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Old 03-17-2017, 06:51 PM   #1
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fuel plate

I did it!!

finally, after a number of years wondering how much better life would be if i just moved that little fuel plate forward, i did it.

i took out the 4 screws that hold down the AFC. one of them is a tamper proof screw, but an easyout worked like a champ getting it out.



after the cover came off, it exposes the fuel plate.



the plate was dead in the middle of the adjustment. i loosened the 2 screws holding it and pushed it forward as far as it would go. it doesn't move much. maybe an 1/8 of an inch.

here it is with the screws tightened back down with the plate forward.



after closing it back up i took it out for a test drive. maybe its better. hard to say. acceleration is alright. still slowed down on grades, so hard to say its much different. it isn't worse than when i started.

if this is all the difference it makes, i should have done it a long time ago.
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Old 03-17-2017, 07:45 PM   #2
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Be very conservative on moving the fuel plate. There are a couple of threads on 4BT swaps by folks who created a runaway conditions on their 5.9's by moving it too far.
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Old 03-17-2017, 10:31 PM   #3
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hot diggity dam Tango!

thanks for the words of wise. since your post, i've been in deep learn mode about the AFC and tuning it and the P pump.

that AFC is coming back off tomorrow for more testing.

my bus has an accelerator like a brick. on my way back from the last test run it takes some much force that i broke the cable off the pedal mount. (not the first time its done that)

after moving the plate today and test driving, it still started accelerating like a brick and i didn't notice much change. however, there was a sweet spot on the pedal, once i passed it, i thought the truck was running away, but no, the effort on the pedal just decreased and it got real easy to accelerate.

now after my reading, i think the pushing that plate forward helped my post boost acceleration. now, i think i need to back off the diaphragm pressure of the smoke screw and increase the pre boost fueling with the star wheel.

now it makes sense to me

That AFC is coming off tomorrow for some more changes.

this "read me first" thread on a cummins forum is chocked full of great links and info for tuning your diesel.

Beginners Thread - Read First! - Dodge Cummins Diesel Forum
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Old 03-17-2017, 10:37 PM   #4
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sounds similar to the navistar... in navistar they call it the anti smoke screw.. but in the end I believe the star screw is the pre-turbo spooling fueling... I would think you might want to boost that a little but not a lot..just enough to maybe help the turbo spool faster.. as you dont want to over-fuel when theres no air to get a good burn.. - alas black smoke and im guessing less complete combustion. so longer turbo spool time? though your bus could roll coal with that turned up!.

-Christopher
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Old 03-17-2017, 11:04 PM   #5
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i had never thought about tuning before until i felt the different pedal today.

from one of those links it said that a stock turbo probably doesnt spool up until 1800 rpm. for lack of knowledge in adjusting the pre turbo boost, they just stay that way.

that AFC is coming off tomorrow for some changes.

rolling coal isn't my goal. the bus has never been a smoker. i think that means its time to run the fuel a bit richer than its been and make some power.
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Old 03-18-2017, 01:06 AM   #6
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here's my plan for tomorrow i'm doing some reading here and just cut and paste steps for me to remember tomorrow.

afc mods (lots of pics) - DieselRam.com

allows greater rack travel -
replace fat washers with fender washers
remove shaft
shorten foot

This controls the 0 boost fueling, the further in the screw the more tension it puts on the afc spring, allowing more fuel to come on with no boost.

remove smoke screw cover
back the smoke screw out

adjust starwheel spring with air pressure. 20psi - half extension, 40 psi, full travel

reinstall AFC pushed in the forward position.

tighten up the smoke screw, the tighter it gets, the more fuel you get a 0 boost.
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Old 03-18-2017, 05:09 AM   #7
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I'm not sure what the stock timing is on that, often when up up the fuel you may be able to bump the timing a bit too.. I can't remember what trans you have, careful on power adding if it's a 545.. too much low end on it wiltg low rpm results in slippage and heat.

Looking forward to this to see what you come up with
Christopher
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Old 03-18-2017, 04:45 PM   #8
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well worth the investment of $5 in parts.



i got the AFC back off today and took it apart. getting through those tamper screws is slow. the internet says you can pound the right size torx into it and reuse the screws but i wasn't so lucky. an old fashion impact driver and a hacksaw did the trick for me.




i took the foot out and ground down the end marked with black. the marker was about 1/8", i ground off maybe a third of that.




i installed the new washers and bolts and reassembled the AFC.



put it all back together and took it out for a test run.


so far, so good. still no smoke, so i think i need to turn the starwheel a bit more to let more fuel in. at first the throttle wouldn't move all the way to full fuel. i loosened the star wheel (which is suppose to increase fuel with boost) until the air compressor could move the foot all the way over to full fuel, but its still pretty tight. and no smoke. if the spring was slack, it should roll coal.

the smoke screw is almost all the way in. there is still some room for adjustment, but not much.

test driving the bus was a marked improvement on the feel of the pedal. it does not feel like a brick when you push the accelerator. its lighter, but i would like it lighter still.

the bus almost held its speed going up and down some mild hills, better than before. the bus felt capable of the speed, instead of barely getting there. in fact there was a bit of throttle cable left at WOT. no need to be stomping on the pedal.

egt temps range from 700 to 1300. uphill wot was 1300* coasting downhill was 700*. egt response is amazingly fast to letting your foot off the pedal too. that 1300 comes down instantly with less pedal.

more experimenting tomorrow. i need to loosen that star wheel a bit to see some smoke.
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Old 03-18-2017, 05:38 PM   #9
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Change the governor springs to get rid of the slow brick feeling. The pedal is much lighter with a 3000 rpm spring.
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Old 03-18-2017, 08:17 PM   #10
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i got one more test in before i lost daylight today.

with the smoke screw almost all the way in, i get a healthy black cloud behind me for about 2 seconds and then it clears up as i stomp on the throttle.

the star wheel is as loose as it will go. a smaller spring would be the next step.

i'll back off the smoke screw a hair tomorrow and probably call it good.

the truck is not timid anymore. you push the pedal and she goes. you feel like you could merge into traffic without any issue. its a much better feel on the pedal and transmission. less slack and slop if that makes sense.

i'm pretty happy. now if it only lasts!
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