id love to see a before and after video of someones truck that AFC tuning made a big difference in.

Eric
 
I would make sure the governor lever is even hitting the afc foot. Just because its hitting the plate dosent mean its hitting the foot. height may need to be adjusted.
 
Its hitting the foot because its cutting the power back when im in valet mode.

Foot also isnt ground or anything.

Eric
 
hope you figure out how it works cuz if you dont like the tune up with stock injectors you are gonna hate it with 5x12's

have you taken it apart and looked at it?

flipped the washers?

look at it and grind what is in the way

if you want the lever to go back further it is possilbe

if you want it to go forward further that is possible too

afc is not overrated - its everything

where is the housing on the pump?
 
It is possible you might need your injectors check just a thaut.

Dale
 
DTanklage said:
hope you figure out how it works cuz if you dont like the tune up with stock injectors you are gonna hate it with 5x12's

have you taken it apart and looked at it?

flipped the washers?

look at it and grind what is in the way

if you want the lever to go back further it is possilbe

if you want it to go forward further that is possible too

afc is not overrated - its everything

where is the housing on the pump?
Click to expand...

I have had it apart. Its in good shape. I havent flipped the washers, but that isnt really needed for anything unless you put a rack plug in it. I did grind the front of the AFC foot's shaft so that it wont hit the front of the housing under full travel.

I have the AFC housing all the way forward, but i can still get the arm back far enough to make the thing sick to drive by backing out the pre boost fuel screw, so i see no need to slide the housing to the back.

I never said i didnt like how it runs. Just that it hazes under much throttle at all. It did the same with my old 160 injectors, so i dont think that is the problem.

Maybe sliding the AFC housing all the way back and leaving the spring pretty loose would be more to my liking? I just dont see how it would be any different than backing out the pre boost screw and having some tension on it.

I also use my valet switch a lot, and i dont want it to be sick in valet mode since that is how i usually run when i pull a trailer.

Eric
 
Hmm, maybe it could be injectors then? Both sets i have had in the truck have had over 150K miles on them.

Maybe i just need to stick my New Era 370's in there and put my 181's back in and see what that gets me for smoke. My New Eras only have probably 5 or 10k miles on them so they should be in good shape. I have never tried them in my truck though.

Do you think pop off pressure is possibly getting low Weston?

Eric
 
I see. Why do you think my New Era 370's would already be weak with just 5 or 10k miles on them?

Eric
 
I dont doubt it, just curious what the cause is? They dont get set high enough before they are sent out, or weak springs or something i assume? Thanks

Eric
 
Smokem said:
I won't directly single any one company out, many I have seen the nozzles are just swapped onto a core body. No changes in opening pressure, no lift added, no lapping, and the paint isn't even removed. If you are the business between the supplier and customer, this should be your job.
Click to expand...

So who can I get injectors from that actually does these things?
 
lenny at ddp has built me injectors

think they still had paint on em tho

but they have always worked great

the guy answering all the questions builds em too

his name is weston

i wonder how many miles one should put on a set before having the pressures checked?

think about how many times that spring gets compressed in only 10k miles
 
back to topic - i dont think that afc tuning is overrated

i like westons idea. he suggested setting them all up the same (the afc) and letting the size of the turbo dictate spring rate

once you get your injectors sorted out i think you are gonna find that there is a lot of power and drivability inside that housing

good luck with it and dont forget to report back

don
 
i dont think you have enough fuel to understand why some of us want to tune the afc, if i have everything full forward, and just roll into the throttle, it is a good bit of smoke, and guess what happens when you mash the pedal?? day turns to night really quick. point is, i want the afc to hold back some fuel down low, i can do that with the go pdeal a little bit, but it is eaiser to drive the truck, and not have to worry about how much to hold the throttle back untill the turbo lights, where that would be the afc's job, hold some of he fuel back until a good amount of boost is obtained, and then add as allowed. it did make a difference in my truck, driving around town it's alot less smokey, but it still can get out of control, i have a couple of things working against me, one is too big of a turbo, and FC delivery valves, i have now realized that hey i dont need this faily large turbo, and goobs of fuel to make decent power on the street. in fact, i am convinced that i have lost power. i have a 66/65/14 HTT turbo on my truck, it does spool decent for a fairly large charger, but im now realizing that i need something smaller that will still flow great, but get up on the boost alot quicker, im thinking about going down to a 64/71/13SS, or maybe even a 62/71/13SS. and i will actually make more power where i need it because there will be more boost down low where is need it. now we can tune that afc even more to the changes in the turbo.i am also going to change the injectors in the truck, probably going to go with a set of New Era 435's. yes it's alot of injector, but with a set of 191 DV's, 64/71/13SS, and some tuning it will be a awsome setup. will report back once i have some more stuff done.

wes
 
wes, our trucks are set up almost exactly the same

i went from ddp 3 (50 lpm) to ddp 4 (55 lpm) approx 5x14 (like a 435)

cept i put the plate in the swap meet as weston suggested (yes, i prolly woulda figured out that i didnt need it after goin in there a few more times)

181's

4k rpm 913 pump

set it at 6.40mm lift 20.7°

so far have tried a 62/65 66/74 and right now am running 64/71

it runs pretty hard - is a lot of fun

oh, right now i have the med spring from tst in there

when i get the twins on it (62/65/13 < 475) prolly be able to get away with the light spring
 
Im still not completely satisfied that my injectors could be bad enough off on pop off pressure to cause that much difference in how it smokes under light throttle. Maybe i would be surprised?

Id like to set them, but i have to drive this thing every day and im not sure who around here can do it. I know its pretty simple to shim them, but i dont have any way to test what BAR they pop off at.

Dont get me wrong. I can make a big difference in the heavy smoke with my AFC, but it seems to always have a decent haze at least when you first get into the throttle. I can tune the afc to where it is pretty much a haze until the turbo lights, and it never just pours the smoke, but it just seems to spool slower, and doesent smoke any less under part throttle loads like hills and taking off.

I may eventually see if i can get my injectors set to the right pop off and go from there with it.

Thanks for the help everyone.

Eric
 
lenny can fix em in a day

throw a stg 3 or 4 tip in em

and shoot em right back to you

priority flalt rate box will get them there in a day for under 10 bux
 
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