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2nd Gen AFC Modification and Tuning

  
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2nd Gen AFC Modification and Tuning

 
White_Lightning White_Lightning
Guru | Posts: 937 | Joined: 07/09
Posted: 01/30/11
07:51 PM

I’m about to attempt to explain the basics of how an AFC works, and how to modify it to allow maximum rack travel. This may be a little long so bare with me or skip through sections. I’ll start with the basic operating principle behind how it works. The AFC limits the maximum amount of rack travel allowed dependant on the amount of boost pressure the engine is operating under. For the AFC or fuel plate to come into effect you need to be under significant throttle input. I'll try to go through the main pump factors from a no boost situation to a high boost situation.

So assuming you are pedal to the floor: the limiting factor at no to low boost is the "pre-boost" screw, aka the smoke screw as others call it. The adjustment of the screw is also relative to the position of the AFC housing. People often forget to adjust the screw when moving the housing. Others adjust this to gain more smoke. It has no effect on power, but has a lot to do with getting your turbo to light. The adjustment is on the very back of the AFC under a small cover held on by two bolts. Under the cover the screw is locked in place with a jam nut. Turning the screw clockwise into the housing will increase the potential fueling levels before boost is built. Counter clockwise does the opposite. Make sure to tighten the jam nut when you’re done so it doesn’t move. The pre-boost setting usually doesn’t limit power but it might make the truck hesitate just slightly before starting to pull. Backing the screw all the way out and sliding the housing towards the radiator is a decent place to start and will allow you to adjust the housing if the truck fuels to heavily with minimal disadvantages.

Once some boost has been built the starwheel and the AFC spring comes into play. Tightening (counter-clockwise as facing the same direction as the truck or turning the teeth away from the motor) the starwheel increases the tension on the spring which rides on the AFC diaphragm which will require more boost to be built before the AFC arm will move and how much boost is required to allow full fuel. Loosening again does the opposite, and removing all tension would effectively be like sliding the housing forward or turning the pre-boost screw in. Starwheel setting is somewhat relative to personal taste. A tight starwheel will limit smoke but too tight and it will cut into midrange power also. Too loose and the truck will smoke heavily and power may also be reduced because of excess fuel. Changing the starwheel setting is a fine adjustment (maybe +/- 5psi to full travel) for large changes using different springs can be very effective.

Once significant boost is built the AFC allows full fuel and the governor arm is free to ride on the plate. Moving the plate forward or using a different one would allow the governor arm to travel farther and increase rack travel effectively increasing the duration that the fuel is injected. Because boost is already built and most likely the rpms are high enough, (hopefully your setup doesn’t allow full fuel before the engine is ready) the aggressiveness of the plate usually has little effect on smoke levels especially with stock injectors and turbo. This is where max power happens though so an aggressive plate or no plate is usually desirable.

The stock AFC doesn’t always incorporate enough travel to obtain full potential rack travel. Modifications can be made to allow full travel but some may give up a little ability to limit smoke. Careful choice is required. Switching the washers that hold the diaphragm allows additional travel but will not allow the arm to return to its home position and will be like turning the pre-boost screw in a few turns. I prefer to modify the washer by grinding the cup flat, or to replace the cupped one with a flat one, which allows both. Another common practice is to grind the tip of the AFC foot flat (only take off the angle, do not grind any more than you have to, just make it flat), and grind the forward part of the arm's barrel by .100".

I personally try to set them up so that just a haze is all that is seen throughout the RPM range. My personal pickup is extremely overfueled as of right now, and blows coal like nobody's business. But as soon as I get more air I will be completely retuning it.

A final note, the AFC is very easy to disassemble and put back together, just remember if you grind something to keep it cool. I like to grind for 5 seconds and dunk the part in water.




I added these pictures up here for easy reference while reading the mods.


Here is a break down of the parts of the AFC:
AFC6

AFC

AFC1

Here is a fully disassembled AFC, kinda lined up like how it goes together.
AFC2

Here is an AFC and fuel plate testing jig. It simulates the parts on a pump, but with the under side exposed so you can see how it works. As you can see in this first picture, at no boost the AFC arm is well back from the fuel plate. This is why I say it doesn't matter what your plate profile is at low/no boost pressures, because the AFC won't allow the pump to fuel to what the plate limits at.
AFC3

Here is the same setup but with regulated shop air applied at 25psi to the AFC to simulate boost. As you can see, the AFC arm has moved forward exposing the fuel plate. Now the plate profile comes into play (this is a #100) and controls the maximum amount of fuel available to the engine.
AFC4  
Logan
1995 12 valve Cummins 6.0L, 5 speed, 4x4, 600hp Valair Clutch. Air Dog 4GHD lift pump, no fuel plate, 2095 rack plug, 024 DV's, pump benched at 440cc, SDX 5x.014 injectors, Hamilton 181/210 cam and HD pushrods, Stage 2 Port job, 5 angle valve job, 60lb valve springs, ARP studs, O-ringed head, .020" over head gasket, coated pistons, balanced bottom end, Fluidampr, PDI exhaust manifold, homemade intake manifold, 63/68/0.80 over 80/92/1.32 compound turbos.

01 24 valve 01 24 valve
Enthusiast | Posts: 317 | Joined: 11/09
Posted: 01/31/11
04:41 PM

well that will help me emencly when i switch transmissions and am ready to do some major pump work i wanna make mine so my turbo lights up quickly and has even amount of fueling throughout my rpm's and as for smoke a little would be nice but only say if a put it in a high gear and just lugged it and put the pedal to the floor that kind of smoke quite a bit but not to much that it will wreck my performance of my truck  
2001 dodge ram 2500 ext cab short box 5 speed 4 inch down pipe into 5 inch strait pipe exhaust into 6 inch chrome dual aussie stacks, 90hp injectors with 200hp tips, quadzilla adrenaline tuner with monitor , ,  bd lift pump, AFE stage 2 cold air intake, ARP head studs, ATS three piece exhaust manifold with t4 flange,Garrett ta45 turbo southbend dual disc 750hp clutch with 1 3/8" input shaft

White_Lightning White_Lightning
Guru | Posts: 937 | Joined: 07/09
Posted: 02/03/11
06:26 PM

If you get it set so your turbo lights the fastest, you won't be able to black out an intersection lugging it out.  
Logan
1995 12 valve Cummins 6.0L, 5 speed, 4x4, 600hp Valair Clutch. Air Dog 4GHD lift pump, no fuel plate, 2095 rack plug, 024 DV's, pump benched at 440cc, SDX 5x.014 injectors, Hamilton 181/210 cam and HD pushrods, Stage 2 Port job, 5 angle valve job, 60lb valve springs, ARP studs, O-ringed head, .020" over head gasket, coated pistons, balanced bottom end, Fluidampr, PDI exhaust manifold, homemade intake manifold, 63/68/0.80 over 80/92/1.32 compound turbos.

01 24 valve 01 24 valve
Enthusiast | Posts: 317 | Joined: 11/09
Posted: 02/04/11
10:17 PM

well then ill just make it so my turbo or by then turbo's wont light quite as quick i had a license plate on my old dodge saying if this cummins aint smoking it must be broken so at some point i wana put it on this truck lol and i cant put it on till it blows smoke or it must be broke lol  
2001 dodge ram 2500 ext cab short box 5 speed 4 inch down pipe into 5 inch strait pipe exhaust into 6 inch chrome dual aussie stacks, 90hp injectors with 200hp tips, quadzilla adrenaline tuner with monitor , ,  bd lift pump, AFE stage 2 cold air intake, ARP head studs, ATS three piece exhaust manifold with t4 flange,Garrett ta45 turbo southbend dual disc 750hp clutch with 1 3/8" input shaft

White_Lightning White_Lightning
Guru | Posts: 937 | Joined: 07/09
Posted: 02/07/11
09:07 AM

If that's what you want to do, leave the smoke screw turned in a little bit but set the starwheel so when you build boost it clears up to just a haze of smoke.  
Logan
1995 12 valve Cummins 6.0L, 5 speed, 4x4, 600hp Valair Clutch. Air Dog 4GHD lift pump, no fuel plate, 2095 rack plug, 024 DV's, pump benched at 440cc, SDX 5x.014 injectors, Hamilton 181/210 cam and HD pushrods, Stage 2 Port job, 5 angle valve job, 60lb valve springs, ARP studs, O-ringed head, .020" over head gasket, coated pistons, balanced bottom end, Fluidampr, PDI exhaust manifold, homemade intake manifold, 63/68/0.80 over 80/92/1.32 compound turbos.

01 24 valve 01 24 valve
Enthusiast | Posts: 317 | Joined: 11/09
Posted: 02/07/11
01:45 PM

alright do you think it would be wise of me to just take my truck to the diesel shop near me and get them to tune it rite for what my transmission cant take for now ?  
2001 dodge ram 2500 ext cab short box 5 speed 4 inch down pipe into 5 inch strait pipe exhaust into 6 inch chrome dual aussie stacks, 90hp injectors with 200hp tips, quadzilla adrenaline tuner with monitor , ,  bd lift pump, AFE stage 2 cold air intake, ARP head studs, ATS three piece exhaust manifold with t4 flange,Garrett ta45 turbo southbend dual disc 750hp clutch with 1 3/8" input shaft

mark5.9 mark5.9
User | Posts: 50 | Joined: 01/11
Posted: 02/08/11
10:47 AM

Put it this way if your trany's going to go out its going to go no matter what if its on its way out, If your just going to do the AFC and fuel plate its not going to finish off a trany. I take it though you have a Auto and not a Manual right. And if so of course the Manual can take alot more then the Auto cause of there non stop histroy of problems but the auto will be fine for awhile but not matter what adding HP or not that auto has to be fixed sometime or another. Now 350Hp and above its time to work on the trany. As for the liesence plate it might be easier to get some new plates  

White_Lightning White_Lightning
Guru | Posts: 937 | Joined: 07/09
Posted: 02/08/11
04:37 PM

The AFC won't control your maximum horsepower, that's what the fuel plate is for. A diesel shop will likely put the AFC back to stock settings, they don't like aftermarket stuff unless you're talking about an aftermarket shop.  
Logan
1995 12 valve Cummins 6.0L, 5 speed, 4x4, 600hp Valair Clutch. Air Dog 4GHD lift pump, no fuel plate, 2095 rack plug, 024 DV's, pump benched at 440cc, SDX 5x.014 injectors, Hamilton 181/210 cam and HD pushrods, Stage 2 Port job, 5 angle valve job, 60lb valve springs, ARP studs, O-ringed head, .020" over head gasket, coated pistons, balanced bottom end, Fluidampr, PDI exhaust manifold, homemade intake manifold, 63/68/0.80 over 80/92/1.32 compound turbos.

01 24 valve 01 24 valve
Enthusiast | Posts: 317 | Joined: 11/09
Posted: 02/08/11
06:30 PM

well im pretty sure thats wat they are is more of a performance kinda of shop ill look into that but uh mark5.9 i do have and auto tranny but its in great working condition its not on its way out the truck only has 156000km on it and like i said before i will be swapping it out in the next year or so for a nv5600 6 speed so wat your saying is i can basically do the highest mods to the pump and my transmission will still be fine  for awhile  
2001 dodge ram 2500 ext cab short box 5 speed 4 inch down pipe into 5 inch strait pipe exhaust into 6 inch chrome dual aussie stacks, 90hp injectors with 200hp tips, quadzilla adrenaline tuner with monitor , ,  bd lift pump, AFE stage 2 cold air intake, ARP head studs, ATS three piece exhaust manifold with t4 flange,Garrett ta45 turbo southbend dual disc 750hp clutch with 1 3/8" input shaft

White_Lightning White_Lightning
Guru | Posts: 937 | Joined: 07/09
Posted: 02/09/11
10:35 AM

If you want to keep the tranny in good working condition, I wouldn't do anything more than slide the fuel plate forward. Maybe a mild grind like a #10 and leave it slid back some but that's it. And tune the AFC and tighten up the governor springs.  
Logan
1995 12 valve Cummins 6.0L, 5 speed, 4x4, 600hp Valair Clutch. Air Dog 4GHD lift pump, no fuel plate, 2095 rack plug, 024 DV's, pump benched at 440cc, SDX 5x.014 injectors, Hamilton 181/210 cam and HD pushrods, Stage 2 Port job, 5 angle valve job, 60lb valve springs, ARP studs, O-ringed head, .020" over head gasket, coated pistons, balanced bottom end, Fluidampr, PDI exhaust manifold, homemade intake manifold, 63/68/0.80 over 80/92/1.32 compound turbos.

01 24 valve 01 24 valve
Enthusiast | Posts: 317 | Joined: 11/09
Posted: 02/09/11
11:15 AM

ok then thats wat ill do for now slide the plate forward then tune the afc so my turbo lights quickly now how come i should tighten up the governor springs i want my truck to be ready for this summer i got a friend with a stock nissan 240sx and he thinks his car is the fastest thing in the world and i really want to put him in his place this drag season.  
2001 dodge ram 2500 ext cab short box 5 speed 4 inch down pipe into 5 inch strait pipe exhaust into 6 inch chrome dual aussie stacks, 90hp injectors with 200hp tips, quadzilla adrenaline tuner with monitor , ,  bd lift pump, AFE stage 2 cold air intake, ARP head studs, ATS three piece exhaust manifold with t4 flange,Garrett ta45 turbo southbend dual disc 750hp clutch with 1 3/8" input shaft

01 24 valve 01 24 valve
Enthusiast | Posts: 317 | Joined: 11/09
Posted: 02/09/11
11:20 AM

oh and should i get a 3500rpm governor spring so my truck fuels more at the higher rpms cuz thats were im afraid ill lose my ground ?  
2001 dodge ram 2500 ext cab short box 5 speed 4 inch down pipe into 5 inch strait pipe exhaust into 6 inch chrome dual aussie stacks, 90hp injectors with 200hp tips, quadzilla adrenaline tuner with monitor , ,  bd lift pump, AFE stage 2 cold air intake, ARP head studs, ATS three piece exhaust manifold with t4 flange,Garrett ta45 turbo southbend dual disc 750hp clutch with 1 3/8" input shaft

White_Lightning White_Lightning
Guru | Posts: 937 | Joined: 07/09
Posted: 02/10/11
07:17 PM

A bone stock factor 240sx runs mid to high 15's in the quarter. You won't catch him with a stock tranny and basic mods. To tighten up the governor springs, pull the shutoff solenoid off the side of the pump, then the lever that it attaches to, and you'll see a plug that can be removed with a 7/8" socket. It'll have a tamper-resistant wire over the top of it, just cut that. Use a 7/8" socket on the alternator to turn the engine over until you see a stud and washer with a nut on it with a slot running diagonally across the top of the nut. put a screwdriver in the slot and turn it to the right, you'll feel it click as you turn it, tighten it up three clicks. Then turn the engine over until you see the same thing on the other governor weight, and tighten it up three clicks, reassemble and you're good to go. They don't make a 3500 RPM GSK, only 3000 4000 and 5000. I would go with the 4000 kit and get some 60lb valve springs and you'd be set for that. Governor spring kits are awesome on these pickups!  
Logan
1995 12 valve Cummins 6.0L, 5 speed, 4x4, 600hp Valair Clutch. Air Dog 4GHD lift pump, no fuel plate, 2095 rack plug, 024 DV's, pump benched at 440cc, SDX 5x.014 injectors, Hamilton 181/210 cam and HD pushrods, Stage 2 Port job, 5 angle valve job, 60lb valve springs, ARP studs, O-ringed head, .020" over head gasket, coated pistons, balanced bottom end, Fluidampr, PDI exhaust manifold, homemade intake manifold, 63/68/0.80 over 80/92/1.32 compound turbos.

01 24 valve 01 24 valve
Enthusiast | Posts: 317 | Joined: 11/09
Posted: 02/10/11
08:59 PM

well i think i might have a chance at him he aint a very good clutcher lol so this process doesnt involve me going inside the pump does it and when u say turn the engine overdo you mean run it ? if i go buy a 4000k governor spring i wont actually go near that i wont take the truck past 2800rpm might take it to 3000rpm but nothing more than that so does that mean i dont have to get the 60lbs valve springs ? is there some pictures you could send to kinda of help like maybe off your engine ?  
2001 dodge ram 2500 ext cab short box 5 speed 4 inch down pipe into 5 inch strait pipe exhaust into 6 inch chrome dual aussie stacks, 90hp injectors with 200hp tips, quadzilla adrenaline tuner with monitor , ,  bd lift pump, AFE stage 2 cold air intake, ARP head studs, ATS three piece exhaust manifold with t4 flange,Garrett ta45 turbo southbend dual disc 750hp clutch with 1 3/8" input shaft

01 24 valve 01 24 valve
Enthusiast | Posts: 317 | Joined: 11/09
Posted: 02/10/11
09:02 PM

ive gotta have a pretty close chance at beating him cuz on my old 92 5p speed ext cab long box i ran 18.5 no brake boost then i did a run with brake boost but i launched outa of the hole like a bullet but then my clutch slipped and that was the end of that so this trucks gotta have a even better chance that my old one did  
2001 dodge ram 2500 ext cab short box 5 speed 4 inch down pipe into 5 inch strait pipe exhaust into 6 inch chrome dual aussie stacks, 90hp injectors with 200hp tips, quadzilla adrenaline tuner with monitor , ,  bd lift pump, AFE stage 2 cold air intake, ARP head studs, ATS three piece exhaust manifold with t4 flange,Garrett ta45 turbo southbend dual disc 750hp clutch with 1 3/8" input shaft

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